Maintaining lightly used car -- idle 10 minutes/week?

[Muse]

Yes, that Mobil 1 Full Synthetic is a Group III+, it's a good oil but it ain't no PAO Group IV oil. As for the oil drain plug, though you really should use a new washer when replacing it, I'd say the most important thing you can do is use a torque wrench when tightening.

I have a torque wrench, had it a long time, don't know if I've ever used it, in fact. I thought it was for torquing wheel lug nuts. Can I use it on the drain plug? Am I looking to get a specific torque? I can still crawl under the car and tighten that drain plug... The torque wrench is 1/2" drive, has a scale on it, it's totally analog, goes up to 140 foot-pounds. Don't know how high I could crank it! Gotta see if I can work it with an 11/16" socket somehow.

Edit: Looking, I see I have 11/16, 3/8" drive sockets (short and long, although I used a box end wrench the other day). So, to use the torque wrench I'll need either a 1/2" drive 11/16" socket (assuming that's the right size, I guess O'Reilly can tell me from their data lookup), or get a 1/2" to 3/8" adapter. What torque do I want?

Edit2: I'm definitely going to have my AC diagnosed professionally.

Edit3: Actually, I have the previous drain plug and a couple of sockets that would seem to work. I used an 11/16" box wrench the other day but the 1/2" 19mm and 3/4" sockets I have seem to have a decent grip on the plug. Presumably I can use either without stripping the plug, or does it matter that I use the proper socket, whatever that is? Online it says that 3/4" is approximately 19mm so guess it doesn't matter which I use.

 

[Zenmervolt]

I'd say the most important thing you can do is use a torque wrench when tightening.

A torque wrench for an oil drain plug? You're joking, right? That's one of the most ridiculous things I've ever heard. A person would have to be utterly incompetent to need a torque wrench to know how tightly to install a simple drain plug.

ZV

 

[tortillasoup]

A torque wrench for an oil drain plug? You're joking, right? That's one of the most ridiculous things I've ever heard. A person would have to be utterly incompetent to need a torque wrench to know how tightly to install a simple drain plug.

ZV

Some cars use aluminum oil pans, I've seen far too many stripped oil pans with wide variety of torque specs. If you don't use a torque wrench, there is no incentive to look up the torque spec, therefore the person torquing the bolt is just guessing how much torque it needs. All the dealerships I've been to use a torque wrench on wheels and on oil drain bolts, let alone the other parts that are typically installed on a car.

The torque wrench is 1/2" drive, has a scale on it, it's totally analog, goes up to 140 foot-pounds. Don't know how high I could crank it! Gotta see if I can work it with an 11/16" socket somehow.

You can google the torque spec for the drain bolts on your car, I always do it when ever doing an oil change or rotating/changing the tires. As for your torque wrench, it's a good torque wrench (Sounds like a split beam) but the problem is, torque wrenches typically aren't useful/accurate @ 20% or less of their scale. So on a 100ft-lb torque wrench, you can't use it for torquing bolts less than 20ft-lbs. You'd have to use a smaller scale torque wrench like a 75ft-lb torque wrench as the torque drain bolts are typically 15-25ft-lbs. You can obtain another split-beam torque wrench off ebay for like less than $20 and it should basically always be accurate unlike the "clicky type" which need frequent re-calibration.

 

[Zenmervolt]

Some cars use aluminum oil pans, I've seen far too many stripped oil pans with wide variety of torque specs. If you don't use a torque wrench, there is no incentive to look up the torque spec, therefore the person torquing the bolt is just guessing how much torque it needs. All the dealerships I've been to use a torque wrench on wheels and on oil drain bolts, let alone the other parts that are typically installed on a car.

It's a drain bolt. You tighten it until it's snug and stop. If you don't have enough feel to avoid stripping out a bolt, you shouldn't be working with tools at all.

The bolts strip out when people get obsessed with torque specs and crank down hard on the bolt. All the OP needs is a basic box-end wrench and to know enough not to crank down on the bolt. It's not rocket science.

Torque wrenches are for things like head bolts, internal engine bolts, and suspension bolts. If you need one for an oil drain plug, you don't have any business working on a car.

ZV

 

[tortillasoup]

It's a drain bolt. You tighten it until it's snug and stop. If you don't have enough feel to avoid stripping out a bolt, you shouldn't be working with tools at all.

The bolts strip out when people get obsessed with torque specs and crank down hard on the bolt. All the OP needs is a basic box-end wrench and to know enough not to crank down on the bolt. It's not rocket science.

Torque wrenches are for things like head bolts, internal engine bolts, and suspension bolts. If you need one for an oil drain plug, you don't have any business working on a car.

ZV

Some people have lots of hand strength and don't know when "enough is enough". Also you miss the point about the aluminum oil pans and the varying torque specs. It's super easy to strip out the drain plug by over tightening it. Most people don't work on cars everyday and don't have a really good feel for how much torque a given object needs and can/will easily over/undertighten it.

Better safe than sorry. It's not difficult to use a torque wrench and once you use it, you'll know you did it correctly.

 

[Zenmervolt]

Also you miss the point about the aluminum oil pans and the varying torque specs.

No, I don't. I've never worked on a car that didn't have an aluminum oil pan. And you'd have to be a ham-handed sub-moron to strip the threads from over-tightening an oil drain bolt. In fact, most of the stripped oil drain bolts I've seen are from dealerships, so apparently the torque wrench doesn't help that much.

The times I've seen things get stripped, it's from cross-threading the drain bolt and a torque wrench doesn't solve that.

A torque wrench is overkill for a drain bolt. To call it the "most important thing" is just laughable.

ZV

 

[tortillasoup]

No, I don't. I've never worked on a car that didn't have an aluminum oil pan. And you'd have to be a ham-handed sub-moron to strip the threads from over-tightening an oil drain bolt. In fact, most of the stripped oil drain bolts I've seen are from dealerships, so apparently the torque wrench doesn't help that much.

The times I've seen things get stripped, it's from cross-threading the drain bolt and a torque wrench doesn't solve that.

A torque wrench is overkill for a drain bolt. To call it the "most important thing" is just laughable.

ZV

You must have shit dealers in your area, however I wouldn't put it past them as it took them over a month to finally diagnose my alternator as being defective after repeated insistence that it had a bad diode... (Warranty claim)

A torque wrench isn't "overkill" for anything. It would be careless to use a torque wrench to UNdo bolts but certainly not for tightening!

Let me guess, you don't use a torque wrench for spark plugs either I take it?

 

[Muse]

It's a drain bolt. You tighten it until it's snug and stop. If you don't have enough feel to avoid stripping out a bolt, you shouldn't be working with tools at all.

The bolts strip out when people get obsessed with torque specs and crank down hard on the bolt. All the OP needs is a basic box-end wrench and to know enough not to crank down on the bolt. It's not rocket science.

Torque wrenches are for things like head bolts, internal engine bolts, and suspension bolts. If you need one for an oil drain plug, you don't have any business working on a car.

ZV

Actually, what I did was use a box end wrench and got it semi-tight, then tried to crank it a bit more and the pain I felt told me, "hey, that's tight enough!" I have pretty good arm strength, but what stops me is my joints... elbows, wrists and hands. I stopped there (i.e. it didn't get any tighter, but trying to get it tighter hurt!). If it's loose in a year, well, I'll learn something. If it leaks significant oil, I should notice that in my driveway.

 

[Muse]

There is absolutely no such thing as a good "leak stop" product. Sealants in a can are horrible ideas.

Think about it this way, a "sealant" just tries to plug up any hole it finds. It doesn't know which ones are leaks and which ones are necessary parts of the A/C system (e.g. the orifice tube or expansion valve, or the compressor). So what you end up doing with a "sealant" is clogging everything.

The refrigerant/oil mixes are also iffy. A/C systems have a specified amount of oil that they are supposed to have. Too much can be bad just like not enough can be bad. With a can of refrigerant/oil mix you are basically guessing at how much oil you're adding and you have no good way of knowing how much oil is already in the system. It's just not the right way to do things.

ZV

I called a Yelp-reputable shop and they said they don't do A/C. They gave me the number of the shop they recommend "without reservation." I called them, made an appointment and also called my dealership, who also have really high Yelp ratings, even higher. But the dealership service manager never returned my call, so I took the car to the other place last week. They tested and said the system held pressure. With my permission, they did a diagnosis (~$197 including tax), i.e. added R134a + dye, I came back 6 days later (today) and they looked for leaks using UV light. The guy (he and the other techs in the shop are all A/C certified) calls me and says he detected leaks on the condenser, one main leak and two "pinhole" leaks. He says I'm looking at a total charge P&L of $567. I told him I figured I'd see how fast the A/C becomes noticeably weaker and then make my decision.

I went back to pick up the car and had another conversation with him. I asked if it is feasible for me to do it myself, he thinks so, says it would take me 1 1/2 hours of work. I'd have to let the refrigerant escape into the atmosphere (they get it back in their tank when they do this), replace the condenser (a ~$339 part), recharge and add 2 ounces of "PAG," which is oil.

 

[Zenmervolt]

I went back to pick up the car and had another conversation with him. I asked if it is feasible for me to do it myself, he thinks so, says it would take me 1 1/2 hours of work. I'd have to let the refrigerant escape into the atmosphere (they get it back in their tank when they do this), replace the condenser (a ~$339 part), recharge and add 2 ounces of "PAG," which is oil.

It is not legal in the US to vent refrigerant from an automotive A/C system to atmosphere. Federal law requires that the refrigerant be captured. Do millions of people vent it to atmosphere without getting caught? Yes. But it's a $10,000 fine and, as one of my old law professors was fond of pointing out, any plan that relies on "we probably won't get caught" is a bad plan.

In addition, after installing the new condenser you would need to pull a vacuum on the system for a half-hour to pull out any moisture that may have gotten into the lines when you opened it up to replace the condenser, then let it sit at a vacuum (without the pump running) for another 15-30 minutes to make sure that it's not leaking.

ZV

 

[Muse]

It is not legal in the US to vent refrigerant from an automotive A/C system to atmosphere. Federal law requires that the refrigerant be captured. Do millions of people vent it to atmosphere without getting caught? Yes. But it's a $10,000 fine and, as one of my old law professors was fond of pointing out, any plan that relies on "we probably won't get caught" is a bad plan.

In addition, after installing the new condenser you would need to pull a vacuum on the system for a half-hour to pull out any moisture that may have gotten into the lines when you opened it up to replace the condenser, then let it sit at a vacuum (without the pump running) for another 15-30 minutes to make sure that it's not leaking.

ZV

Thanks, well maybe I'll just have them do it now. Seems like doing it myself is problematical, not to mention illegal. Plus, I figure if I wait, their offer to replace refrigerant free won't apply, since there won't be much left in there when it's clear the system isn't working well anymore.

Thanks... Do you agree?

 

[Zenmervolt]

Thanks, well maybe I'll just have them do it now. Seems like doing it myself is problematical, not to mention illegal. Plus, I figure if I wait, their offer to replace refrigerant free won't apply, since there won't be much left in there when it's clear the system isn't working well anymore.

Thanks... Do you agree?

At the very least, I'd have a professional shop recover the refrigerant if you decide to do it yourself.

It's not that complex, but pulling a vacuum is necessary to get any moisture out of the system that may have gotten in while the lines were open. Moisture from the air will mix with the refrigerant and create a bit of acidity, which will slowly eat the system from inside. It's not catastrophic, but it will limit the life expectancy of the system.

Personally, since I like wrenching, I'd probably do it myself after having a shop evacuate the system. But I've got tools and a set of manifold gauges and a vacuum pump. My recommendation for most people would be to have the shop do it; given the price of the condenser their total quote doesn't seem bad.

ZV

 

[Muse]

At the very least, I'd have a professional shop recover the refrigerant if you decide to do it yourself.

It's not that complex, but pulling a vacuum is necessary to get any moisture out of the system that may have gotten in while the lines were open. Moisture from the air will mix with the refrigerant and create a bit of acidity, which will slowly eat the system from inside. It's not catastrophic, but it will limit the life expectancy of the system.

Personally, since I like wrenching, I'd probably do it myself after having a shop evacuate the system. But I've got tools and a set of manifold gauges and a vacuum pump. My recommendation for most people would be to have the shop do it; given the price of the condenser their total quote doesn't seem bad.

ZV

I figured this inasmuch as I don't have the equipment to suck out the moisture, and realized that their quote doesn't look bad, and made appointment to bring in the car for the work this morning at 7AM. Thanks, ZV, for the info, it's been very helpful! :thumbsup:

I'm wondering a couple of things. It's probably redundant and not necessary but I'm going to ask the guy if he's sure there aren't any other leaks. He's a pro, certified, so I suppose he's reasonably sure and checked the O rings, etc.

My other concern seems more legit to me: He's going to have to unhook a lot of stuff to disconnect the old condenser, put in the new one, hook it all up, fill with refrigerant and oil. I'm wondering how they know that there aren't any leaks after doing all this. Do they put in dye, have me come back in a few days and have a look with a UV light shining? That would seem to me to be the only way to know. Or are they so good at this that it isn't necessary? If a few years down the line the A/C seems to be waning I'd have to think they blew it! I'm wondering if they'd charge extra to include dye and have a look a few days later. Maybe this is standard procedure?

 

[BUTCH1]

No, I don't. I've never worked on a car that didn't have an aluminum oil pan. And you'd have to be a ham-handed sub-moron to strip the threads from over-tightening an oil drain bolt. In fact, most of the stripped oil drain bolts I've seen are from dealerships, so apparently the torque wrench doesn't help that much.

The times I've seen things get stripped, it's from cross-threading the drain bolt and a torque wrench doesn't solve that.

A torque wrench is overkill for a drain bolt. To call it the "most important thing" is just laughable.

ZV

Funny you should mention that, when my car came out of warranty I stopped letting the dealer do the changes, the drain bolt was on so tight I had to put the front of the car on stands to gain clearance for a large breaker bar to loosen it, it was around 80-110lbs on it, damm I was pissed!.

 

[desy]

Its an old car I'd exect the AC to wane in a few years anyway, even if everything is sealed up tight today its old and something somewhere will give.
You have to weigh car payments capital cost insurance etc against all the money you save driving an old car + all the extra maintenance to keep it
Lots of cars your age are at the wreckers not cause they don't work anymore but because of all the nickel and dime issues

 

[gw186]

My other concern seems more legit to me: He's going to have to unhook a lot of stuff to disconnect the old condenser, put in the new one, hook it all up, fill with refrigerant and oil. I'm wondering how they know that there aren't any leaks after doing all this. Do they put in dye, have me come back in a few days and have a look with a UV light shining? That would seem to me to be the only way to know. Or are they so good at this that it isn't necessary? If a few years down the line the A/C seems to be waning I'd have to think they blew it! I'm wondering if they'd charge extra to include dye and have a look a few days later. Maybe this is standard procedure?

From my limited knowledge that's one of the things that the vacuum pump is used for. When the system is open you need to get out all the moisture from the air out or it will end up freezing inside the system. They use a vacuum pump and let it sit hooked up for 20 or 30 minutes and if the gauge doesn't move it's considered air tight.

 

[Zenmervolt]

From my limited knowledge that's one of the things that the vacuum pump is used for. When the system is open you need to get out all the moisture from the air out or it will end up freezing inside the system. They use a vacuum pump and let it sit hooked up for 20 or 30 minutes and if the gauge doesn't move it's considered air tight.

This.

That's why after running the pump for 15-30 minutes, you leave the system sit with the pump off for another 15-30 minutes to see if the vacuum leaks down.

Yes, there's a chance that something else will leak, but IMO that chance is greater for a DIY than for a good shop, especially one that specializes in A/C repair.

ZV

 

[Muse]

This.

That's why after running the pump for 15-30 minutes, you leave the system sit with the pump off for another 15-30 minutes to see if the vacuum leaks down.

Yes, there's a chance that something else will leak, but IMO that chance is greater for a DIY than for a good shop, especially one that specializes in A/C repair.

ZV

I don't know that they specialize in A/C repair. They are just called Kraft Auto, Leo Kraft is the owner, I suppose. I think there are 2 other guys and all 3 are A/C certified. They probably do all kinds of stuff routinely, and I think I'm going to ask them for an estimate on a AAA type thorough inspection of the car. I had this done at AAA in ~2002, am not an AAA member now. These guys are closer and AFAIK will do as good or better job as AAA. AAA is sort of a mill. They probably don't have the giant AAA checklist going on, but might be less apt to miss something major. AAA is sort of a mill.

I'm also considering asking them for an estimate of what they'd charge to do the 30,000 mile service on the car. It has barely over 27,000, but the owner's manual, if you interpret it strictly, would have me do that after 24 months or 30,000, IIRC. Well, it's 17 years now. Maybe I should just do it now!!!

I asked this morning when I brought in the car about how they do the A/C job, if there might be more leaks now, how they know there aren't leaks after replacing the condenser. The owner explained what they do. They'll replace O rings when they install the new condenser, that's standard procedure. The dye they put in is in the oil, so it will remain in the system after putting in the new condenser. If I want, I can bring in the car several days after the job and they'll give the system a look-over with the UV light and make sure there aren't any leaks. I have a mind to do that next week.

I'm wondering what screws up the condenser. I watched a Youtube video, almost 4 minutes this morning of a guy replacing the condenser. Why do they get leaks?

I still have the oil sample I collected when I changed out the oil a few weeks ago, May 25. The new and old oil were Mobil 1 Full Synthetic, and the old oil (which I put in a year earlier) was the first change in over 10 years. Would it be worth it to pay the fee and send Blackstone the sample I just took? I'm wondering if it would be a waste of money or would just serve to confuse things. What kind of info might I expect from Blackstone?

 

[Zenmervolt]

I'm wondering what screws up the condenser. I watched a Youtube video, almost 4 minutes this morning of a guy replacing the condenser. Why do they get leaks?

Like anything else metal, they corrode. They're also up in the front of the car and subject to stone and rock impacts, etc. Plus, unlike a radiator which will see perhaps 22 PSI at the most, a condenser will see 150+ PSI of pressure, so that's harder on it too.

I still have the oil sample I collected when I changed out the oil a few weeks ago, May 25. The new and old oil were Mobil 1 Full Synthetic, and the old oil (which I put in a year earlier) was the first change in over 10 years. Would it be worth it to pay the fee and send Blackstone the sample I just took? I'm wondering if it would be a waste of money or would just serve to confuse things. What kind of info might I expect from Blackstone?

I wouldn't send in the 10-year-old oil. It won't really tell you anything useful on its own and will probably just cause needless worry.

For the one-year-old oil that you just replaced, yes, I'd send in that sample. Get a TBN done as well and if that shows good, they may be able to tell you that it's OK to go for two years on the new oil.

ZV

 

[bryanl]

I called a Yelp-reputable shop and they said they don't do A/C. They gave me the number of the shop they recommend "without reservation." I called them, made an appointment and also called my dealership, who also have really high Yelp ratings, even higher. But the dealership service manager never returned my call, so I took the car to the other place last week. They tested and said the system held pressure. With my permission, they did a diagnosis (~$197 including tax), i.e. added R134a + dye, I came back 6 days later (today) and they looked for leaks using UV light. The guy (he and the other techs in the shop are all A/C certified) calls me and says he detected leaks on the condenser, one main leak and two "pinhole" leaks. He says I'm looking at a total charge P&L of $567. I told him I figured I'd see how fast the A/C becomes noticeably weaker and then make my decision.

I went back to pick up the car and had another conversation with him. I asked if it is feasible for me to do it myself, he thinks so, says it would take me 1 1/2 hours of work. I'd have to let the refrigerant escape into the atmosphere (they get it back in their tank when they do this), replace the condenser (a ~$339 part), recharge and add 2 ounces of "PAG," which is oil.

Is that $567 plus the $197 diagnostic fee, or does it include everything? A diagnosis shouldn't cost more than one hour of labor plus the leak detection dye.

R-134a isn't just as bad for the environment as R-12 but damages the ozone layer far less (zero) and has only half the global warming potential. It's also disturbing that the first mechanic recommended an A/C sealant (risky) and said synthetic oil shouldn't be used in the engine of your car because Mazda warns against that only for their rotary engines. Their piston engines work perfectly fine with synthetic, whether it's made of synthesized molecules or is just ultra refined dino oil. Also using a quart of conventional oil in place of synthetic won't help prevent leaks, and if any seals are marginal, leaks will be prevented only by using a quart or less of synthetic.

If you operate the A/C in mild weather with the fan set to low, the compressor may not run enough. Instead use a faster fan speed to make the compressor run more, and avoid a chill by setting the temperature higher.

 

[Muse]

Is that $567 plus the $197 diagnostic fee, or does it include everything? A diagnosis shouldn't cost more than one hour of labor plus the leak detection dye.

The $567 was a separate charge. The diagnosis included $6 for dye, $37.20 for R134a, $150 labor, $3.89 tax.

The $567 (that was the quote, it actually came out to $565.93), included $348 for the compresser, $6 for the PAG oil, $180 labor, $31.87 tax. Presumably the recovered R134a was up to spec for the recharge.

I got a quote from the owner on the 30,000 service. It includes spark plug replacement, inspecting a ton of items, lubricating hinges and locks. The car has 27,000 miles on it, but at 17 years old it's way overdue for that service. I changed the oil and filter and the air filter over the last few weeks myself, so they won't have to change those items. He said it would come to around $120 in that case. I asked him if they could check out the driver's side door lock -- in cooler weather (and a lot of times in warmer weather), the button doesn't pop up high enough so the door can be opened by the handle. He said if they had to remove the door panel it would be a slight additional charge. Looking at that now, I'm convinced it has something to do with the button not being able to pop up as high on that door as the others. It's by I'd say 3/16 inch. I'm going to call them sometime this coming week and schedule to bring in the car for the service. I asked the owner if they could have a look with UV and make sure there are no leaks at this time in the A/C system. They told me that the dye is in the oil and that it's still in there.

R-134a isn't just as bad for the environment as R-12 but damages the ozone layer far less (zero) and has only half the global warming potential. It's also disturbing that the first mechanic recommended an A/C sealant (risky) and said synthetic oil shouldn't be used in the engine of your car because Mazda warns against that only for their rotary engines. Their piston engines work perfectly fine with synthetic, whether it's made of synthesized molecules or is just ultra refined dino oil. Also using a quart of conventional oil in place of synthetic won't help prevent leaks, and if any seals are marginal, leaks will be prevented only by using a quart or less of synthetic.

That first mechanic was a guy I played with on the golf course a couple of times, he was a mechanic for 17 years, now works at a local oil refinery. He told me he has 5 cars! I took his advice with a grain of salt, and as you point out, that salt was crucial.

If you operate the A/C in mild weather with the fan set to low, the compressor may not run enough. Instead use a faster fan speed to make the compressor run more, and avoid a chill by setting the temperature higher.

Does the temperature even have to be in the cooling range? The temperature guage on this car ranges all the way from very cold to in-the-middle to very warm. To get the compressor to run enough, can the temperature be set to middle (i.e. no effect), or even warm? Is the crucial thing just the fan speed?

 

[Zenmervolt]

If you operate the A/C in mild weather with the fan set to low, the compressor may not run enough. Instead use a faster fan speed to make the compressor run more, and avoid a chill by setting the temperature higher.

The A/C in a 1997 Mazda 626 uses an expansion valve instead of a fixed orifice tube. This means that the compressor does not cycle; it runs continuously. It's only the orifice tube systems that cycle the compressor in normal operation.

Does the temperature even have to be in the cooling range? The temperature guage on this car ranges all the way from very cold to in-the-middle to very warm. To get the compressor to run enough, can the temperature be set to middle (i.e. no effect), or even warm? Is the crucial thing just the fan speed?

In your case, you don't need to worry about it for the reason I've outlined above.

That said, the temperature selection only affects how the air is blended after it has gone through the A/C system. The A/C always tries to make the air as cold as possible; changing the temperature selection adjusts how much warm air is mixed with the A/C's cold air, but it doesn't change the temperature of the air coming out of the evaporator. What this means is that if you have the A/C switched on and select the hottest selection possible, the A/C is still making cold air, it's just that the air is then mixed with hot air from the heater core which overpowers it and you get warm air from the vents.

ZV

 

[tortillasoup]

The A/C in a 1997 Mazda 626 uses an expansion valve instead of a fixed orifice tube. This means that the compressor does not cycle; it runs continuously. It's only the orifice tube systems that cycle the compressor in normal operation.

That's interesting, do you think they did that to save fuel? Though the idea of the compressor never shutting off seems a little odd as room air conditioners will cycle on and off even if they're equipped with a TXV.

 

[Zenmervolt]

That's interesting, do you think they did that to save fuel? Though the idea of the compressor never shutting off seems a little odd as room air conditioners will cycle on and off even if they're equipped with a TXV.

Well, they'll cycle on and off if they over-pressure on the high side or under-pressure on the low side, but not at anything like the rate that orifice tube systems do (which can be several times a minute). Since an orifice tube has a fixed-size hole, the only way to regulate flow is by cycling the compressor. An expansion valve can vary the size of the its opening and does not require nearly as much cycling of the compressor to regulate refrigerant flow. Typically the systems I've seen with expansion valves will cycle on hot days when the car is sitting still and air flow over the condenser is lowest, but, again, not at the rate that orifice tube systems will cycle.

Most European and Japanese cars I've worked on use expansion valves, while most of the Fords and Chevrolets I've seen use the simpler orifice tube systems, though more recent domestics also seem to be moving towards systems with expansion valves for efficiency reasons.

ZV

 

[Muse]

The A/C in a 1997 Mazda 626 uses an expansion valve instead of a fixed orifice tube. This means that the compressor does not cycle; it runs continuously. It's only the orifice tube systems that cycle the compressor in normal operation.



In your case, you don't need to worry about it for the reason I've outlined above.

That said, the temperature selection only affects how the air is blended after it has gone through the A/C system. The A/C always tries to make the air as cold as possible; changing the temperature selection adjusts how much warm air is mixed with the A/C's cold air, but it doesn't change the temperature of the air coming out of the evaporator. What this means is that if you have the A/C switched on and select the hottest selection possible, the A/C is still making cold air, it's just that the air is then mixed with hot air from the heater core which overpowers it and you get warm air from the vents.

ZV

So this means the compressor runs all the time? Or just when the A/C is on? The shop owner told me that I could get the oil circulated during cooler weather by running the defroster, not mess with the A/C.

So, it's either run A/C (with any temp setting), or run the defroster to circulate the oil?