Easy mod..."turbocharge" your car's AC system.

[Bluefront]

Disclaimer: Try this at your own risk. If you're afraid of splicing wires, if you know nothing about electrical systems in cars, stop reading.

My little ricer car has a manual ac/heater system...this is what I'm talking about. If your car has an auto/ac system this little modification probably won't work correctly. Being the generous person I am, I give you ATOTers the opportunity to "Turbocharge" your car's ac system. My system went from 40/42f at the center vent, down to 28/30f at the center vent with this one mod. Note this will not fix a leaky, worn-out system...it is meant to lower the output temps maybe 10f on a factory stock system.

Most manual ac systems (that I know about anyway) have a set temp that the sysyem tries to maintain. I my case it was 40/42f (center vent). No matter where you set the fan speed, the compressor will shut off once the temp gets that low..turns on as the temp raises. This temperature is maintained by a little electrical unit called a thermister. It has a temp probe that goes into the cooling unit (evaporator). What I did was bypass the thermistor with a simple on/off switch.

My thermistor (underneath the cooling unit) has three wires. #1 is 12v from the battery when the ign is on. #2 is a ground signal from the ECU when you hit the ac switch. #3 is a ground signal from the thermistor back to the ECU, which then sends a signal to the ac compressor, through a hi/low pressure switch. The #3 ground signal is turned on/off by the temp probe. My little trick here is to bypass this on/off signal by splicing into the #3 wire, and sending that signal straight to ground through a simple on/off switch from Radio Shack..

When you flip this "AC Turbo" switch, the compressor stays on all the time, making your AC system as cold as possible. In my case the temps drop dramatically. Colder than it's ever been.

You'll only need to do this in really warm temps, otherwise you could freeze up your system...doesn't really hurt anything though. If you notice white "smoke" from the vents, you're getting too cold. Turn off the turbo switch, or turn off the recirculation switch.

I've been doing this the last three days....Monday was 100 f here. My center vent temp sat at 29f. I cannot see any problems with this setup....as long as you know what you're doing with the "turbo" switch.

Again try it at your own risk....it does require that one splice that goes to the ECU...be careful, double-check the wires before you try anything. Works for me...

 

[pyonir]

how much horsepower will it add?

 

[OS]

cooool, it's like a naaawwwwwzzzz switch for the A/C.

 

[Amused]

That's all fine and good until you freeze up your chilled coils on a humid day. That setting is there for a reason. Doing what you're doing will turn your coils into an ice block if you leave it running for a long trip.

 

[Fritzo]

Yes, it will. Especially if it's humid. All you need is for the fan to freeze and burn out, then you're screwed.

 

[Evadman]

Originally posted by: AmusedOne
That's all fine and good until you freeze up your chilled coils on a humid day. That setting is there for a reason. Doing what you're doing will turn your coils into an ice block if you leave it running for a long trip.

Correct. The temp is usually maintained a few degrees above freezing to prevent this. You bypassed that. Get a larger evaperator core if you are having problems.

 

[Rallispec]

i wonder how that effects performance and gas mileage

 

[Bluefront]

Some of the replies I'm seeing here miss the point......which is the thermostat of this ac system is fixed, cannot be adjusted. In my case the vent temps were about 42f....too warm for my tastes. I get around this set point with a small wiring change (read cheap). Now my vent temps are about 29f...much better.

Buy a bigger evaporator? Get real...first they are not available for this car. Second If available would no doubt cost $400 or more plus installation.

Read what I wrote in the first post.....Flipping the switch to turbo is only necessary if it's really hot out. If it's 100+ outside, bright sunlight, you're in slow moving traffic, there is no reason for your compressor to ever turn off.......it just won't freeze up in those conditions.

Consider this like over-clocking a computer....you're getting a performance increase for almost nothing. And since you're sitting right in front of the vents, you will immediately see the signs of freezing up. White smoke from the vents, lower air volume, etc. In that case you simply turn off the turbo switch.

Like I said...this mod is not for everybody, but it works. Who cares about gas mileage when you're sweating to death. Of course it cuts performance when the ac compressor is running, when your power steering is running, when you crank up that 400w stereo, even when you turn on your headlites. Anything that makes the engine work harder, anything that increases electrical loads lowers your 1/4 mile ET. Me..I want cooler temperatures in the summer.

Now if you really wanted to get fancy, you could install an adjustable thermostadt for your ac....most older AC systems in automobiles had just such a knob somewhere to lower the temps. Wouldn't be very hard at all.....I might do that to my setup.

 

[Nefrodite]

heh too bad they don't have mod shops i'm too lazy to do it myself

 

[Amused]

Originally posted by: Bluefront
Read what I wrote in the first post.....Flipping the switch to turbo is only necessary if it's really hot out. If it's 100+ outside, bright sunlight, you're in slow moving traffic, there is no reason for your compressor to ever turn off.......it just won't freeze up in those conditions.

Sorry, but you're just plain wrong. The air temp at the vents is irrelevant. The air temps in your car is irrelevant. It's the air temps at the coil itself that is relevant. The thermostat is set at the point just above what the engineers found the coils to freeze at.

I did AC work for a few years in So Cal. I've seen freezing coils in 100+ degree weather, and the temp in the house was just as hot, if not hotter. Hell, I had an old window unit do this to me once when I was growing up in SoCal. It was well over 100 degrees when it happened.

Once the ice starts to form, less air is driven over the coils, causing it trap even more moisture and freeze up even more. By not allowing your unit to cycle off, you are just begging for this to happen.

Do what you want, but don't say no one warned you.

By the way, white "smoke" coming out of the vents is not a sign that your coils are about to freeze. When I lived on Hilton Head Island in SC all the cars did this for most of the summer. All this vapor means is that the moisture is condensing between the coils and the vents, and there is too much moisture for the coils to remove. It happens all the time in very humid climates.

 

[Kadarin]

I wonder if you would gain horsepower if you output cold air from the compressor, after making this modification, to the engine intake. Perhaps use it as an intercooler of sorts?

Nah, probably not enough volume.

 

[propellerhead]

I just set the A/C controls in my Ford to MAX? The compressor stays on that way.

 

[hoihtah]

this is most definately an interesting mod.

i'd consider doing this... but the risk factors are too great.

perhaps... when the weather gets real hot... i'll try it.

 

[Amused]

Originally posted by: propellerhead
I just set the A/C controls in my Ford to MAX? The compressor stays on that way.

The "MAX" setting on GM and Ford vehicles simply recirculates the air, rather than pulling fresh air in.

 

[Bluefront]

I think AmusedOne is right about that last one, but he's somewhat off on his other posts.

In the case of my car, I could get the same model with manual or Auto AC. Most of the parts of the two systems were the same...same compressor, same condenser, same evaporator, etc. The main difference is in the controls. My manual AC has one input...the temperature in the cooling unit, as measured by the thermister ( it's also called thermo control amplifier). With an Auto AC, the cooling sysytem has multiple inputs....outside temp, sun-load, multiple interior temps, cooling unit temp, maybe even road speed. This info is sent to a separate computer...which then determines how the compressor operates. The manual AC has none of those inputs, and cannot react to an extremely high outside temp, or to a bright sunny day.

My little mod lets you, by means of a switch, react yourself to these conditions. It's really hot out, the rear of your car has not cooled off yet, you're sitting still in traffic, whatever.....you need the compressor to stay running, no matter what the thermistor is telling the system. You flip the switch, the compressor stays running....you have given your own input to the system.....very similar to what an Auto-AC would do by itself.

There are many reasons a manufacturer may design a manual AC system to not cool quite so well as an Auto-AC system. Maybe they want the salesman to be able to say "This Auto-AC car cools better". It may have something to do with gas mileage....your AC system doesn't work as well as it can=the car gets better gas mileage.

Anyway you can get better performance out of most of these AC systems....my little mod does it for me. If you know what you're doing, you can beat stock performance by quite a bit.

 

[ElFenix]

Originally posted by: Bluefront
I think AmusedOne is right about that last one, but he's somewhat off on his other posts.

In the case of my car, I could get the same model with manual or Auto AC. Most of the parts of the two systems were the same...same compressor, same condenser, same evaporator, etc. The main difference is in the controls. My manual AC has one input...the temperature in the cooling unit, as measured by the thermister ( it's also called thermo control amplifier). With an Auto AC, the cooling sysytem has multiple inputs....outside temp, sun-load, multiple interior temps, cooling unit temp, maybe even road speed. This info is sent to a separate computer...which then determines how the compressor operates. The manual AC has none of those inputs, and cannot react to an extremely high outside temp, or to a bright sunny day.

My little mod lets you, by means of a switch, react yourself to these conditions. It's really hot out, the rear of your car has not cooled off yet, you're sitting still in traffic, whatever.....you need the compressor to stay running, no matter what the thermistor is telling the system. You flip the switch, the compressor stays running....you have given your own input to the system.....very similar to what an Auto-AC would do by itself.

There are many reasons a manufacturer may design a manual AC system to not cool quite so well as an Auto-AC system. Maybe they want the salesman to be able to say "This Auto-AC car cools better". It may have something to do with gas mileage....your AC system doesn't work as well as it can=the car gets better gas mileage.

Anyway you can get better performance out of most of these AC systems....my little mod does it for me. If you know what you're doing, you can beat stock performance by quite a bit.

you've obviously never been in a place where the coils have frozen. once your coils freeze nothing happens until they thaw. so then you're sitting in the hot traffic with no AC. if the thermostat shuts the compressor off when the coils near freezing already then lowering that temp or bypassing the thermostat is going to freeze the coils. go get a recharge if you want colder AC.

 

[jemcam]

Originally posted by: Bluefront
Disclaimer: Try this at your own risk. If you're afraid of splicing wires, if you know nothing about electrical systems in cars, stop reading.

My little ricer car has a manual ac/heater system...this is what I'm talking about. If your car has an auto/ac system this little modification probably won't work correctly. Being the generous person I am, I give you ATOTers the opportunity to "Turbocharge" your car's ac system. My system went from 40/42f at the center vent, down to 28/30f at the center vent with this one mod. Note this will not fix a leaky, worn-out system...it is meant to lower the output temps maybe 10f on a factory stock system.

Most manual ac systems (that I know about anyway) have a set temp that the sysyem tries to maintain. I my case it was 40/42f (center vent). No matter where you set the fan speed, the compressor will shut off once the temp gets that low..turns on as the temp raises. This temperature is maintained by a little electrical unit called a thermister. It has a temp probe that goes into the cooling unit (evaporator). What I did was bypass the thermistor with a simple on/off switch.

My thermistor (underneath the cooling unit) has three wires. #1 is 12v from the battery when the ign is on. #2 is a ground signal from the ECU when you hit the ac switch. #3 is a ground signal from the thermistor back to the ECU, which then sends a signal to the ac compressor, through a hi/low pressure switch. The #3 ground signal is turned on/off by the temp probe. My little trick here is to bypass this on/off signal by splicing into the #3 wire, and sending that signal straight to ground through a simple on/off switch from Radio Shack..

When you flip this "AC Turbo" switch, the compressor stays on all the time, making your AC system as cold as possible. In my case the temps drop dramatically. Colder than it's ever been.

You'll only need to do this in really warm temps, otherwise you could freeze up your system...doesn't really hurt anything though. If you notice white "smoke" from the vents, you're getting too cold. Turn off the turbo switch, or turn off the recirculation switch.

I've been doing this the last three days....Monday was 100 f here. My center vent temp sat at 29f. I cannot see any problems with this setup....as long as you know what you're doing with the "turbo" switch.

Again try it at your own risk....it does require that one splice that goes to the ECU...be careful, double-check the wires before you try anything. Works for me...

If you live in a humid area, your evaporator core will turn into a solid block of ice in a pretty short time. Then your a/c will blow warm. This is the reason the compressor cycles, to keep it from getting too cold and freezing up. a/c's work by removing moisture from the air more than anything. That's why your a/c drips when it's on.

 

[Bluefront]

He,he,he. Let's see..you want it cooler, add more freon. Yeah right.

My system works with 1.5lbs of 134a freon. Add more your cooling will go down, same with less. Anyone who thinks he cannot make a system like mine perform better....stop reading this thread.

Look...you guys need to think...if you notice the system getting warmer, maybe it is icing up. Turn off the switch....any ice in the evaporator will melt quickly. My own system will not ice up at temps over 100f, in bright suunlight. Obviously every car will react differently to this mod. Since it costs nothing, if you're talented enough with your car tools and you want a colder AC...try it.

 

[Howard]

R-134a is not freon.

 

[KMurphy]

Someone is dense. The thermostat is set to trip the compressor just before the coils freeze up. Bypassing that will screw your AC system in short time. Why would you want to manually cycle your compressor while driving? That's like pissing into the wind.

 

[C'DaleRider]

Someone is dense.

True. Either that or he knows everything about everything and talking facts to him is pointless. Sounds like the true Immovable Object.

 

[Linux23]

Originally posted by: KMurphy
Someone is dense. The thermostat is set to trip the compressor just before the coils freeze up. Bypassing that will screw your AC system in short time. Why would you want to manually cycle your compressor while driving? That's like pissing into the wind.

 

[BD2003]

29f? Farenheit I assume? Trying to make ice or something dude?

 

[ThisIsMatt]

I did this...I actually put two buttons on my steering wheel so it looks like I have a two stage nitrous system. The only downside is that when I push the buttons I actually lose horsepower due to the compressor coming on