Dying alternator? -- Fails load test

[Torn Mind]

My mom has a 2007 Toyota Matrix base model. Now, I did try this with a good battery(cranks fine and shows plenty of voltage) and just cleaned the electrical connections today because it couldn't start yesterday. After the engine re-learned its idle, it is still failing the load test when it is warm. When I turn on the headlights, blower motor to max, radio, and rear defogger, it is enough to drops the voltage received at the OBD device to around 12. Turning on high beams and the AC further decreases the voltage to around 11.

At around fast idle, which is when the engine is cold, the car puts out about 14.2 volts.

It's about 50 degrees outside here, if that is any help.

The Matrix doesn't have an adjuster, there is a tensioner that tightens the serpentine belt.

 

[LTC8K6]

12 volts dropping to 11 volts at normal idle is unacceptable.

 

[leper84]

Not sure but I'd imagine parts stores would have a battery tester capable of running a battery/starting/charging test, if you want to be sure.

If its any help the alternators on Toyota 4 cylinders around that year are a common problem. Any noises, discoloration near the alt pulley or burning electrical smell in that area under the hood?

 

[tortillasoup]

If there is a known issue with the Toyota 4 cylinder alternators then just replace the damn thing. Toyota made some bad alternators in the 2000s as I had to replace an alternator in a Tundra that exhibited a similar issue to OP's.

 

[Torn Mind]

Not sure but I'd imagine parts stores would have a battery tester capable of running a battery/starting/charging test, if you want to be sure.

If its any help the alternators on Toyota 4 cylinders around that year are a common problem. Any noises, discoloration near the alt pulley or burning electrical smell in that area under the hood?

Well, there is the problem of whether the store's tester is in commission or if they can find the proper connector. I've had more than enough instances where I go to one and they couldn't test it for those reasons.

When the weather is better and the illness I have clears, I'm probably gonna take off the thing and check the brushes, slip ring resistance, diode, and voltage regulator. I doubt the regulator is the problem since when the load is not too heavy, I do see 13.8-14.2 volts. Diodes might be a minor problem since I see around .03 AC volts, although it spikes up to .1 AC volts. The rotor hasn't shown major symptoms of failure, like audio volume dropping or lights dimming; when the car accelerates, plenty of voltage is produced.

There are no noises or anything out of the ordinary. Just that the voltage is insufficient when headlights, blower motor, AC, and one of the rear defogger or high beam are on.

When the car has the accelerator pedal pushed down, the alternator produces plenty of voltage and the battery hasn't had a bad voltage reading either. The no start condition was due to battery terminal corrosion and the voltage at the battery seems fine at 12.60ish volts.

 

[bryanl]

..

 

[bryanl]

I'd check the alternator belt for slippage all connections at the battery, alternator, and grounds. I had a car known for its battery voltage rising 0.5V by clamping a negative jumper cable from battery to alternator case. Looking at the alternator output with an oscilloscope can quickly reveal a failed diode. Was your Toyota manufactured with a Delco CS130 series alternator?

 

[Torn Mind]

I took the time to crack it open today. Looks like one diode failed OPEN as no amount of lead reversing and metal scratching could get it to register anything while the other three test points passed and are still perfectly functional. This alternator is not bad from a rust bucket standpoint, because while Maryland does get its salt, it's not super frequent like in colder states, so there is still "shine" on the metal even though it has been 9 years.

Also, according to the info provide at workshop-manuals.com, the voltage regulator should be high resistance one way and very low resistance(below 1 Ohm) the other. Well, it does have high resistance one way but lower but still high resistance(around 8 MegaOhms) the other on both test combinations, "F and B" and "E and F".

A "soft failure" of sorts, since the battery voltage is still 12.6 and neither I nor my mom ever tax the electrical system heavily enough to have the battery drained.

Brushes are 5.1 mm and the minimum spec'd by Toyota is 4.5 mm. I suppose it has another 20-50 thousand miles to go on these brushes.

Slip rings seem fine, the lowest ohm reading was 2.8 ohms or so, so the rotor and stator guts are still fine, and the alternator spins will no real resistance.

I'll be posting pics of the meter results too, for informational purposes.

 

[bruceb]

Since you already have it apart, you may as well put in new brushes, regulator and diodes. That should fix it for certain and it will be good for quite some time. Also check the heavy wire from the alternator back to the battery or fuse block and be sure the connections are clean and tight. There is also a slight chance your Serpentine Belt Tensioner is failing and not putting enough pressure on the belt. This would cause the alternator to not charge as well at idle speed. Tensioners are not costly and are usually easy to change (new belt as well, depending on mileage on existing one)

 

[Torn Mind]

Since you already have it apart, you may as well put in new brushes, regulator and diodes. That should fix it for certain and it will be good for quite some time. Also check the heavy wire from the alternator back to the battery or fuse block and be sure the connections are clean and tight. There is also a slight chance your Serpentine Belt Tensioner is failing and not putting enough pressure on the belt. This would cause the alternator to not charge as well at idle speed. Tensioners are not costly and are usually easy to change (new belt as well, depending on mileage on existing one)

It charges at idle fine when there is no load or a lighter load but when I hammer the system with high beams and headlights, rear defroster, and max fan with AC, the output is not enough and the voltage drops. When it is just radio, headlights, and maybe the fan at low speed and A/C, which is how the car is typically driven, the voltages look fine.

I don't have the parts on hand now, so I just put everything back together since this alternator is still working, just not at maximum capacity.

Looks like it will cost $54.50 total on Ebay for an aftermarket regulator, rectifier, and brushes. I'll probably just swap the new one I put on the 1996 Camry onto the Matrix and swap the Matrix's brushes to the Camry as they are interchangable.

 

[Torn Mind]

http://imgur.com/a/4QOKH

This is the Imgur album for some of the testing I did with the multimeter. Since all but one of the diodes checked out good, I didn't take pics of any of the good ones with polarity reversed.

 

[leper84]

Having seen more of a few of those alternators fail, you really should replace the bearings as well.

 

[Torn Mind]

Having seen more of a few of those alternators fail, you really should replace the bearings as well.

I think I'll let this one die if the bearings actually go and buy a reman. Don't have the tools, willingness to spend money on the tools, nor the patience to do a bearing swap. Besides, the rotor or slip rings might already be dead by then, and an alternator with a bricked rotor is as good as scrap metal.

It has lasted 110,000 miles. It probably can last another 50,000-80,000. Still spins good and I didn't hear anything when using a wrench as a makeshift stethoscope.

 

[LTC8K6]

I wouldn't want that AC voltage floating around, though. It may not damage one of the computers, but it would be on my mind.

 

[Torn Mind]

I wouldn't want that AC voltage floating around, though. It may not damage one of the computers, but it would be on my mind.

There's about .02 AC volts registering on my meter. If the two diodes first failed short, it would have been a while ago. Apparently, open diodes do not result in AC voltage going through the system, making them hard to detect.

After coming across autoshop101.com, I now realize that it is two diodes, one negative and one positive, that have failed. They just happen to occur at the same testing point or pathway, leaving the other three diode pairs to do the work.

 

[Torn Mind]

Hmm, interesting. I have a new voltage regulator from having to replace an alternator on a 1996 Camry, which is compatible with the Matrix's voltage regulator. When I place the red lead on the F terminal and the black on the B+ terminal, the new regulator shows about 8.4 MegaOhms and nothing if the leads are reversed.

But on the old Matrix regulator, when red is on F and black on B+, I see about 16 MegaOhms that way. If the leads are reversed, I see about 8 MegaOhms. The regulator still manages to be function properly though, haha.

 

[LTC8K6]

Be sure to check for AC at the back of the alternator under load, and not at the battery posts. IIRC the battery smooths out the ripple.

 

[Torn Mind]

Be sure to check for AC at the back of the alternator under load, and not at the battery posts. IIRC the battery smooths out the ripple.

I already did when trying to find a bad diode without taking anything out. Showed no difference. There probably would be ripple had the diodes failed short rather than open. With open diodes, it seems to be the equivalent of taking something and physically cutting the diode.

At the battery, there would only be a brief spike to .1 AC volts sometimes before it would go back down to .02-.03 AC volts.

 

[sontakke]

Be sure to check for AC at the back of the alternator under load, and not at the battery posts. IIRC the battery smooths out the ripple.

Unless you are suggesting to disconnect the battery while the engine is running, it matters very little where you measure the ripple. Hefty cable is connected from the alternator to the battery post. If you are seeing significant difference at the two end of that cable, you have bigger problems.