ELECTRICITY, BACK TO BASICS (specifically GM)

[Stewart G. Griffin]

OK, um, this probably isn't the best website to post in (actually maybe it is--read on) but i figured that alot of GM techs lurk on here so maybe you could help. Also, the electrical system of 60 degree engines is very similar if not identical to 2.2 motors.

Anyways,

I got a 2.2 engine in a 90 cavalier. Lately, like yesterday, the voltmeter reads below 12 when i'm driving at night with the headlights on. Consequently, the car would not start today.

After i jumped it, i noticed that it would (seemingly)charge ok at idle (900rpms or so) with a voltmeter reading of about 13.5 (actually is 13.5 ok?) with the headlights turned off. But when i drove it (this is at night so i had to turn on the lights) it would only charge at about 11ish or below 12 let's put it that way. And also, the turn signals were REALLY slow. I would then park it and let it idle and turn the lights off and we get 13.5ish on the voltmeter.

Now, this car has been sitting for about 2 or 3 months and i just started driving it thursday BUT i took the battery out of another car that i was driving during the past two months so i know the battery is good.

The only other thing i've changed since yesterday is that i've cleaned the battery terminals off.

Any suggestions?

2) how do you test these alternators? This has one of those "2 wire hookup" things and no "D" shaped hole so you can't test with a screwdriver or something like that.

[Superdave]

the alternator controlls the chassis voltage while the engine is running, if the voltage is low and if it drops like that when you turn the headlights on it's going out. any good auto parts place can test it but they're just going to tell you the same thing. replace the alternator and you'll be fine.

[sharkey]

well, if you put a different battery in it and its fine now, im gonna say its battery. what many people dont realize is when a battery gets a dead cell in it, or a plate comes loose and shorts, it will cause low voltage problems. if you are driving the car with a good battery and its fine, i wouldnt worry about it. if it starts giving you issues, have the alternator tested.

and 13.5 volts is just fine

[Stewart G. Griffin]

Some Further Clarification(s):

When the car was sitting for the past few months--there was no battery in the car; When i started driving this car again on thursday, i took the battery out of another car. This battery is only two months old and i never had any problems with it in the other car. So, basically i'm betting it is not the battery that is the problem.

OK, anyways, today i just drove with and without the lights on and basically i get 12ish volts without the lights and with the lights on 11.9-8-7-6- maybe dipping to 10.7-8-ish volts. Also, as mentioned before the turn signals and wipers get kinda slow. If i keep driving this way, eventually the car will not start.

Now, when i pull over and just idle, the thing charges around 13.5 and sometimes up to 14.6-7's. If i turn the lights on while i do this i get 13 flat. Of course, when the fan kicks in, the voltage reading goes a little lower. Car starts fine if i let it idle like this before shutting off.

Also, i can turn the alternator by hand a little with the engine off. In very cold weather there is some squeaking but when warmed up there is virtually no squeaking. The alternator is, however, turning at good speed; I have visually checked this.

I, too, am leaning towards the alternator.

But, how can we test it? There appears to be no "F" (field) terminal? I'm sure you probably know what these newer alternators look like, but i can post pictures if nessesary.

[bszopi]

Take it out, bring it into an auto parts store, and they will test it for free. The testers have all the right hook-ups in order to put a load on the alternator and see if it is charging correctly.

[Steevo]

More than likely a one slightly cooked Diode. I did it with my high beams on with AC on max, then I kicked on my subs. Burned up two batteries with that alternator and had problems until I just broke down and had a high output ordered and put in.


The temporary high voltage demand to charge up the caps was too much for one of the diodes in the rectifier and burned it out. After I suffered from about 10V output when I would run with my headlights, A/C or subs on. Now with everything cranked up I never drop below 13V.

[Stewart G. Griffin]

Ok, i found the problem; The belt was/is slipping. I noticed that the power steering was very difficult to steer when the charging went down. When charging go up, easy to steer.

So, anyways, can you tell me everything about belt pulley assemblies? This one doesn't seem to be doing to well or i may have the wrong belt. The pulley tensioner is, if memory serves, an offbrand job---dayco i think, which was replaced only two yrs ago.

[Steevo]

If it isn't squealing (or burning or glazing) the belt, you might want to check for oil or something else on the belt.


I'm sure one of the other masters here can tell you how much deflection the belt should have under a certain amount of weight. That will tell you about how well your tensioner is doing.

[CNCguy]

So, anyways, can you tell me everything about belt pulley assemblies? This one doesn't seem to be doing to well or i may have the wrong belt. The pulley tensioner is, if memory serves, an offbrand job---dayco i think, which was replaced only two yrs ago.

Check for the obvious glazing or contaminations and if you don't see any, check the tension and travel on the tensioner. A belt that is too long will cause the tensioner to run out of travel before the belt is tight. You can check it by marking the tensioner location with the belt on, then remove belt to be sure that it has more travel.

[Stewart G. Griffin]

OK FALSE ALARM:
Thanks everyone for the help. It turns out my belt was too long; i ran a Dayco 5050845 (84.5") for about 16 months. Today i tried the Dayco 5050535 (83.5"). Suprising how much 1" makes! No more squeaking/squawking. The powersteering works great and the alt is keeping the battery charged at at least 14.7volts all the time regardless if i have my lights on or not. The dash lights are bright, windshield wipers and turn signals work at normal speed now.

The tensioner did run out of travel with the old belt and apparently the alt was not turning at normal speed along with the P/S pump.

So, basically i drove around with the wrong belt for 16months. How stupid. At the same token if you go to all the auto parts websites, i.e., NAPA, Autozone, Advance, Checkers etc. They all list Dayco/goodyear/gates 5050845 as the correct belt for A/C 90 cavaliers.

[geoffinbc]

Yea parts listings are usually good but sometimes have mistakes. If you can read the numbers off the old belt to get your replacement. Even the stock belt will have a belt number that will be the same across all brands.