I had the alt tested tonight, outside the car, by 2 different parts stores.
The first place said it was fine. It was putting out 14.8 volts, steady. diodes
OK, regulator OK, stator OK. (Actually the first guy who was testing it declared it to be bad, only putting out 2 volts, but luckily someoone else came along and helped him out ! ) So I left this place thinking the alt was fine, and headed over to place 2 for a verification.

But at the second place, the readings were inconsistent. The first reading was
13.0, the next, after shutting down the machine, and restarting, was 15.8, the
third was 13.8. Also, the needle wavered slightly at each reading, smoothly
moving up and down very silghtly, about 0.1 volt up and down. But the diodes,
stator and voltage reg were OK.

Another interesting thing about the testing was that neither store had the same
connector as I have in my car. My car has a connector with holes for 4 pins,
but has only 3 pins, all right next to each other. The first parts store had a connector with 4 holes and only 3 pins also, but the pins were not in the same holes as mine ! They insisted their connector was the "right" one, and we went on tetsing with it.
The second store's connector had all 4 pins, and they said that was the only
"right" connector for my car, and they didn't know why I had only 3 pins in
mine. Perhaps it doesn't matter.

The second parts store was trying to get me to buy a new alt, but I pointed out
that their own manual said 13 to 16 volts was the normal range for my alt, and
they backed off.

What about those inconsistent readings at the second store , and the slightly wavering needle ?

btw I am getting a code 53 in the computer, which is 'system overvoltage at
battery' and also 'voltage reference error' and also 'high voltage at egr' and
also 'vats' (anti-theft system).


All comments and suggestions more than welcome !!



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88 GTA 5.7 TPI Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

Were the machines able to put a load on it?

My alternator went bad, but only when it got hot. I had mine tested at Canadian Tire, and it looked fine. I got it tested at a real auto electronics shop, and it wasn't able to put out more than a couple amps after a few minutes.

 

Good question. I think they said there was no load drawn by the machine.

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88 GTA 5.7 TPI Charcoal Grey Bone Stock except for loose muffler which makes it a bit louder than normal.

 

Have you ever heard the saying A man with one watch always knows what time it is, a man with two never does.?

You've got so much information from so many people that I don't think anyone will be able to give you a definite answer. Many problems are often caused by "operator error" - of which I am as guilty of as the next person.

Can you have it tested (again!) by a NAPA store? Of all the parts stores, I feel more confident with them. They seem to be more knowledgeable, at least in my experience.

That first store initially said you had only 2 volts output and the other giving you several output voltages or saying it was out of "spec" would be "red flags" telling you to take it to a professional place. Maybe it'd be worth trying a starter/alternator shop that specializes in alternators, even if they charge you a reasonable amount to test it.

Based on the codes, it certainly sounds like the alternator is putting out too many volts. This is why I think it's important to have the alternator tested. A poor connection to the alternator and/or battery could also cause an overvoltage to occur. For example, if the voltage sense wire, at least on a CS-130 type alternator (which I think you have), has a poor connection, that could cause the alternator to output too much voltage. Plus, the problem could be intermittant, which is the hardest type of problem to diagnose. I'd be checking for good (tight and clean) connections to the alternator and battery if the alternator checks out okay.

The pins on a CS130 alternator connector are as follows. On mine ('91 V8 VIN F), there are four pins, only two of which are connected to wires.

One of the pins is larger than the rest. This is the "sense" pin (terminal "S") which connects to a red wire (connected to the battery via the starter solenoid stud). This tells the alternator the battery voltage so it knows how many volts to output. This wire is thicker than the next. This is the wire I'd be checking for a good clean connection (at the starter solenoid stud?).

The next wire is a brown wire (terminal "F") that turns the alternator on and off. It will have +12 with the engine running. Power comes from the FAN FUSE.

The next two (closest to the passenger side) pins are not connected to anything. One (terminal "L") would be connected to a light bulb (the idiot light), the other side of the bulb to +12 at the ignition. The fourth (terminal "P") I believe is for a tachometer input. This is connected to the stator, so this pin will have an AC signal on it, the frequency dependent upon the speed of the rotor.

As I said, the only two you'll need are the voltage sense and alternator "on" pins connected.

Sorry I couldn't answer your post.

[This message has been edited by Stuart Moss (edited July 25, 2001).]

 

As a previous Store Manager for Checkers, I know how the machine works. First, go to a place that uses the "Bear" machine. Its a computer that will load test your alt while in the car. It will also make you test it at idle, and at around 2500 rpm (load). I feel this is the most accurate.

P.S. I too have strange problems with my alt. Once in a blue moon, my volts spike up to over 18! I've blown the computer once already by this. Replaced the computer and alt, and once in a while it still spikes. I think they are just bad regulators that are built into these reman alternators.

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Rob
'86 TA 305 TPI
Gutted MAF, Ported Plenum
TB Bypass, Home made Cold Air Intake,
Edelbrock T.E.S.