GlenL

That alternator will mount correctly but won't accept the vent duct on the rear.

Landseer

If money is an issue, buy a rebuilt 105 Amp alternator for an 88 Camaro, a pigtail and the next shorter belt at your cheapest parts store and do what is known here as the Delco converstion. Particularly simple on all pre-85 cars and effective. Can be had for $80 or less.

I run Bosch originals on the 85 & 6, and on the 944. Delco on the 84 cars.

LP928

I found a shop thats not to far away I was planning on taking it there to be rebuilt, but I may try to do the voltage regulator now.

LP928

Ok, I took my alternator to an ignition shop - Lorida Ignition and had it tested. The guy tested it and found out that a diode or two were bad. He replaced all the bad diodes and put in new brushes. Then gave it back and said it was good. I installed it on my car and started it up, at first it seemed ok, I got 13.3 or so volts at idle, when there were rpms though my multimeter read crazy, jumping around at 2,3,4 etc. I might not of had a good connection with the multimeter. The charge light in the dash still wouldn't light up during the light check. Later I started my car again and read the volts of the multimeter, It only read 12.1 through all the rpms. It stayed like that for the rest of the day. I then cleaned the 14 pin connector at the passenger wheelwell and put in some di electric grease. I also took the alternator off, not disconnected though, with the back cover off I then took voltage readings as shown:

Ign. OFF:

battery + - Exc. = 12.4V
Exc. - Ground = .26V
Battery + - Ground = 12.7V


Ign. ON ( not motor):

Battery + - Ground = 12.4V
Battery + - Exc. = 11.5V
Exc. - Ground = .64V

Any ideas why my alt is not charging much?

I did have the dash apart last week


Thanks

Kyle

Alan

Well I'd say the obvious answer is your exciter circuit is broken.

Stop measuring things between circuits e.g. battery and exciter etc its pretty meaningless - all measurements should be just w.r.t. a good ground - nothing else.

Back again to basics - you have to do it... I feel a bit like I'm banging my head against a wall... if you need help and get good suggestions maybe you should just do them before asking the same questions again...

Remove the exciter wire from the Alt. With the ignition on what voltage do you get? It should be battery voltage. If not you have no connectivity in the circuit - backtrack as needed to find the problem area (14 pin connector->CE panel->Pod - see diagrams) if you do have battery voltage - ground the exciter wire - does the dash (no) charge light come on? If no you similarly have a high impedance connection problem in the circuit or the bulb is burned out (most uncommon).

Since you say you have been in the pod recently you probably disturbed some connections there that affected the voltmeter and exciter - thats where I'd expect to find the answer...

Alan

LP928

The alternators getting battery voltage no problem. When the exciter wire is grounded the no charge light does not come on. I pulled the dash pod forward and tried pushing the connectors together however they are in pretty bad shape, falling apart, I might need to work on those more. I also checked the bulb and it is fine. So i could not get the no charge light to come on.

I wasn't sure whether you meant alternator voltage or exciter wire voltage so I tried both, only the alternator had battery voltage.

Sorry for my ignorance but I have never worked on car electronics before and this is all new.

WallyP

There are two connections on the alternator.

The large terminal is the alternator output, and is always hooked directly to the battery positive terminal. You should always have at least battery voltage (measured to ground) on this terminal. If the engine is running, and the alternator is functioning, you should have 13.6 - 14.4 volts to ground.

The small terminal is the exciter circuit. The alternator must have voltage on this terminal to begin generating power. This voltage starts at the battery, flows thru the ignition switch to the warning light bulb and a resistor mounted in parallel to it on the back of the voltmeter. From there, the power flows thru the Central Electric Panel to the 14-pin connector near the jump start terminal, and from there to the small connector on the back of the alternator. From there the power flows thru the brushes to the armature (the rotating part) where it creates the magnetic field that is drug thru the field coils, generating the charging current.

An alternator converts rotary energy into electrical energy by moving a magnetic field (the armature) thru the coils in the housing. The magnetic field MUST be present for the alternator to generate electricity. It is initially created by the excitation current that is supplied thru the charging warning light and the parallel resistor (mounted on the back of the voltage gauge). If the excitation current is too weak (bad resistor, bad bulb, bad connection), but present, the alternator will start charging ONLY at higher RPM levels. If the excitation current is not present at all, the alternator will never charge (unless there is sufficient residual magnetism left in the rotor to start generation).

Once the alternator starts charging, it supplies its own field current. Since there is now voltage on both sides of the light/resistor combo, the light goes off. Once the alternator starts charging, the light/resistor combo has no effect.

If the charging warning light is on, there is voltage on one side of the bulb and not the other, and there is a problem, usually in the alternator.

The alternator coils produce AC voltage, which is not useful for our purposes. The alternator includes six charging diodes (one-way check valves for electricity) that convert the AC voltage to slightly-pulsing DC voltage. If one diode is failed open, the charging amperage will be reduced. If one diode is failed shorted, there will be AC ripple in the output voltage, and you will get whine in the radio. As more diodes fail, the conditions will worsen.

Landseer

Great description, Wally!

Exciter wire path runs from alternator (little wire)
to #1 terminal @ 14 pin.

to CE panel plug indentified as plug O, terminal 8

LP, you sound like a skilled first-time 928'r, good troublshooting attempts so far. Keep up the good work. Don't hesitate to get help from Firemed, as above he offered to help you and is extremely knowledgeable.

Can you say more about the plug problems in the dashboard? Those connections are important and that printed circuit board needs to be carefully cleaned and connections made.

Pictures help on any such troubleshooting. You might need to join the Rennlist group for $17 / yr, paypal, so you can see the pictures that we post-up of various problems. ( Not sure if you can post pictures directly without that membership, or just not see ours.) T

Sounds like your alternator repair was successful, it might even self-excite without the exciter circuit, but it would be better to get this straightened out.

LP928

Thanks for the detailed descriptions that helped a lot, I've been meaning to become a member I'll see if I can do it today. I can see pictures however and have posted pictures in the past. The plastic connectors in the dash board have all broken off their mounts and no longer "click" together basically every time I take the dash apart I have to re thread the plastic tab with all the contacts on it into the broken off clip, slide the plastic rectangle inside, then cram the other connecter onto it, and hope it doesn't fall apart . Is there any way to replace the plastic connectors or would I have to replace the whole instr. cluster circuit board? Also when I cleaned the 14 pin connector by the passenger fender, one off the wires insulation had desinengrated , it was the brownish one that merged with the yellow wire in one of the corners. I cleaned all contacts put in some di electric grease and taped the falling apart wire. I will try to check the ce panel as said in the above posts.

Thanks

Kyle

Landseer

Do you mean the white plastic thin long connectors that attach to the circuit board?

I might have harvested just these from a wreck and could splice them onto harness.

Pics are best here if you can figure it out. Harness problem and 14 pin. Better to solder, but tricky, got to head to work now. Be safe. Remember you have gurus around you down there.

pokegama

LP, I just went through rebuilding my engine harness because the wires going into the 14 pin were crumbling. Upon further investigation by cutting back the harness wrap I could see the wires were fried way down the line...all of them. The insulation on the exciter wire at pin one was almost completly gone and the wire was coroded. Just saying that if you have some crumbling insulation at the plug it most likely goes way deeper than that....worth a look.

IndyMatt

I may be faced with doing this as well since I am havcing some interesting charging problems myself.

Pokegame do have a writeup detailing how you went about rebuilding it?

Alan

Well based on what you have said there is a clear open circuit comewhere between the ignition switch and the alternator on the exciter circuit.

You should probably start with R&R of the known bad pod connectors...

However easy diagnoistic testing would be - ignition on - do you have batt voltage on CE pin O8? if no: focus on the pod connections if yes: focus on the 14 pin connector

Alan

WallyP

"Also when I cleaned the 14 pin connector by the passenger fender, one off the wires insulation had desinengrated , it was the brownish one that merged with the yellow wire in one of the corners."

That is Terminal 14, and all of those wires are actually yellow. One goes to the small terminal on the starter solenoid to trigger the starter, one goes to the cold start valve to trigger it when starting, and the other comes from the starter contacts on the ignition switch thru the Central Electric Panel.

LP928

I will find pin 08 and check for voltage. I was talking to Mike(Firemed) earlier today and he had me jumper the exciter post on the alternator to the charging post with exciter wire off and the alternator charged good. I believe I had two problems with my alt. one was the bad diodes, and the other which still needs to be resolved is the open circuit in the exciter circuit, as Alan has been trying to tell me.