Shawn Stanford

I doubt more than three people have been following my thread, so let me say it here: I've got a new problem.

The other day I was in the relays in the footwell trying to run down the high beams not functioning. I found a DIY wire running from a pin on the starter relay to ground. I pulled it, and everything seemed fine. Car started, no problems.

Yesterday I decided to take the 928 to work and as I pulled out of my alley I noticed the battery light is on and there are only 10 volts in the system. Normally it shows 14v when the car is running. So, it looks like the alternator has quit. This is the brand new alternator the Kary & his neighbor put in last Frenzy.

Since I hadn't touched anything else, I decided to go back to the last known good configuration, which meant reconnecting the jumper on the starter relay. I got home last night and hooked it to what I remembered being the correct pin (the bottom most pin, I can't remember the number) and I got a high-pitched whining sound from the relay, but no start. Knowing that was wrong, I pulled the wire from the pin.

Now I'm back where I was: Good start, no charge.

I've searched the forum, but I didn't see anything helpful, and Frenzy is only a month off and I'm starting to panic.

Was that wire somehow exciting the alternator? If so, what pin does it need to jumper? If not, what the hell was it doing? And what happened to my alternator?

Thanks in advance for any help.

SeanR

How's that little idiot light on the voltmeter on the dash when you turn the key on. Not start, but on.

Alan

I think the wire on the starter relay was to bypass the transmission safety switch (not related to the alternator). Do you have a functioning alarm? if the alarm is disabled/removed you may need a jumper on the Z-plug - is one installed?

Alan

Shawn Stanford

Transmission safety bypass. Hmm... That explanation has some merit. I inadvertently tried to start the car in gear the other day and it wouldn't start. This seemed odd to me, although I'd never really tracked if it would start in gear before. As far as I know, there's no alarm on the car. I've never seen any evidence of it, but I haven't been looking, either.

I'll check when I get home.

Shawn Stanford

It lights when the key is turned on, before the motor is started. With the engine running I'm showing 11+ volts across the battery terminals, a little more at the jump post. No change when revving the motor.

Alan

Is anything plugged into the Z-Plug in the middle of the CE panel?

Alan

Shawn Stanford

Hi Alan.

Yes, there is a plug in the Z-socket. (Which I located thanks to your amazing CE panel graphic!)

Shawn Stanford

I found this thread about troubleshooting a non-charging alternator in an '82: https://rennlist.com/forums/928-foru...longish-2.html

There was a list of checks, one of which said to check the Z10 pin. But the Z connector only has 6 pins? So that got me looking for where in hell the Z10 pin is and I found another thread and this:So I checked pin 1 of the 14-pin connector and I found that with the key on I have 2v+ at pin 1, with 12v+ at the jump post. Does this mean that the exciter circuit is good, and that I should have the alternator checked? I lifted the car and looked at the alternator, and all the wires seem tight and proper.

And in another post was this:So, with the engine running, I should jump pin 1 to 12v (like the jump post), and at that point the alternator should start charging? And, if it does, the problem is the exciter circuit, and if it doesn't the problem is the alternator? Which is the 'proper' side? The side coming in from the firewall, or the side going into the motor?

Shawn Stanford

And from another alternator thread:So, if I understand what Alan is saying here: With the key on and motor not running, I have should have around 2v at pin 1 (I have 2.4v). If I do, I should check continuity from pin 1 to the exciter wire on the alternator (per Stan) or voltage (per Alan), and if there's no continuity (or voltage), then I need to start looking for a break a few inches up from the alternator (because it was likely left to hang), or run a daughter wire from pin 1 to the exciter connector on the alternator.

Is any of that incorrect?

Shawn Stanford

I have the same voltage at the alternator as I do at pin 1 (2.4v). With the motor running, I still have 2.4v at pin 1.

I read in other places that 12v is required to excite the alternator. So can I assume this is the problem? Can I test this by running a test wire from the jump post to the exciter wire on the alternator?

And, yeah, I should have mentioned up front: I have the Delco CS130 alternator.

Alan

If you have 2.4v at both the alternator and the the 14 pin connector with the ignition on and engine not running then the wiring is all OK.

If when you start the car the alternator doesn't generate it suggests an alternator issue - could be as simple as brushes/regulator.

Alan

Mrmerlin

if you rev the engine to 2500 rpm does it start charging? use a DVM on the hot post to verufy measurements

Chris Hansen

Did you go ahead and replace the headlight relay? I know they are pricey, but when mine went bad (no high beams) like yours, I had some wonky electrical behavior.

hagen454

Shawn just drive it down to the next frenzy. Kary has another new alternator! Actually I don't think he has even installed it yet.

Shawn Stanford

Well, the needle doesn't jump in the cab any more. I'll get a helper and give this a try.

That must be the one I sent him to replace the one he pulled from his car to put into mine at last year's Frenzy.

It's chrome!