Spidey944

No one has mentioned the cables or grounds in the whole thread? AMAZING!!

Wipeout

I checked the connections on the back of the alternator and cleaned them off (not very dirty, however. Cleaned a few of the grounds that I had easy access to.

13.7 with only the engine on. With blower, lights, defroster, radio; dropped to 12.8. Turned defroster off, up to 13.4. Seems largely to be a load issue, no?

Spidey944

True, but if the ground cables are cracked or corroded inside the sheathing, it can cause a high resistance and give a similar condition.

Wipeout

True enough, but I doubt checking/cleaning all the grounding points would detect that. And I'd expect much more electrical woes. I'll look into the rest of the ground points (since I'll have the thing in the air soon), but I'm not overly worried (yet). Wish the earlies had a voltmeter in the cabin!

marky522

If your dropping to 12.8 with everything off i would guess your alternator is on the way out. I would do as Spidey suggested and check your main ground, and Positive terminals. An easy way to check the wire for excessive resistance is take you DVOM with the car running and all loads on put your leads on the neg term and the point on the block where the ground cable bolts. Shouldnt be more than .5 Volts. The Pos you want to check the lead on the back of the Alt to the Pos terminal again only a .5V max or you have excessive resistance in the cables that is consuming power.

Mark

Wipeout

I get 12.8 with everything ON, not off. That make a difference?

DarylJ

I'm sure that's what he meant.

Yes...problem. Your battery should be 12.8. If you aren't above that with all loads on, you battery isn't charging and is making up the difference between what the alternator puts out and what you are asking for....which is why the light is on.

So, as already suggested, you may have a cabling/grounding issue, or the alternator is just getting weak or has a bad voltage regulator. While having a newish VR makes it less likely to be the cause, don't rule it out. They can be and sometimes are bad out of the box.

marky522

Yes, with all loads on 12.8 is too low. A fully charged battery is 12.6V, your car should be putting out over 13V with all loads on, to keep your battery charged and keep all your loads operating.

Mark

tailpipe

sounds like a diod or two has dropped out of his alternator have it checked if its just been replaced have them do it again

Wipeout

Going to take my other alternator in to get rebuilt, may have this one tested at the same time. Doing belts soon so swapping in a new alt isn't overly difficult!

Kburke

what was the result I have a late model and this has been a problem for me for a long time

Wipeout

Result is that I rear-ended someone and likely totaled the car. Never did get a chance to investigate further.

Luis de Prat

Sorry to hear that! Give Ian a call at 944 Online. He may be able to help you out!

Wipeout

It's the frame that's probably FUBARED. Insurance was all set to fix it until things started to get taken apart. Still waiting for final verdict.

Have my eye on a possible replacement to keep me in 944-land.

FRporscheman

Darren, I'm sorry for you! I hope you get a reasonable check from the insurance company. If you need someone in SF to look at a car for you let me know.