Alternator or..?

MidWesty · Post by **MidWesty** » Sun Aug 20, 2006 4:09 pm

'78 Rivi, 2.0L FI
I"ve noticed my alt light coming on after driving for say 30-45minutes. It's not actually coming full on, but is starting to flicker at that point. I've also noticed that I get no light when I first turn the key on which I know I'm supposed to. The battery is brand new, I'm not having any starting issues, the battery reads just shy of 14V when running with headlights on, but when I hook up my old school Sears analyzer and do a charging system volts test I'm showing about 11V when running. According to the book that is with the analyzer anything under 13.5 suggests faulty alt or VR. I used a little pocket alt tester as a second opinion and it also is saying faulty alt or VR. Now, I know the alt has to be "excited" into doing it's job. How would I go about testing to see if this is happening? I'm just wondering if the alt is good but unable to do it's job because of a breakdown in the system at the ignition/light whatever excites it into working. I'm not a real fan of the electrical system so if anyone can help and is able to put it into plain English it would be very much appreciated.

Thanks!

chitwnvw · Post by **chitwnvw** » Sun Aug 20, 2006 4:16 pm

Are you sure it's not a matter of your belt expanding when warm and starting to slip?

MidWesty · Post by **MidWesty** » Sun Aug 20, 2006 4:22 pm

I did actually think that was the initial problem, but I've had 3 people tell me that a belt is more apt to slip when cold and will actually stick better when warm. 2 of which are mechanics. I was all ready to change the belt. I checked the tension at rest and it's tight. I may go ahead and try it anyway. Cheapest option is what I always check first anyway.

Randy in Maine · Post by **Randy in Maine** » Sun Aug 20, 2006 5:06 pm

Could you humor me and check fuse #12?

MidWesty · Post by **MidWesty** » Sun Aug 20, 2006 5:51 pm

1 step ahead of you. All fuses are good. I do believe there may be some wiring issues though. The previous owner informed me "I did some of the wiring myself." That kind of worrries me but like I said it hasn't given me any other issues until now. The one thing that puzzled me from the beginning was the dash lights come on when I turn the key to the on position. It's like the headlights are on but they're not.
Anyway it's starting to look like I may have to get deeper into the wiring than I'd first wanted to.

Thanks!

Post by **Amskeptic** » Sun Aug 20, 2006 6:07 pm

MidWesty wrote:
I may have to get deeper into the wiring than I'd first wanted to.

The story of our lives. . .
Your symptoms might sort of possibly maybe hint at a suggestion of a rotor beginning to ground out as the alternator bearings allow end play that should not be there.
Please pull the belt and try to move the pulley fore and aft. Any clunkishness, and there you go.
Colin

MidWesty · Post by **MidWesty** » Sun Aug 20, 2006 6:23 pm

Thanks Colin.
Now, about that pesky light not coming on when I turn the key.
How would I test for the source of it's problem? If the #12 fuse is good then it should be working as designed, correct? If not, what else could be causing it to not trigger at the turn of the key?

Thanks again!

chitwnvw · Post by **chitwnvw** » Sun Aug 20, 2006 6:51 pm

Wow, I'm getting hooked now! :smt118

Can't find my Muir right now, but doesn't he go through what the different alt light scenarios tell you. I remember I had an alt light that wouldn't ever go out, had to pull one of the battery wire off to kill it... :smt017

dingo · Post by **dingo** » Sun Aug 20, 2006 9:15 pm

from type2.com:

The alt-light is effectively connected *between* battery (+) and alternator output, so it indicates when either side is low, though not both(!).
Hence it's on when the ignition is on but before the engine is started and also if the engine is running but the battery getting low or the alternator isn't producing output. It actually performs an important job in providing the initial excitation current to the alternator's field windings.

also....a faulty diode in alt. can cause intermittent dash light

MidWesty · Post by **MidWesty** » Mon Aug 21, 2006 6:24 am

Thanks dingo. I'll be tracing some wires later this evening trying to back track what the PO did. While crawling around under it last night I did come to find out that all the wiring seems to be there for an aux. battery hook up. At least some good has come from it.
I'm going to go ahead and pick up an alt anyway I think. So far everything seems to point in that direction.

Thanks again!

Post by **Amskeptic** » Mon Aug 21, 2006 10:36 am

Try this:
If light comes on (ignition-on engine-off) only when you disconnect voltage regulator connector, rotor is grounded out.
PLEASE UPDATE so we can file away yet another solution.
Colin

Itinerant Air-Cooled

Itinerant Air-Cooled

Alternator or..?

Alternator or..?