Strange electrical goings on

jhaynie · #1 (**permalink**) 10-03-2003, 07:36 PM

These cars are so much fun..

My wife and I are coming back from dinner tonight from a restaurant in a nearby town (ie. 30 miles down dark country roads). All of a sudden this happens.

First the tech parts:
351W, single wire type alternator, MSD ignition, Holley FI, headlights are on.

What happened:
The headlights and dashlights got REAL bright. The ampmeter pegged at over 60 amps at 2000rpm. This stayed like this for about 7 minutes and then everything dimmed down to the point where there were not much headlights below 2000rpm.

Then after a couple of minutes it stabilized where it had been, about 30amps at 2000-2500rpm and the headlights don't dim.

I tell you when everything went bright as the moon in the sky, I thought I was looking towards an electrical fire and a long walk home. I'm thinking voltage regulator, bad ground, or something else I know nothing about. ANY SUGGESTIONS??

427sharpe · #2 (**permalink**) 10-03-2003, 07:42 PM

The internal regulator inside the alt is probably going....it caused the 'spike' in voltage and the alternator shut down (the dimming) and when it cooled down enough, started to work again. I would replace the regulator, and make sure the contacts are CLEAN and getting full contact. A good suggestion might be to put a HD regulator in since you'll be opening the case anyhow.

jhaynie · #3 (**permalink**) 10-04-2003, 05:53 AM

Are there contacts in the MSD distributor. I thought these were modern electronic ignitions that didn't have contacts?

petek · #4 (**permalink**) 10-04-2003, 08:50 AM

This is one of those times that a voltmeter would be helpful. We'll assume from the brightness of the headlamps that the voltage climbed up pretty high. How high? Who knows! Obviously not high enough to blow out the headlamps or MSD box.

It *could* be the internal voltage regulator in the altenator ... but it could also be a bad ground to the engine (or maybe the battery). What I'm thinking is that a bad engine ground would make the voltage regulator in the altenator think that the voltage in the rest of the car (i.e. the battery) was too low. The v-reg would then bump up the voltage and attempt to bring the battery voltage back up.

I'd go through and make sure all of the connections (battery, altenator, starter, ground to the engine, any connection with a wire around 12 awg or less) were clean and tight.

Next on the list would be to see if you can get the problem going with the car in the garage. If you can get the problem to come back, take a voltmeter and measure the voltage between the engine and the chassis ground and then battery ground. You should not see any voltage, but if you've got a bad ground, you'll see some voltage.

Excaliber · #5 (**permalink**) 10-04-2003, 09:58 AM

The regulator is electronic. The "contacts" are where the regulator bolts or fastens TO the body of the alternator (usually inside). Often "thermal grease" is used to assure a good "contact" as well as dissapate heat buildup.

Ernie

excelguru · #6 (**permalink**) 10-04-2003, 09:03 PM

Did you notice any weird lights in the sky? Did you get home to find that the 30-minute ride really took eight hours and you can't account for the missing time? Did you find any strange marks on your body? Have you had any dreams about big-eyed beings performing strange experiments on your car while you watch helplessly? (Insert "Twilight Zone" music here...)

Man, that would freak me out, too. You gonna bring it to ATS sometime? Let me know when you do.

jhaynie · #7 (**permalink**) 10-06-2003, 06:58 AM

Keith,
I tried to go to ATS last week, but they had a couple of hundred "tuners" coming in on Friday and Saturday to use the dyno.

Pete,

I just finished a nearly complete rewiring of the starting system, with all new cables, solenoid, and new connectors. I don't think grounding is a problem. Although that made me think, maybe the lights should be that bright and I have some bad connection somewhere causing voltage loss, or have had a bad voltage regulator for some time, not allowing the alternator to put out full volts (or amps).

What should the Voltage be at the alternator at idle speed. I know on my boat it is about 13.5 volts (14.6 at higher rpm), on the car yesterday I measured 12.3, that seemed low, but it was consistent at several grounding points in the car.

John