Electrical Problem

[77tonner]

I never know which board to post to with electrical problems. Over the last 6 months or so, I have been chasing an electrical problem.  I have noticed that my voltmeter on the truck surges from a steady 13-14V quickly up to 16V or so, then falls back down to 13-14V, and repeats.  Then, it goes the opposite way, down to 9-10V and goes back up, and repeats.  After about 5 seconds of this, it goes back to 13-14V and stays steady.  Then in about 10 minutes, it does again. It's really annoying because every light in the trucks flickers. I have wiggled wires all over, and the only wire that make this occur is the two wire plug to the voltage regulator on the alternator.  Could this really be the problem?  If so, anyone know how I can go about diagnosing it?  Is it the plug or the voltage regulator?

Any help would be greatly appreciated.

Thank you in advance

BTW...1977 Chevrolet C30 Scottsdale with 350 4 bolt.

[VileZambonie]

place a voltmeter across the battery terminals with it running and watch the voltmeter. See if it is the same as your gauge.

[Lt.Del]

That happened to me once.  Each time I would go over a bump,the  volt guage either went down, or up. When it went down to 10 or lower, i would purposefully hit a bump to jog it again.

When I had time, i looked at the alterntor.  The red positive wire that is connected to the bolt-type connecter on back of alternator was loose. It was such a way where I couldn't tighten it up.  It just spun loosely inside the alternator.

Went to the slavage yard, got a $10 alternator, and was back in business.

Moral: check you connections everywhere.  I am no alt. expert, but it could also be inside the alt.  the diodes and stuff. May have to get a new one.  

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

Edited by: SgtDel  at: 3/28/07 5:54 am

[77tonner]

I will try putting a voltmeter again across the terminals and see it it matches what I see in the cab.  It does roughly match when the problem is not occurring, but I have not been able to thoroughly check it out.  I will be doing that today.  One thing I have noticed is that bumps really do not seem to make the problem, it actually occurs most of the time when engine rpms are dropping when coming to a stop.  It will last for like 5 seconds, then does not usually occur again.  It does also happen cruising on the freeway though at 3100 rpm or so.

Thanks for the quick responses...

[Lt.Del]

I'd get that alt checked out after you do the voltmeter test.   I had another similar problem on my way to the last North Wilkesboro Winston cup race in North Carolina many years back.  I saw the volts continually drop going through Winston-Salem.  I stopped at an auto parts store and bought a new fan belt.   That did the trick.  

SgtDel
aka "Andy"

www.delbridge.net

1979 Big 10 383 stroker
1991 Blu 'Burb 3/4 ton 4x4

Edited by: SgtDel  at: 3/28/07 9:36 pm