1991 Chevy Van power loss while driving

COLLEEN DUNN

MEMBER
1991 CHEVROLET VAN
V8
2WD
AUTOMATIC
57,000 MILES

After driving about an hour the back speakers stopped working. Then the front speakers went. Shortly there after the LED's on the dash dimmed, the battery indicator started flashing and the speedometer changed to 88. I was NOT driving at 88 mph. It took about another hour to get to our destination. We turned off the van for about an hour, we had to use the jump box to start it. It worked fine for about another half hour, when it all started again. Within the next half hour the whole dash was dim and inaccurate. The battery and alternator pass the tests. The van is a conversion that has many electrical devises and headaches. There is a toggle switch that disconnects the battery through a battery isolator, but that seems fine, because being off over night, the van still starts. There also is an additional battery isolator that connects the main battery, 2nd battery, alternator, and ignition.

Where should we start to look for the problem?

3 Replies

CARADIODOC

MECHANIC
33,916 POSTS

Hi colleen dunn. Welcome to the forum. All of these symptoms are typical of an intermittent generator. It probably was tested while it was in the working state. You'll have to catch it while the problems are acting up, then use a cheap digital voltmeter to measure the voltage between the two battery terminals. You must find between 13.75 and 14.75 volts while the engine is running. If it is low, suspect the generator, but if you want to double check, measure the voltages on the large wire bolted to the back of it and the smaller wire plugged into the side of it and post the results here.

Caradiodoc

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Wednesday, June 23rd, 2010 AT 12:39 AM

COLLEEN DUNN

MEMBER
2 POSTS

We replaced the alternator as suggested and it worked great. It is squealling like a pig constantly though. After about 30 hours the dash lights started going whacky again, this time we only drove about 15 minutes. We had to use the jump box again to start it. Now what?

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Friday, June 25th, 2010 AT 10:11 AM

CARADIODOC

MECHANIC
33,916 POSTS

It sounds like the new generator is defective. There's no way to sugar-coat it. GM went from the second best generator to the world's worst pile in 1987. Due to its design, it is prone to developing voltage spikes that affect the many computers on the van. What more and more professionals are finding out is the number of repeat failures can be reduced by replacing the battery at the same time. The battery will likely work perfectly fine in an older car but as they age, they develop increased "internal resistance" which limits their ability to dampen those voltage spikes. Even when replacing the battery with the generator, it is common to go through four to six generators in the life of the vehicle.

Caradiodoc

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Friday, June 25th, 2010 AT 1:19 PM