Charging system problem 89 chevy truck?

Hi guys, I have been reading some of the problems that some of you had with the 89 chevy pickup. The problem I am having has to do with a wierd drop in voltage I am getting intermidantly. While I am driving, the voltage will drop down to what looks like battery power, then will pop back up like its back to charging. I took back the alternator thinking it was a regulator problem, but that wasn't it. The battery checks out good also. Could it be the wire that controlls the regulator? I had also perviously had the EGR valve DTC go off. I did have the exhaust replaced, but havent tripped a code on that since.I understand about checking the battery leads, but what is the proper value I should pull off of these wires. I don't see the lights dim or anything, but the volt gauge goes up and down. This seems to happen no matter what I have on, so I don't think it is a short. I would appreciate any information you can give me.

Is this an original / new or rebuilt alternator?
My guess would be sticking brushes losing contact with the armature.
If not that then it may be some kind of wiring short. I have no clue were to start???

Hope that helps!!!!

Hi guys, I have been reading some of the problems that some of you had with the 89 chevy pickup. The problem I am having has to do with a wierd drop in voltage I am getting intermidantly. While I am driving, the voltage will drop down to what looks like battery power, then will pop back up like its back to charging. I took back the alternator thinking it was a regulator problem, but that wasn't it. The battery checks out good also. Could it be the wire that controlls the regulator? I had also perviously had the EGR valve DTC go off. I did have the exhaust replaced, but havent tripped a code on that since.I understand about checking the battery leads, but what is the proper value I should pull off of these wires. I don't see the lights dim or anything, but the volt gauge goes up and down. This seems to happen no matter what I have on, so I don't think it is a short. I would appreciate any information you can give me.

maybe the plugs to the alternator are loose or have some junk built up on the connections.

Thanks for the replys. Unfortunately it has done the same thing with two different alternators. I am going to try and replace the battery leads this weekend. I have noticed that the volt meter on the dash is wrong half the time. I was kind of curious why I never got an alternator light when the voltage went down. Anyone know how I get the reading on the volt meter? I used a DVOM and saw that the alternator was producing 15.1 (when I wasn't having one of those episodes with barely battery voltage, but showed on the inside as being around 13.5. Anyone know if there is some kind of sender unit for the voltage? Or maybe when I replace the positive main this will cure that misread?

Thanks for the replys. Unfortunately it has done the same thing with two different alternators. I am going to try and replace the battery leads this weekend. I have noticed that the volt meter on the dash is wrong half the time. I was kind of curious why I never got an alternator light when the voltage went down. Anyone know how I get the reading on the volt meter? I used a DVOM and saw that the alternator was producing 15.1 (when I wasn't having one of those episodes with barely battery voltage, but showed on the inside as being around 13.5. Anyone know if there is some kind of sender unit for the voltage? Or maybe when I replace the positive main this will cure that misread?

if your getting 15.1V from the altenator. then what's the voltage on the battery and the voltage at fuse panel? if the voltages are the same as the alternator voltage then maybe it's just your gauge acting up. i have an 89 silverado and it does the same thing as yours. the gauge sometimes says 10V but i check with a DVOM and it says 14.5V. maybe this is why the alternator light hasn't come on because the voltage isn't as low as it is on the volt gauge.

if your getting 15.1V from the altenator. then what's the voltage on the battery and the voltage at fuse panel? if the voltages are the same as the alternator voltage then maybe it's just your gauge acting up. i have an 89 silverado and it does the same thing as yours. the gauge sometimes says 10V but i check with a DVOM and it says 14.5V. maybe this is why the alternator light hasn't come on because the voltage isn't as low as it is on the volt gauge.

I have noticed it is happening a lot more frequently then it was. I have had an opportunity to confirm that the battery is getting about 15.1 after start up, and after being run it is getting about 14.1. All this time the voltage on the gauge is saying about 10. Of course I am still getting no battery/alternator light. Anyone have a schematic so I can trace the path of the voltage going to the pannel? I know the pannels have had some problems especial with the spedometer. I know there is a company that fixes them, but I want to make sure that it is in the pannel before I invest in fixing the panel.

Yea, I got wiring diagrams, I will have to look in the archieves for an 89. I have to go to work right now, so I will get back to you this evening.

Yea, I got wiring diagrams, I will have to look in the archieves for an 89. I have to go to work right now, so I will get back to you this evening.

I would appreciate any help you could give me. If you need my e-mail address to send it to, then let me know.

You need just the starting and charging diagram? Or complete chassis electrical? You can give me E-mail in a private message or here whatever u want. I think I only have this diagram in paper form. I need to scan it and have it put on a floppy disk then download into my computer. Or you could give me your address and I will mail it too you.

You need just the starting and charging diagram? Or complete chassis electrical? You can give me E-mail in a private message or here whatever u want. I think I only have this diagram in paper form. I need to scan it and have it put on a floppy disk then download into my computer. Or you could give me your address and I will mail it too you.

skipr, you have PM. I hadn't heard back from you and I just wanted to make sure you got it.

Yea I got it. Didn't you get my PM reply?