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Chris
Chris, Shop Foreman
Category: Dodge
Satisfied Customers: 13365
Experience:  Dodge/Cummins and Chrysler Certified Master Tech
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Voltage randomly jumps to 18 or so, according to the dash

Customer Question

voltage randomly jumps to 18 or so, according to the dash gauge, then drops back to normal or down to about 8 volts. Then returns to normal. Some days it doesn't act up as much as others, but it is anoying. When it spikes, my radio shuts off (goes into surge protection mode) until the voltage drops. Not sure what's going on. Each time this happens, the tachometer and speedometer react as well. The speedometer does not work any more. The odometer does. It has the cable and electrical harness set up.
JA: Have you checked the fuses?
Customer: Not the fuses or it would just shut off.
JA: What year is your Volts?
Customer: 92 Dakota 5.2L v-8 4x4
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: New ECM and battery. New relays. The relays get hot and shut down the truck sometimes. I swap them around and it starts again.
JA: Anything else you think the mechanic should know?
Customer: not at this time.
Submitted: 10 months ago.
Category: Dodge
Expert:  Chris replied 10 months ago.

Hello, my name is ***** ***** I will be assisting you today. Sounds like an internal alternator or a short to ground in the alternator field circuit(s). Has the alternator been replaced?

Chris

Expert:  Chris replied 10 months ago.

Thank you for the positive rating and bonus!

Chris

Customer: replied 10 months ago.
checked with my re-builder and he said, if it is charging at all that it is not the alternator.
Customer: replied 10 months ago.
I have been told by one mechanic that it may be the dash panel. could be cracked. since the ECM controls the voltage, it gets mixed signals. What do you think?
Expert:  Chris replied 10 months ago.

If the negative side of the alternator field windings short to ground and "full field" the alternator, then it will ramp the voltage up to maximum. Could be a short in the wiring between the alternator and PCM. And you are correct about the PCM regulating the voltage. I doubt it is a crack in the dash panel. Try monitoring the voltage with an external volt meter. See if it is really climbing up to 18 volts.

Chris

Customer: replied 10 months ago.
It is actually ramping up. I can see it in the headlights and the radio shuts off as an auto protect, every time it surges. When the voltage drops to around 8v, I see the lights dim. The wipers will slow, etc., so it is an obvious voltage issue.
Another thing I do is to tap on the breaker box under the hood or move the relays around. The shut off relay, fuel relay, etc. are all the same. They sometimes get very hot to the touch. I have even had the shut off relay kill the motor from time to time. Doesn't matter if the engine is hot or just starting out. What would be causing these relays in the box to get so hot?
Expert:  Chris replied 10 months ago.

Well relays will get hot somewhat, but if the voltage is too high, that will increase the temperature. By the way, did you replace the PCM for this concern?

Chris

Customer: replied 10 months ago.
Expert:  Chris replied 10 months ago.

Ok, then it is probably not another PCM issue. That leaves a short in the field circuit wire (harness rubbing somewhere to ground) or a bad alternator.

Chris

Customer: replied 10 months ago.
It's been frustrating me for months. I will try to have a look at the alternator again. Would there be a way to test or trick the alternator into doing this if it were an internal issue?
Expert:  Chris replied 10 months ago.

Well the test would be to disconnect the field circuit wire at the alternator that goes to the PCM. If it still tends to overcharge, then it has to be the alternator. If it no longer overcharges, then suspect a wiring issue.

Chris

Customer: replied 10 months ago.
Thanks. Let me get back to this later and I will let you know what I find out.
Expert:  Chris replied 10 months ago.

Sounds good my friend, and you are welcome!

Chris