Voltage fluctuation

[C.J. Roberts]

Alright, I've got another strange one. I have a digital Voltmeter added to the Muddog, (2002, 4.0, 170,000 miles), and in warm weather it's always shown 13.9 volts. Yesterday, it was displaying 13.5-6 volts. This morning, 14.1-2 volts. Later, back to 13.9. It's never done this before. Is this an early indicator of a failing Voltage Regulator? Or an, "They just do things like that occasionally"?
Follow up: If I wind up needing an external Voltage Regulator, does that mean a constant CEL?

 

[macleanflood]

Do you have a battery temperature sensor?

I'd bet you can correlate temperature change to voltage.

-Mac

 

[C.J. Roberts]

I'd bet you can correlate temperature change to voltage.

-Mac

I don't think so. It's ALWAYS shown 13.9 volts in warm weather, and the weather hasn't been cool here since April. Now in Winter, on a cold start, it'll crank 14.4, 5,or 6, but that's not the case here.

 

[macleanflood]

Do you have a battery temperature sensor?

What's the voltage as reported by the PCM?

I'd check ground wires.

-Mac

 

[C.J. Roberts]

Do you have a battery temperature sensor?

What's the voltage as reported by the PCM?

I'd check ground wires.

-Mac

As you know, the factory Voltmeter isn't very accurate, but even it showed slightly lower than normal. The digital gauge I have is wired through the old cigarette lighter circuit.

 

[jjvw]

I think the fix is to remove the digital volt meter so you quit diagnosing non-existent problems.

 

[B1Toad]

As you know, the factory Voltmeter isn't very accurate, but even it showed slightly lower than normal. The digital gauge I have is wired through the old cigarette lighter circuit.

I have a cigarette lighter plug in USB charger that includes a volt meter. Sometimes when I first start the Jeep, that voltmeter will jump to over 15 volts and start flashing. I unplug it then plug it back in and all is normal.

 

[KennethS]

I think the fix is to remove the digital volt meter so you quit diagnosing non-existent problems.

I have seen this many times on classic vehicle forums with folks who installed a temperature gauge in place of the idiot light start getting concerned about the coolant temps showing 200+ degrees. It was not an issue with the same conditions when the HOT light never illuminated.

 

[jjvw]

I have seen this many times on classic vehicle forums with folks who installed a temperature gauge in place of the idiot light start getting concerned about the coolant temps showing 200+ degrees. It was not an issue with the same conditions when the HOT light never illuminated.

We see it here frequently when people start watching their Jeep's ODBII engine temps while driving.

 

[Zorba]

I have a cigarette lighter plug in USB charger that includes a volt meter. Sometimes when I first start the Jeep, that voltmeter will jump to over 15 volts and start flashing. I unplug it then plug it back in and all is normal.

It would wig out over 15 volts?!?

A lead-acid "12 volt system" needs to tolerate 16 volts as an absolute minimum, I always designed for 18.

 

[B1Toad]

It would wig out over 15 volts?!?

A lead-acid "12 volt system" needs to tolerate 16 volts as an absolute minimum, I always designed for 18.

They probably didn't know that when they designed the product over in China. BTW my lead acid is an AGM.

 

[C.J. Roberts]

It would wig out over 15 volts?!?

A lead-acid "12 volt system" needs to tolerate 16 volts as an absolute minimum, I always designed for 18.

No, it was fine. I just didn't expect it. It's not acting up with this. I just never saw it do that before. Maybe it's not a problem. I just want to see whether it is or not.