Voltage jumping around...goes up to 17.50!! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bryanw1968 · 05-16-2009, 04:06 PM

The truck runs fine but a few weeks ago I noticed that the voltage has started to go all over the map. From 12, to 17.50 and everywhere in between. I replaced the starter thinking that the internal voltage regulator was shot. Had no effect. I've checked all my wiring and everything "appears" to be good. I have electric fans and disconnected those thinking that maybe one of the relays was causing problems but still nothing. Now, the strange part. When I turn the truck off and then turn the key to on, the starter seems to make a chunk kind of noise. Could the ignition switch itself be the problem or possibly my starter. As far as I know the ignition switch is 40 years old. The starter is a CSR high torque mini starter and is only a couple of years old. Any advice is appreciated! Oh yah ignition is all MSD, not that I think ignition could be the problem.
B

cdowns · 05-16-2009, 04:47 PM

starters dont have anything to do with regulators

altenators have internal regulators

first before spending money it might b wise to unhook battery and start cleaning all connections INCLUDING ground connections

Wrenchbender Ret · 05-16-2009, 04:50 PM

There is no voltage regulator in the starter. The alternator controls the charging system. The 73 up have a built in regulator & the older ones have an external regulator. The regulator is probably bad. It could be a bad ground from the engine to the body or if it is the external regulator it could have a defective ground. It would be a good idea to put a service voltmeter across the bat & see if it agrees with the instument panel meter. Its possible the meter in the dash is bad or not grounding good. You better fix it imediatly. It will ruin the battery & electrical components.

bryanw1968 · 05-16-2009, 05:20 PM

I realize that there isn't a regulator in the starter ;-) I just meant that if something were internally shorted out could it affect things? I do have an external regulator but it is not wired into my circuit. The alternator I have is later model and is internally regulated. I replaced the alternator and have the same result as I too thought that the regulator in the alternator was bad.

The I took a reading at the battery and at the meter. They are the same.
I'll clean my grounds from both the battery to the block and from the body to the frame and see if that gets me anywhere.
Thanks,
B

bryanw1968 · 05-17-2009, 11:04 AM

Fixed it!
After checking all the grounds I started following the alternator wires all the way back to the main harness and found the problem. The connectors going into the factory wiring had gotten wet inside the loom and electrical tape and corroded very badly. Two of the wires fell apart in my hand. Everything is back to normal now. Thanks for the replies.
B

05-16-2009, 04:06 PM	#1
bryanw1968 Senior Member Join Date: Jul 2006 Location: Leander, Texas Posts: 850	Voltage jumping around...goes up to 17.50!! The truck runs fine but a few weeks ago I noticed that the voltage has started to go all over the map. From 12, to 17.50 and everywhere in between. I replaced the starter thinking that the internal voltage regulator was shot. Had no effect. I've checked all my wiring and everything "appears" to be good. I have electric fans and disconnected those thinking that maybe one of the relays was causing problems but still nothing. Now, the strange part. When I turn the truck off and then turn the key to on, the starter seems to make a chunk kind of noise. Could the ignition switch itself be the problem or possibly my starter. As far as I know the ignition switch is 40 years old. The starter is a CSR high torque mini starter and is only a couple of years old. Any advice is appreciated! Oh yah ignition is all MSD, not that I think ignition could be the problem. B

05-16-2009, 04:47 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	Re: Voltage jumping around...goes up to 17.50!! starters dont have anything to do with regulators altenators have internal regulators first before spending money it might b wise to unhook battery and start cleaning all connections INCLUDING ground connections __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

05-16-2009, 04:50 PM	#3
Wrenchbender Ret Registered User Join Date: Oct 2005 Location: Overland Park, Ks. Posts: 5,208	Re: Voltage jumping around...goes up to 17.50!! There is no voltage regulator in the starter. The alternator controls the charging system. The 73 up have a built in regulator & the older ones have an external regulator. The regulator is probably bad. It could be a bad ground from the engine to the body or if it is the external regulator it could have a defective ground. It would be a good idea to put a service voltmeter across the bat & see if it agrees with the instument panel meter. Its possible the meter in the dash is bad or not grounding good. You better fix it imediatly. It will ruin the battery & electrical components.

05-16-2009, 05:20 PM	#4
bryanw1968 Senior Member Join Date: Jul 2006 Location: Leander, Texas Posts: 850	Re: Voltage jumping around...goes up to 17.50!! I realize that there isn't a regulator in the starter ;-) I just meant that if something were internally shorted out could it affect things? I do have an external regulator but it is not wired into my circuit. The alternator I have is later model and is internally regulated. I replaced the alternator and have the same result as I too thought that the regulator in the alternator was bad. The I took a reading at the battery and at the meter. They are the same. I'll clean my grounds from both the battery to the block and from the body to the frame and see if that gets me anywhere. Thanks, B

05-17-2009, 11:04 AM	#5
bryanw1968 Senior Member Join Date: Jul 2006 Location: Leander, Texas Posts: 850	Re: Voltage jumping around...goes up to 17.50!! Fixed it! After checking all the grounds I started following the alternator wires all the way back to the main harness and found the problem. The connectors going into the factory wiring had gotten wet inside the loom and electrical tape and corroded very badly. Two of the wires fell apart in my hand. Everything is back to normal now. Thanks for the replies. B



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