Intermittent Elec Problem

rtb1259 · February 8, 2011

Background. 2004 Silverado that I have owned since new. Added a second battery 2 years ago. Upgraded to 145 amp alternator 2 years ago. Voltmeter never moved off approx. 14 when the truck is running, no matter what accessories I turn off and on.

Took the truck to the dealer for cooling flush and tranny filter change around christmas. When I got it back, that night was driving and voltmeter drops to 12 and lights dim and flicker. Voltmeter jumps between 12 and 15 for about 2 minutes, and lights are flickering. Suddenly voltmeter goes to 14, and everything is normal. I think its a fluke, and not concerned.

It has done it several times since then. Sometimes last for 30 seconds, sometimes 20 minutes. May do it twice in a day, or may not do it for a week. Sometimes when the truck is first stated, or when I am doing 65 on the highway. I drove 900 miles and didn't do it once. Does it with lights on or off. You can hear the blower on the heater, slow down. I turn on and off things, but cant make it happen. When it does happen, I turn things off and on, and doesn't affect it. Sometimes the voltmeter just drops to 12 for a little while or long while, and sometimes it flucuates up and down. Always comes back up to about 14.2 and everything is fine.

I have replaced the alternator, disconnected second battery, pulled and dielectric grease all fuses and relays under the hood, swapped batteries around.

Anyone got any ideas.

jrrod2004 · February 8, 2011

Background. 2004 Silverado that I have owned since new. Added a second battery 2 years ago. Upgraded to 145 amp alternator 2 years ago. Voltmeter never moved off approx. 14 when the truck is running, no matter what accessories I turn off and on.

Took the truck to the dealer for cooling flush and tranny filter change. When I got it back, that night was driving and voltmeter drops to 12 and lights dim and flicker. Voltmeter jumps between 12 and 15 for about 2 minutes, and lights are flickering. Suddenly voltmeter goes to 14, and everything is normal. I think its a fluke, and not concerned.

It has done it several times since then. Sometimes last for 30 seconds, sometimes 20 minutes. May do it twice in a day, or may not do it for a week. Sometimes when the truck is first stated, or when I am doing 65 on the highway. I drove 900 miles and didn't do it once. Does it with lights on or off. You can hear the blower on the heater, slow down. I turn on and off things, but cant make it happen. When it does happen, I turn things off and on, and doesn't affect it. Sometimes the voltmeter just drops to 12 for a little while or long while, and sometimes it flucuates up and down. Always comes back up to about 14.2 and everything is fine.

I have replaced the alternator, disconnected second battery, pulled and dielectric grease all fuses and relays under the hood, swapped batteries around.

Anyone got any ideas.

I think it is the truck computer messing with the output (variable output)...but what is interesting is the fact that it does it while the lights are one which rules out that programming issue...

rtb1259 · October 13, 2011

Still need help with this problem.

Update: Once the weather warmed up, I did not have a problem with the voltage gauge dropping. I ran all summer without an issue. I did change the Alt feed cable to 2 gauge, Power cable to fuse box to 2 gauge. Now that the weather is cooling off, it appears to be starting again.

This problem is becoming aggrevating.

Does anyone have any ideas to check?