2004 Silverado With Erratic Voltage

[lowcountry]

I have an 04 5.3 Silverado with 120,000. While driving, I looked at my voltage gauge and it was pretty close to 19 volts. I pulled over and popped the hood. Cranked it back up to check the voltage with my volt/ohm meter and it was back to 14.5 again. I stopped by advanced and had them test the battery and it was bad. You could see where a cell had been cooked on the top of the negative side. Drove home and the voltage stayed fine. Went to dinner that night and it went up to 17 volts. I decided to replace the alternator (internal voltage regulator) and belt since they were original and hopefully be done with it. Made a three hour trip yesterday and everything worked great. Cranked it up this morning, it went up to 19 volts. I turned it off and then back on and it dropped a little. Did that three times and it finally went back to normal. The directions for the alternator replacement were very specific since the voltage output is actually controlled by the computer. Should I start looking for a new ECU or is there anything else I can check?

 

Thanks,

[redvett]

The PCM does not control voltage on 2004 this system did not start until 2005 and only on #1500 series. I would look and a bad connection. Pos & neg battery cables from battery to starter and block.

 

 

I have an 04 5.3 Silverado with 120,000. While driving, I looked at my voltage gauge and it was pretty close to 19 volts. I pulled over and popped the hood. Cranked it back up to check the voltage with my volt/ohm meter and it was back to 14.5 again. I stopped by advanced and had them test the battery and it was bad. You could see where a cell had been cooked on the top of the negative side. Drove home and the voltage stayed fine. Went to dinner that night and it went up to 17 volts. I decided to replace the alternator (internal voltage regulator) and belt since they were original and hopefully be done with it. Made a three hour trip yesterday and everything worked great. Cranked it up this morning, it went up to 19 volts. I turned it off and then back on and it dropped a little. Did that three times and it finally went back to normal. The directions for the alternator replacement were very specific since the voltage output is actually controlled by the computer. Should I start looking for a new ECU or is there anything else I can check?

 

Thanks,

[lowcountry]

I will take a look at the cables. While doing some research, I have heard about the washer for the side post connections being one time use only. Anybody ever heard or dealt with this?