Wyatttank

So I have a 2003 chevy 1500 with about 293000 miles on it. I have been having voltages drops while driving. The voltage will drop only in the cab to almost 9 volts at times. The abs light l, parking brake light and sometimes the airbag and security light will come on too. This happens when the hvac fan speed is above 1 sometime it even happens on speed one also. It also happens if the music is turned up or if any other accessories are on in the cab. The voltage is normal everywhere else on the truck the only voltage drop is in the cab. I located all of the in cab grounds and cleaned them. I have tried swaping the dash cluster, the hvac module and it has a new transfer case control module. I have also taken apart and checked all the connections on the abs module. It also have a new fan restor. I've tried unplugging molutiply different accessories like the fan motor etc and nothing fixed it. My mechanic friend hooked up his fancy snap on scanner and determined it was not the ecu. I have also tryed putting different alternators on it and nothing worked. When it started I had no after market accessories in the cab. I can't seem to find where the voltage drop is coming from. If anyone has ran into this let me know

chem_man

A couple of things to look at. One, check the little black wire that comes off the negative battery cable at the battery and make sure that where it connects to the body is clean and tight. Second, look at the ends of your battery cables, both positive and negative, and see if there is any green grunge visible. You might want to peel the insulation back ever so slightly to see if there is any green grunge under the insulation. If there is, it is time to replace the battery cables.

It would not surprise me if both battery cables had deteriorated due to age and mileage.

If you can, examine the 12 VDC wire(s) that go into the underhood fuse center and see if there is any corrosion/green grunge there too.

Good Luck!

Wyatttank

Yes everything under the hood is clean I did that a while ago and I had also removed all the grounds under the hood and on the frame and in the cab and cleaned them thoroughly. Like I said if you check anything electronic components under the hood or anywhere on the truck they are all getting the correct voltage all the time. The only place that is having low voltage it inside the cab.

chem_man

You do not want to test for voltage. Go point to point and measure the resistance using the ohms scale, and bend/flex the wire in between the two test probes. The resistance should be less than an ohm or two at all times. Also double check the wire that goes from the alternator to the battery - they sometimes go bad.

You can measure the correct voltage on a wire that has an internal break. The connection will not break down unless several amps of current are being drawn through the wire causing the resistance in the area of the break to increase which then causes the voltage to drop.

Wyatttank

i already checked everything under the hood that runs into the can tryed a new alternator and battery and all the wires are good

Wyatttank

UPDATE I figured out a fix. I ran a new ground wire directly from the dash to the frame everything works perfectly now!!!!!!

Doug Morgan

I have a 2015 Chevy Silverado. I was driving in a parking lot and was turning into a parking space it completely shut off. A message came up that I had 3 keys and also to roll the driver's window down and back up.
Any suggestions on how to fix it?