1994 voltage loss from engine to interior

[Thor Wicklund]

I have a 94 k2500 6.5 diesel with a electrical issue. I have 14 volts at both batteries and at alternator but as soon as I turn something on, volt gauge in dash drops to 12 volts. Verified 12 volts at cigarette plug. If I go back out to engine, voltage is close to 14 volts at batt/alt. What would cause losing 2 volts from engine bay to interior?? Thanks

 

[thegawd]

bad grounds..... under the heater core there is a ground connection to the frame. there is another ground from this same spot to the rear passenger side of the the engine block. well at least on the gassers.... not sure with the 6.5 but the cab is the same and I assume the ground locations would be aswell....

 

[steveed]

^^What he said.


Initial guess based on the problems that most people have with electrical issues in these trucks is bad grounds. Probably corroded ground wires and/or connections.

If you go here there are wiring diagrams. It doesn't look like there is a full wiring diagram manual for the 94 but I am guessing you can use the 93 or 92 to locate the various ground wires.

 

[Schurkey]

While "bad grounds" could be the problem, it's just as likely to be voltage drop on the power side.

Corroded connections anywhere in the circuit--power supply, or ground--will cause loss of voltage.

If you're LUCKY, you'll find one connection or cable that's corroded/damaged. It's also possible to have a little corrosion in fifteen different places, each one adding to the power loss.

 

[LC2NLS6]

If GM did the same thing they did with the G body cars, everything runs through the ignition switch, which can wear out and cause low voltage. Have fun replacing that if its in the column...

 

[thegawd]

The ignition switch is easy to replace. taking the dash apart is the hardest part but its not hard. I have removed 3 from a junkyard but started to remove at least a dozen, I couldnt believe how many people spliced them in with butt end connectors or worse! like WTF? one bolt holds the plug to the firewall. remove the bolt and remove the plug. simple as shìt.