Electrical issues after heater core replacement

[cotopaxidude]

I recently replaced the heater core in my FZJ80. Since then I’ve been having electrical issues. First the ABS light came on, then the instrument panel illumination stopped working. The tachometer now only works intermittently. It’s not just the instrument panel—the tail lights don’t work either. The grounds in the engine compartment seem to be OK, and I removed and reinstalled the instrument panel. Now I don’t know what to do next. Did I make a mistake reassembling the dash after replacing the heater core, or is it just a coincidence? Any suggestions greatly appreciated.

 

[NeverFinis]

Probably a loose connector.

Did you check the other grounds, for example the ones in the kick panels.

Also, did you have the battery disconnected while doing all of this?

 

[tech_dog]

Missed connections on switches, buttons and indicator lights can leave open circuits and make things stop working, but you've got symptoms related to 3-4 different connectors under the panel. You'd have to have flailed a lot for it to be multiple mistakes on reassembly.

Did anything bad happen to your wiring harness as you were doing the job?

I'd check your battery and alternator health as a start. You can get odd symptoms if you have power issues, so rule that out first.

 

[cotopaxidude]

Thanks for those responses. The battery is new, and the alternator is putting out 14.7V. The only issue that I know of with the wiring harness is that there are wiring remnants of an aftermarket car alarm that I removed when I bought the truck in 2011.

I’ve mostly had the battery connected. I have not checked all those grounds, such as the ones in the kick panels. I don’t have factory manuals, but this list will help me find them, thanks.

Now I have a new problem—misfiring cylinders, all of them. The spark plug wires, distributor cap, and rotor are all new.

 

[NeverFinis]

Having the battery connected and then disconnecting an airbag will generate an airbag light. This has to be cleared otherwise it will be always on.

The FSM and EWD are in the resource sections here.