alright i bought this truck about a month ago and when i got it i turned the lights on and "flash" low beams out, turned high beams on "flash" highs out. as soon as i replaced the lights turned them on then driver side went out completely and passenger side high beam worked so i replaced them both again with a new headlight switch they seemed to work fine just trying them so i left them alone, also had blown brake lights so replaced them they worked in park so i thought i was good. i took it to a friends house killed the truck hung out until dark and thought i would check everything without the truck running and with key on or off tried the head lights and brake lights nothing. started the truck everything worked so i left then 10mi before the house the dash lights and head lights flashed real bright 3 or 4 different within about 5 min and then the head lights went out but i still had running lights and brake lights just no head lights. the dash lights kept flashing every now and then all the way home. what do ya'll think?

 

Bad voltage regulator causing high voltage that's burning things out?

You have a short somewhere?

Bad grounds?

Is the wiring harness hacked?

 

I had something like that happen before it was the ground that went to the firewall check it

 

It could be either of the above situations.

When the wife's truck shot both NEW headlights at the same time, it was the regulator gone wild.

 

Just an educated guess is that the body to frame ground is loose. It is also possible the alternator to frame ground is not connected as it should be. I know electrical can drive anybody out of their mind, but one of the simplest things to start with is to run temporary ground cables from frame to engine; engine to body; firewall to frame; you get the idea.

 

The body ground on these things suck. If you look on top of the core support above the driver's side headlight, that is the body ground. Yep, a skinny wire out to the rusty core support that's connected to the rusty cab by rusty fenders.

Check the charging voltage first, though. When those regulators fail you wind up with about 18 volts at idle.

 

checked the voltage today and i had about 14.8 at idlei thought that might be to much i changed the regulator and had 15.8-16.2 then the interior light blew. i already made a new ground to the core support with some 4ga wire to the same spot and i checked the ground from battery to block and then to frame it all seemed tight.

 

i found out today that my trucks ecm could be bad or thats what the dealer said about the charging. i called oreillys they want 240.00 for it. what do yall think could it be my ecm?

 

change it over to external regulator shows how in the stickys alan

 

Not on a '91.5. The '91.5 trucks still have the old school regulator on the firewall, the PCM is not involved in the charging system.

Run a ground wire from the regulator case to the engine.

 

well i ran a ground from the regulator to the battery the voltage went down but still around 14.8-15.0 and i tried 3 different regulators and it was about the same voltage with all of them.