Heater shuts off if headlights are on

Any mods to electronics? Alarms, stereo, etc?

 

I bet it has to do with that aftermarket radio and the dimmer circuit

 

at the engine compartment fuse box there is a shared connector for the headlights and the heater. J9 is grey and it is a 12 position connector that uses only 4 positions. These are the ground connections for both the heater (white/black) and the headlights (red/green).

 

Aftermarket stereo, amp and subs installed before I got the truck. Definitely a poor installation. No alarm system. I will check the dimmer circuit and those fuses and go from there!

 

I would start with the part where everything works when the engine is off but the key is in the "on" position, but not when the engine is running. Seems like there has to be a place in the wiring diagrams where you can find what's different about those two states and troubleshoot them one by one.

As others said, the Toyota complete electrical diagram for your specific truck is the most useful tool for this. Good luck with the gremlins.

 

I'm not the best at tracking down W/H issues, but I took a look at the 2000 diagrams I have. The only thing I saw in common was ground point "IE" that is listed as "near the right hand end of the IP reinforcement bar. Basically behind or above the right hand kick panel area.

 

Wondering if the OP ever figured this out? I'm having the same problem with a tacoma I just bought as well.

 

Do you have your charging system voltage ?

I am guessing your blower motor shuts off when your head lights are turned on??

 

Yup blower motor will turn off when headlights are turned on while running. Oddly enough though when the truck is off (key out) if I flick the lights on, the blower starts and headlights come on

 

Your saying with the engine off the blower motor turns on with the head lights.

Some place you have some crossed wiring either physical damage allowing 2 positive wires to merge without shorting.

After market wiring done rather poor.

Both circuits may share common ground connections loose connections might be the issue.

Most time loose connections will arc and open fuses and more circuits might be effected

One circuit the blower motor is switched power and should not enegrize unless the ignition switch is in run.

Head lights are switched ground

Wish you were close I love a good challenge.

Good luck