72 521 Headlights and taillight stopped working!!

[Datsunslayr]

ok i am having trouble with my head lights and taillights ... I got them all to work then i started on brake lights and now i cant get my taillights to come on ... this is the wierd part i get 12 volts to both rear tail lights but as soon as i put the bulb in the voltage is dropped and the lgith does not come on and i know they work since they just worked... Am i missing somthing . also the head light rely dont fire but that should not effect the tail lights

 

[datzenmike]

Disconnect the fuse box after noting the wiring and fuse locations. Soak the fuse box in a bath of ordinary vinegar over night. In the morning rinse and dry, instal with NEW fuses. NEW fuses. The vinegar with remove the copper oxide and the fuses will make better connection. New fuses... old ones are not to be trusted by looks.

[Datsunslayr]

ok i got it to work now ... now i need help with flasher circuit ... i flip the switch left or right and i get nothing . how does the circuit work . also thank you ill try that to fix it permently i temp fix it for now ...

[datzenmike]

The vinegar bath will fix problems you didn't know you had. If you had done it over night, you might not have found any problem with the signals. At least half of all electrical problems are chronic fuse and fuse contact. Soak the fuse box tonight and call me in the morning.

 

 

By 'temp fix' you mean good for now but it will crap out in the dark, rain, or 50 miles from home. There is only one good fix and that is permanent.

[Datsunslayr]

I will soak it but i need it done today thats the problem ... I switched the flasher relay with the hazard relay and the right side will flash normal but the left will flash fast or not at all

[wayno]

ok i got it to work now ... now i need help with flasher circuit ... i flip the switch left or right and i get nothing . how does the circuit work . also thank you ill try that to fix it permently i temp fix it for now ...

This is an ongoing issue with the 521, the fuse block gets all temperamental and quits working at the most unwanted moments, like if you hit the brights and now you don't have any headlights except the brights, then if you wiggle the connections on the fuse block and you have headlights again, but no running lights, or more importantly no brake lights.

There is the I just need to get by till I have time to fix it excuse, but that is just an excuse not to do it right, so you cannot get to it today, then don't drive it.

Take the fuse block out and soak it in vinegar for a couple hours then, it's better than doing nothing and having someone rearend you, then saying your brake lights were not working, and it is your fault. 

[ggzilla]

Your flasher is bad. Cleaning the fuse block won't fix that so get a new one. Next one of the left side bulbs is burnt out - one of front, dash or rear bulbs.

[DanielC]

A 521 light circuit.

 

A very common problem with 521 trucks, almost as common as the fusebox issues, is bad grounds on the tail lights.  Run a wire from the tail light frame, to the frame of the truck.  Make sure the frame of the truck is grounded to the engine.  You also need to make sure the ground wires from the alternator frame to the battery, and the voltage regulator mount are still there.

 

The brake light switch is always hot, one one side.  This switch can be on a junction block for the brake lines, in the engine compartment, or on the brake pedal.

 

Get the four way flashers all working before you work on the turn signals.  Sometimes a turn signal flasher will not work unless you have both front and rear turn signals working.