brake light switch

[1970 521 truck]

My brakes won't turn on and there's new bulbs in them but how to I check the presure switch

[ggzilla]

Easy, just short across the two terminals of the switch. If the lights come on, then the rest of the circuit is fine.

 

If it is like the 1972 521, you will see the switch in the engine compartment, on the firewall.

[DanielC]

Take the two wires off the switch. Connect them with a jumper wire.

Do the brake lights come on? If they do, good possibility you have a bad switch.

 

Another common cause of no brake lights is bad grounds.

The battery grounds to the cylinder head. From the cylinder head should be another black wire going to the alternator frame. At the alternator, there is also another black wire that goes to the voltage regulator, and this wire is on one of the screws that hold the voltage regulator to the inner fender.

The cab is suppose to ground to the frame, as is the bed. Sometimes these grounds go away with the age of the truck,

[banzai510(hainz)]

Does your horn work??? I believe the horn and brak light is on same circut thn its the fuse. ck or clean or put a new fuse.

 

a 72 has the switch underneath the pedal. You can ck but shorting out asGGZilla said or just ck for 12volts on one side thsan push the pedal and 12volts will be on the otherside when it passes thru. or plug and ohm it out and hit the switch. should short.

[1970 521 truck]

Well on the 70 521 the switch is activated by pressure in the brake system right ill check it by trying the by pass method

[kelowg]

but switch may be on pedal assembly, mines a 71 model blt late 70