Check the pin at the towbar plug on the car that is supposed to feed the brake lights,as shown here. Get some one to press the brakes with the ign on,and you should have 12volts at the red(no.6) pin.Sometimes a good clean of the pins is all thats needed,but wiring in the plug is possibly corroded.

Ed

12N_Socket_wiring.GIF
 
Using a bulb for testing is best as a DVM can sometimes give a false reading due to it's very low current draw.
 

Similar threads