No Brake Lights

[svca]

Hi, I'm new to the forum and hoping for a little help from some of you gurus. I am helping a friend with his 1969 Austin Healey Sprite. His brake lights have stopped working recently (all the other lights work fine and all fuses are good). In checking the brake light switch, I found no current going to either side of the switch. In further examining the switch, I see that there is a jumper between the two terminals and the only continuity is between the bottom of the plunger and the two terminals when the master cylinder is pushed in by the brake pedal. This to me would indicate a ground is produced instead of the normal switch that supplies voltage to the other terminal. However, the lights seem to be grounded by the housing and housing screws. The brake lights are on the same bulb as the tail lights and I assume it is an 1157 bulb. No current gets to the brake light wire when the brakes are pushed.

What do I need to look for in finding the problem? Thanks in advance.

 

[andrea]

FIRST there are one dedicated to Sprite in this site Spridgets Discuss the Austin Healey Sprite
the presence of a jumper on brake switch can indicate that on the car is applied a mechanical switch or one electrical switch nearest the brake pedal, but I don't know the Sprite electrical wiring diagram

 

[pan]

Yes there is a Sprite section on the forum, but Sprites use the same brake light switch as 'big' Healeys. If there is no current to either terminal then the problem is likely to be a matter of power supply to the switch, not the switch itself.

 

[svca]

Yes there is a Sprite section on the forum, but Sprites use the same brake light switch as 'big' Healeys. If there is no current to either terminal then the problem is likely to be a matter of power supply to the switch, not the switch itself.

These are images of the switch I found on the net. It screws into the side of the master cylinder, not under the dash on the brake pedal. I supplied current to both wires that connect to the switch, but still no brake lights. That's why I think the current must go thru some other module before it gets to the lights, maybe something separating the signal from the turn signals or emergency flashers. I can't find anything about it in the service manual.

 

[svca]

These are images of the switch I found on the net. It screws into the side of the master cylinder, not under the dash on the brake pedal. I supplied current to both wires that connect to the switch, but still no brake lights. That's why I think the current must go thru some other module before it gets to the lights, maybe something separating the signal from the turn signals or emergency flashers. I can't find anything about it in the service manual.

 

[andrea]

I suppose that your friend have a Mk1 Sprite, on this diagram BK SW are number 18on this base you must control the 12V at A3-A4 fuse an the GREEN wire from here to the BK SW !8 --then the GREEN PURPLE wire go to the rear lights- car have Positive ground at origin
you can use a tester or better a lamp test to control the continuity of the wires involved
I hope this helps