brake light electrical help

sdw

Registered User
Problem:

Brake lights aren't working.

So Far:

Checked the hot side of the brake light switch connector have voltage.
Checked the other side of the connector (light green) it has continuity to ground. This doesn't seem right as the resistance of the light bulb should get in the way.

Question:

Do I have a short on the back side of the connector?

tks

sean
 
Don't know.

I bought the car a year ago. When I brought it home the brake lights worked. When I moved it to our new place a couple of months ago they didn't work. (car has never been on the road other than those two days.)

If the bulbs were bad I shouldn't get continuity to ground should I? (all the other lights, blinkers, night time, still work.)

sean
 
..................
Checked the hot side of the brake light switch connector have voltage.
Checked the other side of the connector (light green) it has continuity to ground. This doesn't seem right as the resistance of the light bulb should get in the way.
.....................

I don't see how the light green wire can be at ground potential because this would cause the stop lamps fuse to blow as soon as the brakes are applied (and the brake light switch is closed).
Does the third brake light behind the rear window work?
 
I don't see how the light green wire can be at ground potential because this would cause the stop lamps fuse to blow as soon as the brakes are applied (and the brake light switch is closed).
Does the third brake light behind the rear window work?

I agree, the fuse should blow. But the fuse is good. If I put a jumper across the connector there is no voltage to ground. In my mind the fuse should blow immediately.

If i disconnect the plug to the lights in the trunk I still have continuity to ground on the light green wire of the brake switch connector. I am going to try and trace this wire back and find out where it is grounded unless I am missing something about how this works.

Question:

Can anyone whose brake lights work check the continuity of the brake switch connector (back side of the switch (light green wire)) to ground?

tks sean
 
Checked the other side of the connector (light green) it has continuity to ground. This doesn't seem right as the resistance of the light bulb should get in the way.
The resistance of the lightbulbs is very low (remember you have 4 brake bulbs wired in parallel). This will appear like a short on the wire.

You could remove all 4 bulbs and then check for a short on the wire. If that tests OK, then put the bulbs back in and check for 12V at both terminals of the brake lamp switch while you step on the pedal. If you have no 12V on either side of the switch, then move to testing for 12V at the fuse (again, while you step on the pedal).

Good luck...
 
Thanks for the help. When it stops freakin' raining I will get out there and give it a try!

sean
 
Brake Light Electrical Problem Solved!

Ok. found the problem.

The light green / red wire power wire to the brake switch connector was intermittent. When I checked it for power all was good. but I found if the connector was placed back onto the switch then it might work, might not.

Rewired from the fuse box to the switch and viola brake lights.

I think the continuity to ground was a red herring caused, as Paul said, by the low resistance of the bulbs in the circuit.

Thanks for all the help!

sean
 
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