cabowally

Hey Guys:
New here and looking for ideas on new one to me.



Got a neighbor that asked me to help him trouble shoot a problem with his right brake light and it’s the damndest thing…


The brake pedal switch tests ok. The left brake light has no issues whatsoever (works every time the pedal is depressed). The problem: "Check Right Brake Light” on the display. The fun/odd part…: when releasing and then depressing the brake pedal, both the right and left lights come on and then the RIGHT light fades out after exactly 3 seconds…every time. The owner said he took it to some electrical guy who said it was a relay and that he checked into it and it was a $300+ part fix, to which I called BS and said no brake light bulb issue could ever be that much…hence why I’m dealing with this—shoulda kept my mouth shut.


The owner’s manual doesn’t talk about any relay that is connected to the brake lights. Fordparts.com does say that there is a $27 Multi-purpose type #12 relay for the r/l turn, stop, and park. I’ve spent 30 mins looking for a relay attached to the rear brake light system and don’t see anything.


I don’t have access to an FSM or wiring diagram so I’m flying blind here. Anyone have any idea what might cause a right brake light lamp to fade out 3 seconds after depressing the brake pedal while the left light stays on and there are no other issue with the car?



THANKS A TON.

cabowally

Completely forgot. This problem is on a 1999 Windstar.

Thanks.

djzx3

I personally would hand check all the wire's leading from the dash to the light. And then if it's not that, then you have narrowed it down to a relay problem or control modular.

__________________
2000 focus wagon 2.0l DOHC Zetec
04 Subaru WRX,:)



How-to directory.

Ford focus DTC codes.

Ford= First on race day.

thefonz

I wouldn't think you would have separate relays for left and right, but who knows these days. Have you pulled the bulb and checked the bulb and socket for corrosion?

cabowally

Completely agree that it's got to be somewhere between the dash and lamp. Just no clue as to where. I can't see anything relay-looking btwn the pedal switch and wiring up into the firewall or in the rear right quarter panel to the light asmbly.

And Fonz. I'm scratching my head why there would be any brake light relay in the first place but spot on a different Left and Right. That makes no sense. Yes, tested the left light socket that works perfectly in the right side wiring and same issue. So, no. Not a connection/corrosion issue.

Bert

There is a relay in the fuse panel. Check your owners manual. It grounds through the rear GEM so if theres power at the bulb and it still dimms, see if the ground is going away. Here are some wiring diagrams. | Repair Guides | Exterior Lighting (1999) | Turn Signal/stop/hazard Lamps | AutoZone.com

__________________
Bert

cabowally

Yup, it's a grounding issue. Power to the socket at 12v on 2 connectors and ground.

What changes is the continuity to ground. Basically it shuts down.

I unplug the rear brake light socket from the connector I then depress the brake pedal I then check continuity between the ground wire of the right brake light wiring and the body of the car: It's 2.3 ohms.
I then plug the socket back into the connector and the bulb comes on for 3-4 seconds and then fades out. Fades, not short or shut off. Dims itself out.
I then re-check ground continuity btwn the plug and ground and it's dived to 65k ohms.

So, for shits and grins I thought I'd just attach the socket ground lead to the body at the back of the car...nothing. still doesn't work.
Also, I swapped the #1 number relay that controls the left brake light (works) with the number 4 (right break light which doesn't) and there is no change.

What ever is responsible for grounding that socket or insuring amps isn’t working. Me thinks.

Thanks a ton for the wiring diagram.

djzx3

Happy to see you got it solved, I personally hate wiring problems, but I've got better over the last 8 years.

__________________
2000 focus wagon 2.0l DOHC Zetec
04 Subaru WRX,:)



How-to directory.

Ford focus DTC codes.

Ford= First on race day.