Q45 brake lights

[DrewQ45]

Yesterday a cop pulled me over. He was very nice about it and informed me that my brake lights minus the center mounted window light are out. He didn't give me a ticket so I appreciate the guy.

I was very surprised as there was no warning on the console display. Anyway, found that one bulb burnt out but switching all four (bad and good) to new 1157 Sylvania LL didn't help. All fuses are all good and contacts also looked okay, none burnt. I have always used Sylvania.

Not asking for help here as the search is my friend. Just wanted to share the resolution from various posts that I compiled into one. Actually, I hope it's the resolution as I haven't actually tried it yet. Just doing my bit to help members.

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"I just fixed this problem tonight on my '93 Q45. The high-mounted light was working, but neither of the other brake lights (left and right taillights). In an area approximately behind the license plate there is a sensor that all of the taillight wiring connects to. You access the sensor from inside the trunk. Remove the plastic expansion bolts that hold the felt trim cover on, and lift the cover up. You will see the sensor, mounted to the sheet metal with a single Phillips screw. Remove the sensor, then separate it from the connector. Inspect the sensor and the connector. On mine, there was "flashover" damage on one of the pins, on the connector side, not on the sensor side. There are either 8 or 10 blade connectors, in two rows. The damaged female connector was in the upper right, if you looked at it head on. There were burn marks in the plastic, and burning coloration on the connector. I cleaned the both the male and female halves of the connector, and compressed the female end slightly to give better "bite" to the blade (male) side of the connector. Once I plugged it back in, all of the brake lights worked. I don't know what caused the original damage, so I don't know if this is a permanent fix or not. BTW, I found the wiring diagrams in the full owner's manual, the one that comes in the trunk (in its own cubby above the spare tire)."--------------------------------------------------------------------------------------------

"K...I think I may have found it...along the rear side of the tunk inside near the trunk latch release. And I did notice that when i pulled it out, the third light won't work. Is there a way to check it? K...disregard...fixed it...I tend to do this a bunch... Took the sensor apart and found that a couple of the soldered joints had broken lose. Resoldered and I've got lights...Maybe that'll help someone someday..."---------------------------------------------------------------------------------------------

"just went through this with my partners 90Q. It is probably the brake lite sensor. It is about 80 bucks. It is located in the trunkand is mounted on the rear panel, right on the other side of the license plate, and below the trunk latch. Take off the liftover trim, which allows you to move the carpetted panel away from the trunk wall. You will see a green or black box about 5"X3"X1" with a plug at one end. On my partners there was a visible brown melted area. I did not know they use this sensor for the brake lits until I went over the wiring diagram. But that is probably the culprit. I don't know if one going bad denotes a problem somewhere else in the wiring, but my partners has been fine since we replaced it. So maybe they just have a service life and go bad on their own."------------------------------------------------------------------------------------------

"New assemblies are prudent with age IMO. The sensor is a DIY job. Unscrew and pop off the plastic trunk lip trim, remove the rear carpeted panel (plastic fasteners), and the sensor's screwed on right behind the panel. Go ahead and get to it after putting in the new assemblies, then tap it hard and jiggle the harnesses on it before you order a new one. What the heck, it won't hurt."----------------------------------------------------------------------------------------

...Drew...

[hannibal]

Interesting info. I cant believe a bad brake light sensor keeps the lights from working. Seems like a minor engineering design flaw.

[DrewQ45]

Interesting info. I cant believe a bad brake light sensor keeps the lights from working. Seems like a minor engineering design flaw.

Yeah... it actually turned out to be the problem. Close scrutinization revealed a cracked solder joint which I resoldered. Good as new since then. (Talk about a late reply... )

[Q45tech]

Things that exceed 7 years or 100,000 miles are engineering design flaws in the minds of company accountants and excecutives.

[qship96]

Things that exceed 7 years or 100,000 miles are engineering design flaws in the minds of company accountants and excecutives.

It is exactly this thinking that killed the American auto industry,lets hope it doesnt infect the Japanese

[AlabamaDan]

I agree. I'd really like my Q be my car in another 20 years.