My son has a 94 Accord EX that the left rear brake light only works on occasion, it's really intermittent. We've done the usual stuff...changed bulbs, changed the socket...it usually works when we pull it out and work on it, but we stick socket back into the body and it works fine sometimes for a while and then will quit again. It always tests good with a test light so I know there is power, and the housing of the socket is all plastic so I don't know how it could be a ground issue. All the wiring is in good condition from what I can tell, no cracks, bare spots, bad molex pins or connectors, etc

I've searched the tech forums and haven't found anything like this...doesn't mean it isn't here...I might just not have found it. Also Google'd it to death with no luck. We can't find his Haynes or Chilton manuals and I haven't been able to find a really good, clear, complete, electrical diagram online to see what all is going on in the circuit. Anyone have any ideas or ever seen anything like this before? #$%^'d gremlins!

Any help or suggestions would be appreciated. Thx in advance

 

Issue may be due to either the Brake Light Failure Sensor intermittently providing power/voltage (located and visible near the left brake light socket) or a grounding issue with the black ground wire that goes to the ground bolt, near the left taillight assembly.

Both left and right rear brake lights share the same ground; but, have different wires going to the ground bolt. To examine the ground wires, the plastic panel has to be removed.

 

 

I have a similar problem with my 1990 accord. Iswapped brake light failure sensors. It worked, so i bought a new one for the left side. The new sensor only lasted one day.any ideas? I checked all wiring in trunk area

 

Thx a bunch. I have checked the grounding and it looked like good continuity, but I will take a much closer look now you have given me an idea of a potential trouble spot. I hadn't thought of the failure sensor, probably because every time i pull the plug and hit it with a test probe it shows power to the socket (would make sense that moving the wires around might complete an intermittent ground though). What's the best way to troubleshoot a brake light failure sensor? If I could find a detailed enough electrical diagram, might help a little, especially if it gives a schematic look into the sensor's inner-workings. I would think it's something akin to a relay, closing one circuit if another reads open when power is applied to it.

We bought two accords (minor fender benders on both in the front) to build one good car. We were told they were both 94's, but it wasn't until we towed them home and went back to pick up the titles that we realized one of them was actually a 93. Funny thing is, most parts books references say that 93-94 is kind of a breaking point between interoperability of parts between years, but we have found that a great number of the parts, despite having different part numbers, actually are interchangeable. Maybe I'll pull a sensor from the 93 and see if it makes a difference if after checking the ground closer doesn't remedy the problem.

As I'm writing this up, it dawns on me that we had a similar problem with one of his blinkers in the front bumper, same side. We replaced the plug and and again I checked grounds and occasionally it will decide not to come on...but it works 99% of the time. I'm beginning to wonder if Honda has some "feature" I wasn't aware of dealing with chassis lighting...but I'm pretty sure it's just poor troubleshooting on our part....or there's more to those 93 & 94 parts not interchanging than we thought! Thx for the help.

 

The brake light failure sensors (BLFS) are different between 93 and 94 Accords.

A 94 Accord uses one BLFS for both left, right, and high-mount brake lights.

A 93 uses a separate left BLFS and a right BLFS. 93 Accords have left inner and outer brake lights, and right inner and outer brake lights; unlike a 94 Accord.

They do operate like electromechanical relays, with coils, etc.

 

Even with 94 Accords, there were early production and late production 1994 Accords with different taillight parts (i.e., brake light failure sensor, taillight wire harness (early production 1994 Accords had six wires, late production 1994 Accords had five wire), and left taillight assembly. This is just to let you know you have to careful in getting the correct BLFS part if you decide to replace it.

To check whether you have an early or late production 1994 Accord, look at the 2-P wire harness connector attached to the high-mount brake light. If the wires are Grn/Red and Blk, it is an early production 94 Accord. If the wires are Grn/Wht and Blk, then it is a late production 94 Accord. Let me know which you have, as there are slight differences in the brake light circuit and wiring.

This is part of how the brake light failure sensor works to provide power (+) to the brake lights.
• When you press on the brake pedal, the brake pedal switch applies battery power (+) to the BLFS terminal where the Grn/Wht wire plugs in (terminal no. 1 for early production 94 Accords or terminal no. 4 for late production).
• Ground (-) from G551 goes to the BLFS terminal where the Blk wire plugs in (terminal no. 6 for early production 94 Accords or terminal no. 2 for late production).

Applying battery power (+) and ground (-) should energize several coils inside the brake light failure sensor, which in turn should close several relay contacts to provide power (+) to the different respective brake lights.

You can always open up the BLFS and check the solder joints and components.