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1990 740 Brake lights

posted by  byOlaf on  Sat Jul 14 21:04 CST 2012
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last visit: Sun Jul 15 08:15 CST 2012
[RELATED]

Car: 1990 Volvo 740
Problem: the brake lights don't light when the brakes are depressed. At first it was the lower lights only then also the center one.
Known Symptoms: Brake lights don't light, bulb warning indicator is lit full time.
Known Working: All other rear lights work. Blinkers, running lights, reverses, Everything but the brake lights. All fuses are fine.

Steps taken so far:
1. My brother tells me he's checked the brake switch on the pedal. I was not there, but I trust that the switch works.

2. Tried disassembling the rear housing. Inside, there's a goofy metal grid used to spread power to each of the bulbs. (Because wires hadn't been invented yet?) There are no char marks or obvious visible gaps in the grid. The tabs beneath the bulbs seem to connect. Switched some bulbs around to check and they all work.

3. Reassembled the rear housings. Googled. Found a common thread online with the Bulb Warning Sensor on these 740's. So I took the bugger out with some difficulty and opened it up. There was a little bit of chipping on one solder (the post beneath 54) and some powdery stuff on the circuit board. Cleaned it all up with an eraser and underneath everything looked fine. All the diodes and resistors and such on the boards look fine. I wanted to set a soldering iron to it just in case but I don't have one here. It looks ok. May simply have been sloppy soldering in the first place?

Any thoughts? I've seen similar issues on this forum, but wanted to get some input on this problem. I think I should replace the Bulb Out Sensor, but I'm not sure. Can't find it for less than 100 locally, can't really opt out.

Also, anyone ever run phantom brake lights alongside? I think it might be easier to simply make new brakelights than to sort out this bizarre mess.

Thanks for any input in advance.
-Olaf
-Olaf





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