LED rear fog lamps

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flightmaker
Learner - Newbie
Learner - Newbie
Posts: 31
Joined: Fri Sep 26, 2008 5:48 pm
Location: Swindon

LED rear fog lamps

Post by flightmaker »

Is this a common problem? Over the decades the water, salt and other crap thrown up off the road got inside my rear fog lamp units and rotted them from the inside. The right one was still sort of working but the reflector was badly damaged. The reflector on the left one was totally gone and the lamp socket was so corroded that I couldn't even get the bulb out. Something had to be done otherwise it would end up being an MOT failure.

I wanted to keep it looking as original as possible but could not find any commercially available LED units that I could use, so the logical solution was to design my own. See the photos:-

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http://flightmaker.hopto.org/photos/FogLampAssy.jpg" onclick="window.open(this.href);return false;

The square pieces of metal with the plastic screw thread receivers were also getting corroded but still usable so I scrubbed off all the rust with a wire brush and applied Waxoyl liberally.

The white plastic bulb holder/reflector units, I replaced with 10mm thick Delrin sheet. This needs to be 157 x 57mm, with the corners nicely rounded to fit into the plastic bumper inserts, with a 3 x 3mm rebate cut all around the back. You'll see why. A small milling machine is very useful for this. Mounting hole centres to match the original plastic lenses are 135mm apart. If you do end up doing this for yourself, please check that these measurements are the same on your car.

The LED boards are mounted on M3 stainless bolts into blind holes in the Delrin, with plastic spacers to make clearance for the voltage regulators on the back sides of the boards. I cut the wires with the bullet connectors from the original lamp units and extended them. They go through a hole in the Delrin, sealed with epoxy, making sure to get the polarity correct.

The original red plastic lenses have a tab moulded onto them where one of the fixing screws passes through. I removed this, VERY carefully, again using my milling machine. To seal out the weather I used a gasket cut from 5mm thick, closed cell neoprene foam with double sided tape hold the damn stuff in place on the top and bottom edges.

The car has a fresh MOT certificate and the inspector said absolutely nothing about my home made fog lamps.

If anybody here fancies making these, I'm perfectly happy for them to get the bare boards from Newbury Electronics aka The PCB Train, so long as I can arrange for them to be made available, and provide a parts list. Some skill with surface mount assembly and a decent soldering iron is of course required!
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