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Police derigible Art show at the bottom of a pool Stalin's ear… - The Veritable TechNinja [entries|archive|friends|userinfo]
The Veritable TechNinja

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[Jul. 25th, 2002|01:51 pm]
The Veritable TechNinja
[status |tinkery]
[waveform |LSA - Echoes at a Distance]

Police derigible

Art show at the bottom of a pool

Stalin's ear stolen

Butt-eating dog

Cellphone feng-shui

Bored but happy Swiss

Got the resistor pack solution all sorted out and approved by multiple PCB specialists. Going to get two heatsinks that are big enough to cover the board and Dremel out wells in the burface to make clearance for the resistors. To secure them, I'm going to use some Arctic Alumina Epoxy. Fill the wells I drilled with it and slather the rest of the heatsink surface with it, then make a PCB sammich. The epoxy will keep the resistors from shorting to the heatsink, isolate the board from moisture, and hold the heatsinks in place, all while piping heat away from the board. The only hard part will be where to put it when I'm done, but I'm thinking a simple box built around the fans, then screwed down to my floorboard. Might look a bit odd, but it's better than baking in the sun with no A/C. Yay, I get to put on my electrical engineer hat for a while! The guys at the office say I should sell the plans on the internet, that might just be a good idea. If GM sticks this part in most of their recent cars, a lot of people will probably want a solution to this problem.

[User Picture]From: c0nsumer
2002-07-25 12:15 pm (UTC)
Okay, I'm slightly confused. I've been following what you are doing, but I don't quite understand why. Is it that some part in your dash keeps overheating whenever the AC is used and you're going to take drastic steps to be sure that it doesn't overheat?
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[User Picture]From: arcsine
2002-07-25 05:52 pm (UTC)
Yes. It's a high-voltage PCB with surface-mounted carbon rod resistors. It's in-line between the power supply to the fan and the fan speed switch. Depending on setting, it has multiple circuit paths that include various strengths of resistors to restrict a fixed-level output to the fan motor. I'm assuming it carries upwards of 20 amps, as the board got hot enough to burn my finger in less than a second after 15 minutes of use. It's normally mounted in a hard-to-reach place behind the fan motor, in the shroud leading in to the ducts. Problems with that are moisture and ineffective cooling. I plan on isolating it from both with the above. The epoxy will seal the board from moisture, protect the resistors from shunting to the heatsink, and conduct heat away from the board. I'll post pics when it's done.
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