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A/C Melting the fuse box

Updated 11/04/2004 - Link to Heater Controls Repair FAQ

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Courtesy of Tom Pappenhagen

I thought I'd share a solution to a long running problem on our '81 528i. The symptoms include

  1. the heater blower slowing down in the fourth switch position, and
  2. the fuse holder actually melting and separating so that the fuse lost contact with the holder, resulting in the loss of the blower and a/c.

It had been suggested that the a/c fan needed lubricated (did that), and that the resistor mounted on the aux fan may have gone south (replaced that with a known good one). The problem persisted.

I then attacked the switch itself, removing the switch assembly from the console, the clock and finally the switch itself (it helps to have two spare assemblies to practice on). The switch contacts are pushed against the ring contacts by springs, and the old grease/dirt had rendered one contact immovable, thus the problems.

I disassembled and reassembled the switch, cleaning the contacts, and low and behold, the blower works and the a/c no longer melts the fusebox. The console is a little intimidating the first time, but by the fourth or fifth it's a breeze. Feel free to contact me, Tom Pappenhagen, for more info if you have a similar problem.

An FAQ on how to service the switch assembly is here: Heater Controls Repair


Courtesy of Peter Florance.

Here are two digital camera photos of the fuse box fix. As everyone knows, these fuse boxes melt all the time. I had seen fuse holders hanging out of fusebox, but I really wanted the fuse inside. I used a Dremel tool with a small burr and routed out a rectangular opening to accommodate two blade type fuseholders. A better man would have carefully cut out the holes and glued the holders in. But because it was really hot that day, I just used black RTV silicone (Phenyl Seal might be stronger). I soldered the wires in place in the back. I did this fix last summer and have not replaced a fuse since. I got these fuseholders at Parts America (they have grooves on the sides to mount or join together).


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