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Subject: Re: HVAC controls not working Author: vtbimmer as Kevin '86 735i VA : member since January, 2004 : 357 posts Posted on: 2004-03-20 16:13:08

I just did this two nights ago..very easy. I wish I had spent the hour and done it when I bought the car.

I don't know if you've ever taken that whole button panel thing out before...but here goes.

Pull out your radio.
There should be two 10mm bolts holding plastic down.
4 screws along top edge.
Reach in through the radio opening, left side, rubber tube. Pull that up, off the metal tube.

Panel should slide out.
Disconnect the wiring harnesses to the A/C controls, along with the OBC connector and the two lights above the rotary knobs.
There are 7 screws holding the Button and Knob boards to the panel, you'll need to get at those, so disconnect whatever you need to pull out those screws. There are two small connections on the bottom of the board, two wires. They are marked with the respective colors. There's a light thats tough to get out, you need to unscrew the two screws that go into the sides of the assembly. You'll see what I mean, then you can pull out the bulb.

Now, take the button panel, should be separate from the rotary knobs, and unscrew the tiny flat head screws that hold the circuit board down. The buttons will pull up, be careful not to lose any springs.

You will see a white rubber cord that goes inside. See how it has those indentations in it? Slide the whole cord about 1/2 an inch to the right, so the buttons push on a fresh section of the cord. See how there's extra on the left, so you can slide it? Cut off the excess on the right end. Everything should line up so the indented sections are where the fresh sections used to be.

Reassemble everything, kinda tricky with those buttons and the springs, took me a few minutes to get it right. It's kind of tricky, and I don't really have any secrets to make it easier. Just don't try to force/break anything.

While you're in there, check the operation of the spring. If you flip the unit over, and take off that circuit board, you will see the spring. Mine was fine, but some collapse. That can also lead to problems. You can replace with a spring from a ballpoint pen, cut to the right length.

It sounds like your microswitch might be acting up as well. You can get a new one from RadioShack, P/N 275-016A . That has a lever on that one, but there should be one next to it without a lever. Only a few bucks. Use a solder sucker to pull out the old switch, and solder in a new one, devising some way to hold the switch to the board.

After doing these things, your board should be good as new.

Whew, did I miss anything?
Kevin Elmore

Kevin Elmore
'86 735i
224,200 miles
Virginia Tech


Keywords: HVAC, pushbutton microswith repair, control panel

• HVAC controls not working - drummertom 2004-03-20 08:07:43 (1167 views)
  • Re: HVAC controls not working - Kevin '86 735i VA 2004-03-20 16:13:08 (4337 views)
  • yes, see www.e38.org/e23/ - DavidC 2004-03-20 09:52:18 (1373 views)
    • That's my write-up...how awesome! (nt) - Kevin '86 735i VA 2004-03-20 12:42:02 (1176 views)
  • Oh Boy! Trial and Error? - ahager 2004-03-20 08:36:54 (1157 views)