e36 Climate Control Repair

Climate control display dark?

Buttons light up and darken randomly, with button illumination apparently unrelated to what the heater and A/C are actually doing at the moment?

Does it turn off and reset itself randomly?

Your Options:

You could spend about $450 for a new climate control from the dealer.

Or, you could spend about $200 for a used climate control from the junk yard, and hope that it does not fail immediately.

Or, you could send it to the folks who advertise on eBay who will fix it for $40, and be without a heater for a week or more.

Or, you could spend about $1.50 at Radio Shack ($0.75 at Frys) and have it working in about an hour.

 I did this same repair on my other e36 about five years ago, and it is still working just fine.

[image of tools and parts]
Parts and Tools Needed:
  1. Capacitor.  The original capacitor is 0.47 uF.  However, because It is being used as a filter, people who seem to know a lot more than me say that the size does not really matter, and it doesn't even matter if you put a polar capacitor in backwards.   I used a 1.0 uF capacitor in both my e36s because that was what the local Radio Shack had on hand.  The first one was ceramic.  The second one was tantalum.  Both were polar.  From what I read, tantalum capacitors are better.  The first repair is still working fine 5 years later.
  2. Desoldering braid.  It is important to soak up all the solder that is holding in the current capacitor.  If you don't, the molten solder will go down into the hole in the circuit board as you pull the old capacitor off, and you will have a heck of a time clearing that hole so you can insert the new wire.
  3. 30W soldering pencil.
  4. Fine electrical solder.
  5. Small flat blade screwdriver.
  6. Exacto knife or razor blade.
  7. Wire cutters
  8. Needle nosed pliers.
[picture of dash]
Step 1 - Locate your climate control unit in the dash.  If you drive an e36, it should look exactly like this.  If you have the manual control type with the knobs, and it does not look like this, these instructions will not help you.
[removing multifunctoin display]
Step 2 - If your car has a multifunction display, remove all the junk from the storage compartment beneath it.  Now stick your fingers up through the hole in the top of that compartment and pull out your multifunction display.

[remove MFD 2]
There are bumps on the sides, top, and bottom of the multifunction display that keep it in place.  You may find it easier to remove if you insert a flat blade to help them snap out of their recesses.  

[Remove MFD 2]
Also, the flat blade keeps the edge of the vinyl dash cover from catching on the display and tearing loose from the dash as you pull the display out.

[MFD out]
Just let the MFD hang by its wires.  If any of those four bulbs across the top that illuminate the display and clock are burned out, now would be a good time to replace them.  They are about $6 each at the dealer or about $3 each on line.

[pull the CC]
Step 3 - The climate control unit snaps out just like the multifunction display did.

[release CC plug]
Release the latch on the main plug.  The smaller (black) plug just pulls straight out.

[remove fan]
Step 4 - Remove the two screws that secure the fan.  Either a phillips or straight blade screwdriver works on these screws, but a small straight blade works better.  A little canned air cleaned out all the accumulated dust.

[remove screws]
Step 5 - As with the screws that secure the fan, the four screws that secure the face plate are most easily removed with a small straight blade screwdriver.

[unsnap cover]
Step 6 - Remove the face plate.  This side unsnaps with a little help from the small screwdriver.

[squeeze release]
Squeeze the release on the other side with needle-nosed pliers.

[snap off face]
Step 7 - With the face plate off, the front circuit board snaps out easily.  Let it dangle by its wires.

[release board]
Step 8 - Pull out the circuit board.  The circuit board is held in place by a tabs on each end of the board that sticks out from the circuit board and fits into rectangular holes in the plastic case.  How you get it free is up to you.  Just be careful not to bend the circuit board, as it might crack.

[pull board]
Once the tabs are free from their holes, you can pull the board, or push it from the rear using the holes in the back of the case.

[the culprit]
I don't have software handy to make an arrow, but the small blue rectangular object about a half inch from the right edge of the board, right in front of the big blue plug socket, is a 0.47 uF capacitor that has failed and must be replaced.

[scrape varnish]
Step 10 - Scrape off the varnish.  There is varnish on both sides of the board.  The capacitor will be easier to break loose if you scrape the varnish from this side, and you MUST scrape the varnish from the contacts on the back side so you can desolder them.

This picture shows the old blue 0.47 uF capacitor and new gold 1 uF tantalum capacitor.  On the board, the two holes that look silver, just to the left of that tiny surface mount resistor, are the solder contacts for the cap.  I did not desolder these as cleanly I should have.  
This tantalum cap appears to use the same convention as an LED (long lead is positive).  
If you are using a polar capacitor like this one, I have read that the positive side is the side closest to the edge of the board.  That is the way I mounted both of mine, and they both work, but I have also read that polarity does not really matter in this application.

Step 11 - Push the leads from the new capacitor through the holes and solder them neatly.  Then trim off the excess lead.

Here is the finished product - my brand new tantalum capacitor soldered in where the original capacitor used to be. 
Now put everything back where you found it.  This is one of the few jobs where things go back together a lot easier than they came apart.  I hope that your heater and air conditioner work now.  Mine do.