Automatic Climate Conrol...Audi 100...1990

[mboucher70 hotmail.com]

That was it...the resistor pack, aka the “a/c blower control unit” on the wiring diagram.

The control head unit is correctly giving zero volts into the resistor pack when the “off” button is pressed.  When the fan is turned on, the voltage reads 10V.
However on the output side of the resistor pack, which connects to the blower motor, the reading remains the same (12V if I recall) regardless of whether the fan is on or off.

Then, measuring the resistance between the terminal that accepts +12V and the output to the fan has zero resistance.  

Thanks to all.   If anyone has one of these to sell, feel free to contact me off-list.

From: Ed Kellock 
Sent: Friday, September 21, 2012 10:46 PM
To: Tony Hoffman 
Cc: quattro at audifans.com ; mboucher70 hotmail.com 
Subject: Re: Automatic Climate Conrol...Audi 100...1990

This issue sounded familiar initially but it wasn't until Tony's mention of the resistor pack in the rain tray that I remembered. I had this same problem on my long-gone 87 5kcstq (haven't typed that in a long time). Anyway, I didn't troubleshoot it specifically, just replaced it, with a used part I believe. 

On Sep 21, 2012 4:51 AM, "Tony Hoffman" <auditony at gmail.com> wrote:

  Start by unplugging the connector going into the fan resistor pack in teh
  raintray area. Test for power there. The bentley will show you which wires
  you are looking to test, let us know what you find.

  Tony

  On Thu, Sep 20, 2012 at 10:56 PM, mboucher70 hotmail.com <
  mboucher70 at hotmail.com> wrote:

  > I removed the climate control unit from the car to bring it inside and
  > examine the PC board.
  >
  > Even after completely removing the control unit, the blower motor still
  > runs on high whenever the ignition is on.  That doesn’t seem like the
  > failure mode of a switch, and thus I’m wondering again if there’s a relay
  > involved.
  >
  > Does the fact that the blower motor continues to run on high even without
  > the control unit, point to it being a likely flaw not related to the
  > climate control unit?
  >
  > I’ve opened up the climate control unit and its quite immaculate and a
  > pretty solid unit.  So before I arrange for a replacement, just wanted to
  > eliminate any other possibilities that would make the blower motor run on
  > high with or without the control unit.
  >
  > From: Jay M
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