[200q20v] A/C Clutch Suppression, was Bose intermittent pops

Bernie Benz b.m.benz at prodigy.net
Thu Jun 14 13:38:27 EDT 2001

We've been here before, Guys.  The inductive energy stored in the clutch
coil is suppressed by a diode in the A/C clutch relay.  If this diode is
shorted, BTDT, the compressor runs all of the time.  If the diode is open,
BTDT, this dissipating stored energy causes the voltage spike upon the relay
opening.  So, you can order and install the the Audi money making fix, or
just replace the diode in the A/C relay.  50V, 2A or better diode, $0.20
from radio shack.


> From: Kneale Brownson <knotnook at traverse.com>
> Date: Thu, 14 Jun 2001 08:45:31 -0400
> To: "TM" <t44tq at mindspring.com>, "Steve Crosbie" <scrosbie at uslink.net>,
> <200q20v at audifans.com>
> Subject: RE: [200q20v] Bose intermittent pops
> At 10:12 PM 06/13/2001 -0400, TM wrote:
>> Steve,
>> I can't remember exactly what the problem was, but there was a TSB issued by
>> Audi
>> regarding a voltage spike when the A/C compressor turned on, which
>> apparently caused
>> a pop in the radio.
>> Maybe you could find it by searching the archives.
>> Taka
> It's really important to fix this problem because every time you hear the
> pop in the speaker, you're also giving the ECU the equivalent of a brain
> electroshock treatment.   After a while, you start getting a violent jerk
> in the engine. The info is on Scott Mockry's site at:
> http://www.teleport.com/~scottmo/elec.html#click
> The harness installs easily into the wiring to the A/C magnetic clutch by
> separating a connection,  plugging in the extra wire and grounding the
> diode.  The relay replaces the A/C clutch relay in the panel below the
> steering wheel.  I got mine last fall from Carlsen for a little over $100,
> I think.  The harness and replacement relay  are dealer-only according to
> the nondealer vendors I contacted last fall.
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