[200q20v] A/C relay jolts ECU, Pops Bose

[Kneale Brownson]

Since it's Labor Day, I decided to Work on the 200q20vt, tackling, among 
other things, locating the A/C compressor clutch relay artfully hidden 
behind the kick panel beneath the instrument cluster.

This is in search of a solution to the problem of the car suddenly 
hesitating and the radio issuing a popping noise when the A/C is turned on, 
or, indeed, when any HVAC setting other than  ECON  or OFF is selected.

Earlier advice from the list indicated I needed to find a relay with the 
part number 443 919 578.   Being the orderly sort, I started pulling the 
visible relays beginning with the lower bank and nearest to the door.   The 
last relay in the upper row bore the # 443 919 578F.   With the engine 
running and the A/C turned on, I could feel that relay click occasionally.

The earlier advice also included a notation that the Audi TSB "fix" for 
this syndrome is to replace the relay with  one numbered  443 919 578E and 
a Zener diode # 443 298 008, and that this $125 parts cost could be avoided 
by replacing a burned diode within the relay with "any Radio Shack 2 amp, 
50 volt or better diode (not Zener)."

Well, the 443 919 578F that I found had no discernible burned diode inside it.

In additional searching, I found a note from Scott Mockry last March that 
there is an "add on zener diode kit 443-298-008 for the A/C compressor 
magnetic clutch wiring harness" for cars earlier than November 1990 and 
with VIN below 024295.  My car was built in July of 1990 and has the VIN 
006235, so I presume the add-on kit is what I need.

Does anyone know whether the kit amounts to a replacement relay I can just 
plug in?  Is this the $125 part?

I'd prefer a $2 diode from Radio Shack, but I can't see where it would go 
on my existing relay.  Does the "F" on the end of my relay part number mean 
I've got the wrong relay to fix with a simple diode?