Zenner Diode Kit 443 298 008

Bernie Benz b.benz at charter.net
Thu Jul 22 08:51:42 EDT 2004


Yes, The diode at the clutch is absolutely unnecessary.  The system was
originally designed to have the suppression in the relay, not at the clutch.
See the Bentley schematic, Pg. 590.  No diode at the clutch, just in the
relay, that being the diode on current track 487, across the relay contacts.
The afterthought diode kit at the clutch must have been designed to correct
a component failure problem by a summer intern who didn't know what he was
doing nor anything about service cost effectiveness (should have been
selling women's shoes).  I have both the F and the H version relay.  Both
have the diode across the contacts.


> From: Brice2004 at webtv.net (Brice Warnick)
> Date: Thu, 22 Jul 2004 03:12:05 -0500
> To: b.benz at charter.net (Bernie Benz)
> Subject: Re: Zenner Diode Kit 443 298 008
> Bernie,
> So the magnetic clutch coil diode is redundant?
> I am slow learner, so help me to understand. With the newest
> version of the relay,the 578H the Zener magnetic clutch diode is not
> needed or is it not needed after your upgrade to to the newest relay
> version?
> Thanks,
> Brice
> From: Bernie Benz <b.benz at charter.net>
> Date: Wednesday, July 21, 2004 10:38 PM
> To: Brice Warnick <Brice2004 at webtv.net>
> CC: 200q20V mailing list <200q20v at audifans.com>
> Subject: Re: Zenner Diode Kit 443 298 008
> Brice,  Comment below.
>> From: Brice2004 at webtv.net (Brice Warnick)
>> Date: Wed, 21 Jul 2004 19:47:10 -0500
>> To: b.benz at charter.net (Bernie Benz)
>> Subject: Re: Zenner Diode Kit 443 298 008
>> Bernie,
>> I have a bad compressor which is not sucking in R12. At least
>> that is what an expert mechanic told me it was. He was 90% sure the
>> vanes were bad. 
>> So I pulled a 10P17C Nippondeso from my 88 5000 which I
>> planned on fixing someday. I got sideswiped a few years ago in it.
>> Anyway that compressor is good.  Since it is an 88 the magnetic clutch
>> coil does not have the Zener diode attached as this was a 1990 SB. I
>> will most likey pull this diode off of my 20020V clutch coil. I wanted a
>> extra diode kit as I am planning on rebuilding the 200 compressor and
>> clutch. I found a place in Dallas that can do it for $125.00. I want to
>> have a spare compressor as I plan on keeping this car for a long time.
>> I had read that wthout this diode it can cause engine misfiring
>> and idle problems.
>> I am suprised that no one has a cheap alternative to this diode
> I have!  Replace the original supression diode, but only if it is broke!
>> . Not the one in the relay which you have come up with but the one for
>> the magnetic coil.
> They are fuctionally one and the same!  Much easier and cheaper to service
> the one in the relay.
>> The relay is the other replacement part in this SB.
> Just so you understand with certainty, the diode in the AC relay fully
> supresses the the negative voltage spike gernerated by the energy stored
> in the clutch coil inductance, just as effectively as would a diode across
> the coil directly.  The former is also across the clutch coil, but in series
> with the battery, an equally effective and often used method of skinning
> this suppression cat, also a regular Si diode is adequate.  Further, this is
> a poor application for a zener diode, inasmuch as no one cares if the clutch
> requires an additional 50 msec. to release after the relay opens.  So,
> forget and just don't sweat the Diode Kit!
> Bernie
>> Anyway my main problem now is getting ready to remove the
>> compressor from the 20020V. I had a very hard time getting the
>> compressor out of the 5000. I had to end up taking the radiator and
>> condenser out and come in from the top. I think I have it figured right
>> but am still not totally sure.
>> I know that I take the nuts off the bottom bracket first. I
>> cannot remove the bottom bracketbecause the main supporting bracket has
>> a beefy wraparound over this bracket.
>> The top bracket has 2 big 17MM bolts. when these bolts are loosened you
>> can swing the compressor out so that the bottom bracket comes offand you
>> can get the compressor out. My problem is having enough clearance to get
>> to the 17MM that is closest to the radiator.I had to use an 18 inch
>> braker bar to get these bolts off and it was hard to do even from above.
>> I pulled the whole thing from 5000 to examine and those 2 bolts are
>> still in the big bracket. they will not come out but only loosen.
>> Am I doing this right? Is there an easier and more efficient
>> way for removal? I sure in the hell dont want to remove the radiator and
>> condenser on the 200. Maybe this is job that would be easier standing
>> under a lift.
>> Thanks,
>> Brice         
>> PS  Rod Ramsey at TPC and I talked about you today. He is amazed at the
>> fixes you can come up with.  He said that if he had trouble with his 90
>> 90 20V he would call you for a solution.
>> He also said that you do buy stuff from him on occassion.
>> From: Bernie Benz <b.benz at charter.net>
>> Date: Wednesday, July 21, 2004 3:23 PM
>> To: Brice Warnick <Brice2004 at webtv.net>
>> CC: 200q20V mailing list <200q20v at audifans.com>
>> Subject: Re: Zenner Diode Kit 443 298 008
>> Hi Brice,
>> Just wondering how you resolved your AC clutch suppression problem, as
>> apparently you were still looking for the subject kit and fighting
>> compressor and clutch removal after I sent the below message.
>> Bernie
>> Brice,
>> I've never noticed that Bentley shows a suppression diode located on the
>> clutch coil.  I'm sure that my original clutch coil does not have it and it
>> is not necessary if the suppression diode in the clutch relay is good.  Audi
>> must have added this suppression at the coil because of the high failure
>> rate of the diode in the relay.  Forget the coil diode and check the one in
>> the relay, replacing if it is open or shorted, BTDT.  A $0.25 Radio Shack
>> part.
>> Bernie
>>> From: Brice2004 at webtv.net (Brice Warnick)
>>> Date: Tue, 20 Jul 2004 03:39:37 -0500
>>> To: 200q20v at audifans.com
>>> Subject: Zenner Diode Kit 443 298 008
>>> The 88 10P17C compressor I have does not the Zenner diode kit installed,
>>> 443 298 008. It was an SB on 11-90.
>>> I can take the diode off of the 200 compressor.
>>> I figured I would put the 88 compressor on and then send the 200 out to
>>> be rebuilt. I can get this done in Dallas for $125.00 from a former
>>> product manager for Four Seasons who says that that the quality of the
>>> Four Seasons rebuilds in shoddy.  A lot of shops wont even put on
>>> rebuilts anymore because of the poor work. Four Seasons practically
>>> controls the whole market under many different brand names.
>>> Anyway, my question is about the diode kit.
>>> The dealer looked it up for me and they showed only 2 kits in the whole
>>> world and they were in Germany. The dealers cost was $113.42. This is
>>> just for the diode and wire and does not include the relay(443 919 578H)
>>> which I dont need.
>>> Has anyone found another way besides buying this kit? It shows a pic of
>>> it in the Bentley at 87.35 Can you get the diode by buying a rebuilt
>>> clutch or just the magnetic coil with the diode attached?
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