turbo coolant hose under the PS pump [now heater valve]

[Bernie Benz]

> From: Kenneth Keith <auditude at gmail.com>
> Date: Mon, 29 Aug 2005 14:38:32 -0700
> To: Bernie Benz <b.benz at charter.net>
> Cc: 200q20V mailing list <200q20v at audifans.com>
> Subject: Re: turbo coolant hose under the PS pump [now heater valve]
> 
> On 8/29/05, Bernie Benz <b.benz at charter.net> wrote:
>> 
>>> From: Kenneth Keith <auditude at gmail.com>
>> <Snip>
>>> The same failure happened back in the day on my '88 5kcstq.  Now I
>>> need a new heater valve.  There is an all-metal one that I found at
>>> Napa, here:
>>> 
>>> http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_res
>>> ul
>>> ts_product_detail.d2w/report?prrfnbr=15568088&prmenbr=5806&usrcommgrpid=6295
>>> 05
>>> 94
>>> .
>>> That one doesn't have what appears to be a water temperature sensor in
>>> it, which my originals had.  I do like the all-metal construction of
>>> that Napa piece, but do I need to get the factory plastic one with the
>>> temp sensor in it?
>> 
>> Bentley is in error in that they label both this DCC (digital climate
>> control) WTS (water temperature sensor) and the ECU WTS as being G62.  Makes
>> trouble shooting very confusing!  They may well be identical sensors, not
>> enough T/R info on the ECU WTS to be able to tell for sure.  But the two
>> circuits have nothing in common.
>> 
>> The DCC WTS' only purpose is to shut off the hot water flow to the heater
>> core when not needed, so it could be located anywhere, and was not used on
>> some earlier models, hot water being on all the time.
>> 
>> Hope this helps, Improvise!
>> 
>> Bernie
> 
> Hi Bernie,
> 
> Thanks for the response.  That system does seems a little ambiguous.
> I was told by my Audi dealer shop foreman friend of mine that the MFTS
> is what is used to measure coolant temp for the climate control
> system.
The MFTS has a lead going to both the ECU and the DCC.  I don't know for
sure what it does but I don't believe that this is an analog temp signal to
either device, maybe a safety shutdown?

>  So, it sounds like I can use the all-metal style without the
> sensor.  Actually, I will maybe test this out and unplug my sensor and
> see what happens.  The heater valve sensor function is redundant to
> the heater flap anyway, right?
If the flap doesn't seal tightly you'll be getting unintended heat.
> 
> I find it almost amazing that they haven't superceded that ridiculous
> plastic valve with something else.  If it had dumped while on the road
> or something, it could have been really bad.  Granted, it is a 15 year
> old part on an almost 200k mile car, and it should have been inspected
> and/or replaced on a schedule, but still!  =)
> 
> Thanks,
> 
> Ken