Radiator temps -- Ned's comment

Ned Ritchie Q at IntendedAcceleration.com
Sat Aug 30 00:27:18 EDT 2003

1st speed = Engine OFF -- After run
2nd speed = A/C on OR radiator hot
3rd speed = Really hot
            Then AC goes OFF
Be sure to use the Hotter Radiator fan switch, or you really overwork
the fan.

-----Original Message-----
From: 200q20v-admin at audifans.com [mailto:200q20v-admin at audifans.com] On
Behalf Of Chuck Pierce
Sent: Thursday, August 28, 2003 6:04 AM
To: Eugene Kanter
Cc: '200q20v'
Subject: Was overheating now( Radaitor temps)

[ Picked text/plain from multipart/alternative ]
When the radiator fan comes on at idle it is the #2 speed, the low
speed(#1) comes on when the a/c is turned on.
My #2 speed comes on when the needle is almost straight up. Just below
100C. Here is a link to Scott M's page as a reference.
I left my car idling in the 100F day recently with the a/c on and the
car did not go beyond the point where the fan comes on.
I did a lot of work on the cooling system this spring and it seems to
have paid off.

Chuck Pierce
91 200tq 20v Avant about to get Euro lights put in!!!!!!

Eugene Kanter wrote:

>Could anyone tell me when (according to in-dash temperature control)
>radiator fan starts if car left idle for a while? The first stage
>thermoswitch should close just above 90C I think. But temperature
>has no digits!
>-----Original Message-----
>From: 200q20v-admin at audifans.com [mailto:200q20v-admin at audifans.com] On
>Behalf Of Brett Dikeman
>Sent: Monday, August 25, 2003 11:14 PM
>To: Peter Schulz
>Cc: b.benz at charter.net; 200q20v
>Subject: Re: [audi20v] Re: overheating
>>>>From: Peter Schulz <peschulz at cisco.com>
>>>>the ECU and Temp gauge get  temperature information from the
>>>>Multifunction temperature sender ofrMFTS, which is on the left side
>>>>of the engine, below and forward of the distributor
>>>Wrong, Peter.  Neither the MPI nor the Motronic ECUs derive coolent
>>>temp info from the MFTS.  Both use a dedicated sensor located on the
>>>back of the head.
>>At 01:51 PM 8/25/2003 -0700, you wrote:
>>If thats the case why does removing the lead to the MFTS in some cases
>>restore boost (part of diagnosing a bad MFTS)?
>[beats head repeatedly against the wall for this is only the billionth
>we've gone over this :) ]
>The MFTS only provides a we're-about-to-overheat signal to the
>control, a holy-crap-we're-overheating signal to autocheck, and a
>temperature level to the gauge.
>The MFTS sinks current from autocheck to indicate an overheat, sinks
>from the dash gauge, and sources current(possily from the gauge in the
>sensor versions?) for the ECU and CC head.
>The ECU derives exact coolant temperature for purposes of starting and
>timing, from the sensor bernie mentions- the sensor on the back of the
>block.  If said sensor fails/shorts/is disconnected...the ECU assumes
>maximum temperature and sets timing appropriately(I don't recall if
boost is
>also dialed back a little or not, I think it might be.)
>Mike is right- the MFTS sends the overheat signal to the climate
>unit and the ECU(via pin #2), and also drives autocheck(pin #4).  If
>all kindly flip to page 545 in your Bentley repair manuals, you'd see
pin 2
>of the MFTS goes to current track 473(CC head) and 43(ECU).
>Pin 4 is marked as tied to the float switch's supply side(pin #1 on the
>float goes to ground point #82), but supply is marked as track #276- a
>which does not exist in my copy.  Obviously the circuit works in the
>and the other leg is ground, so #276 must go to the auto-check system,
>it must be a source.  I don't think they would use pin #4 as supply in
>3-pin version for signalling the ECU+CC, as a low-coolant condition
>drop the voltage on pin #4 to zero.
>One sidenote- pin #2(ECU/CC overheat signal) triggers earlier than pin
>#4(Autocheck).  If you were to disassemble one of the old-style
>you'd find a wax-expansion-driven piston setup, whereby the piston
>against a spring-loaded canteliever-type deal, relay-style, with two
sets of
>contacts. Playing with the lever, you'll find one set closes sooner
than the
>This of course makes perfect operational sense- if the car's
>the sensor first tries to save the bacon by cutting A/C and telling the
>to knock off the high-HP shenanigans.  Failing that, scream at the
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