Was overheating now( Radaitor temps)
cpcycle at earthlink.net
Thu Aug 28 07:03:31 EDT 2003
[ 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.
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 radiator
>thermoswitch should close just above 90C I think. But temperature control
>has no digits!
>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 time
>we've gone over this :) ]
>The MFTS only provides a we're-about-to-overheat signal to the ECU/Climate
>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 current
>from the dash gauge, and sources current(possily from the gauge in the 3-pin
>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 control
>unit and the ECU(via pin #2), and also drives autocheck(pin #4). If you'd
>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 track
>which does not exist in my copy. Obviously the circuit works in the car,
>and the other leg is ground, so #276 must go to the auto-check system, and
>it must be a source. I don't think they would use pin #4 as supply in the
>3-pin version for signalling the ECU+CC, as a low-coolant condition would
>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 sensors,
>you'd find a wax-expansion-driven piston setup, whereby the piston presses
>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 overheating,
>the sensor first tries to save the bacon by cutting A/C and telling the ECU
>to knock off the high-HP shenanigans. Failing that, scream at the driver...
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