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So far, on factory docs I cannot find any reference to MFTS usage on the AAN engine. Very weird... I'll have to wait until later to look at the Bentley info (which is US specific but usually pretty generic).
I'll remove the confusion on my weeb site. Cheers for spotting this lil anomolie folks.
So far, on factory docs I cannot find any reference to MFTS usage on the AAN engine. Very weird... I'll have to wait until later to look at the Bentley info (which is US specific but usually pretty generic).
Paul
Paul: I developed my AAN pin-out "map" based on the C4 S4 Bentley and VAG143 pages 67 and 68. Not that there can't be errors in either. I know the Bentley has errors regarding the POSs for cylinders 4 and 5.
Good luck sorting the ABY pin 46 issue.
Dave F.
RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant
Popped into local specialists, Bosch's own schematics say that pin 2 of the MFTS connects to both the ABY and ADU's ECU at pin 46 (Thermal Switch)
Also had a look at my ECU connector whilst realigning my newly squeaky glovebox, and pin 46 seems to have a wire coming from it which disappears off into the loom.
@ UrS4boy, you are getting your Mike's and Pauls mixed up .
Thanks for clearing this up, as i have read in numerous posts that the MFTS limits boost on various versions of the blown 20v. But could never find out how it was possible on my AAN when there was clearly no signal going from it to the ECU.
I wonder if the same situation of limiting boost happens at higher temps on the AAN ?
Can you explain why some MFTS's have 4 terminals and mine has 3.
AFAIK - the early 4-pin devices are active in that they rely on 12V supply coming to them, but later ones are passive. Actually I'm a bit fuzzy on this one from memory - try a google on it - I'm sure its covered well on an Audi site somewhere...
Mmmm - SJM's info agrees with my last post on this, but looking at the ABY schematics again I don't think its right. It seems to me that the ground wire is the obvious candidate for deletion so that the device just gets 0V thru the body.
See this is another quandry of mine, have always looked at sensors with the jugment that if it has 3 terminals then 1 must be a set feed say 5 volts, 1 must be a ground or reference ground say 0 volts and the third would be a signal.
OK - I was right 1st time round... The 4-pin MFTS was like this circa 1992 according to Bentley 100/A6/S6 manual.
#1 is T pin which connects to the water temp guage in the cluster
#2 is R pin which is the high temp alarm (more about this later)
#3 is +12V
#4 is C pin which connects to the high temp / low coolant warning bulb
There is an inherent 5th connection by way of grounding the body of the MFTS.
Later schematics show a 3-pin MFTS (plus ground) and the missing item is the 12V feed. I assume the change to 3-pin was a cost saving / reliability measure.
On the AAN engine I cannot see the R-pin connected to the engine ECU on any schematics and there is no reference to it in the Motronic text. So that would be one rather strange bit of change control by Audi across the 20V turbo engines.
The only use of the R-pin on the AAN engine is to signal very high water temp to the aircon system !
Just a thought, but I remember Mihnea telling me that i had an ABY ecu in my S4. If this is the case, is the lack of a signal from the MFTS likely to effect it's running??
'93 S4 Avant now back on the road complete with new shiny go faster bits.
Depends if the ECU hardware pulls that pin up or not. My guess is that it would and if running ABY software this boost control feature would be always OFF running on the AAN loom. If running AAN software then the ECU would just ignore that pin anyway. If you are seeing healthy boost then its fair to say that you are OK.
It would merit a wee investigation with a breakout box to see what goes on at the ECU. I'd actually like to force this condition onto my ABY and see it working - and determine if any fault is stored.
#2 is R pin which is the high temp alarm (more about this later)
On the AAN engine I cannot see the R-pin connected to the engine ECU on any schematics and there is no reference to it in the Motronic text.
The only use of the R-pin on the AAN engine is to signal very high water temp to the aircon system !
Paul
AH! HA!! I sink I may haff founds zee tricks:
If you look at my AAN pin-out Pin 6 is a connection from the Climate Control head to the ECU:
"6-Connection to A/C Control Head –E87- G/Y – likely related to shutting off A/C under wide open throttle (WOT) and/or when the engine is too hot and the extra load from the A/C compressor puts the engine in jeopardy."
So the MFTS communicates with the Climate Control head and the Climate Control head talks to the ECU, so, indirectly the MFTS does talk to the ECU to limit boost at high engine temps.
N'est pas?
RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant
No doubt that pins 6 and 41 at the ECU connect to the climate head-unit (E87) on ABY, AAN or ADU but I have always considered those to be general purpose signals.
None of the docs I have here specifically mention use of pin 6 for the high temp cutoff.
My understanding is that its more to do with the ECU turning OFF the aircon compressor during times of heavy engine load/demand. Page 56 of the AAN self study book says this for pin 6 - "The (aircon) compressor s switched of for a maximum of 12 seconds at a road speed of less than 4mph when the throttle valve is opened quickly."
So I think 'ne pas' is the answer to your question
My understanding is that its more to do with the ECU turning OFF the aircon compressor during times of heavy engine load/demand. Page 56 of the AAN self study book says this for pin 6 - "The (aircon) compressor s switched of for a maximum of 12 seconds at a road speed of less than 4mph when the throttle valve is opened quickly."
So I think 'ne pas' is the answer to your question
My version of VAG143 has a similar quote on Pg. 58, 12 seconds at 7 kph, and 3 seconds in first gear with more that 65 deg of throttle opening. I don't know where I got the Pin 6 = temp info.
And at this point I don't care. I was trying to help but may have just confused the issue (a bit) more. I don't think its resolved for the ABY yet. Bon chance.
RS2'd 93 UrS4 5 spd sedan
94 UrS4 V8 6 spd manual avant
The ABY and ADU are very easy - they make use of the R pin from MFTS which enters the ECU at pin 46. There is a specific test procedure defined for it in the ABY Motronic book.
The fact that its NOT supported on the AAN is the anomolie here. MB, MC, 1B, RR, 3B, ABY and ADU all seem to support it. Zut alors !
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