I am surprised no one knows where the MTFS is
 

This Multi function Temperature sensor is what may be causing my A/C not working and my coolant warning light flashing....will a caring soul that has a service manual, please tell me where this aparatus is?

thanks

"Multiple Failure Sensor" location
 

On my 96 A6, the "Multiple Failure Sensor" is located on the passenger side of the black air box at the rear of the engine below the hose clamp that connects the engine-side air intake tube and in front of the row of connectors that are on the firewall. As far as I know, that sensor only used for supplying the temperature to the temperature gauge and fuel injection computer.

The sensor that makes the coolant warning light turn on is located in the coolant expansion tank on the driver's site where you put the water in.

Neither should have any affect on the A/C. If the cooling fans are not working, then the pressure gets too high and the high pressure switch cuts off the compressor. The compressor won't run if the low pressure switch (under the drip cover) is not connected.

If you have the digital climate control A/C, have you checked for OBD errors?

Re: "Multiple Failure Sensor" location
 

thanks for the quick reply.

The cooling fans are running fine, actually they engage when the temperature gauge gets past 12 o'clock, then the gauge remains normal for about 5 minutes then the gauge raises and the cooling fan starts again, this process takes over and over.

I saw the sensor underneath the coolant reservoir, unplugged it and plug it back, still same problem.

I run some OBD, this is what I get:

Code 1 System malfunction - displayed as a Diagnostic Trouble Code (DTC)= 05.3 and 18.3 it goes back and forth to these values


Code 2 Digital value of Interior Temperature Sensor, in Headliner (G 86) = 09.4

Code 3 Digital value of Interior Temperature Sensor, in Instrument Panel (G 56) = 10.5

Code 4 Digital value of Fresh Air Intake Duct Temperature Sensor (G 89) = 07.3

Code 5 Digital value of Outside Air (Ambient) Temperature Sensor (G 17), front = 07.0

Code 6 Digital value of Outside Air (Ambient) Temperature Sensor = 25.5

Code 20 A/C Compressor (A/C Clutch) voltage (Volts) = 14.2


code 26 Analog/Digital value, Engine Coolant Temperature (ECT) Warning Light = 00.1

Is there a specific code i need to look at?

thanks

You right !
 

<center><img src="http://pictureposter.audiworld.com/85015/multiple_sensor.jpg"></center><p>

Re: "Multiple Failure Sensor" location
 

I found a site that lists the DTCs for the A/C system. Even though the page refers to "early 90's" models, I beleive that the '96 models are included.

http://www.audifans.com/twiki/bin/view/Audi/HVACDiagnosticCodes

According to that page:

05.3 = Outside Air (Ambient) Temperature Sensor, front, sporadic open
18.3 = Fresh Air Blower voltage, sporadic

I don't know whether or not those errors will prevent the A/C from working.

I also don't know if those errors will clear themselves or how to clear them.

Do you have the Climate Control or are you using a Scan Tool?
If you have Climate Control, does the snowflake turn on when you try to turn on the A/C?

David

it was the Coolant Temperature Switch (BINGO)
 

I finally took the car to an Audi mechanic, he quickly found out that the Coolant Temperature Switch was defective, he changed it and it fixed both problems.....The A/C and the Coolant light warning light.

It cost me $180.....kind of high, he charged me $80 for the sensor and $100 for labor.....the switch cost $42 at https://www.autohausaz.com/catalog/lookup_parts.cfm?SubcategoryID=4308&amp;VehicleID= 1008841&amp;CFID=418684&amp;CFToken=82754322

in any case, the car is running again and I want to thank DMW96A6 and OA 69 for going out of their way to help me out.....all this troubleshooting helped me get to know my Audi better, hopefully it will be ok for awhile.

This is an awesome site, lot's of good info

Rgds,

It is "MFTS" Multi Function Thermal Switch
 

<center><img src="http://pictureposter.audiworld.com/85015/multi_function_thermal_switch.jpg"></center><p>

Re: It is "MFTS" Multi Function Thermal Switch
 

Yes, you are right, but I guess we are talking about the same part but different name (for others).

Thanks for following up