One "interesting" (read: Pain-in-the-arsh) fact is the C4 UrS-car water temp gauge is driven by the multifunction temperature switch (MFTS). Sometimes the MFTS fails so you really don't know if the low temp is related to the MFTS or a stuck-open Thermostat. The way to confirm one or the other is to access the
Climate Control Diagnostics and check what the Channel 51 reading is with the heater on. If the gauge reads low and Ch.51 says 89 deg C or so, the MFTS has failed. However, if the gauge reads low and Ch. 51 reads low, e.g. 50 deg C, and you have been driving (or idling) for long enough to warm-up the engine, then the thermostat has failed open and you need to
replace the thermostat.
The F76 Electro Thermoswitch (aka multifunction thermoswitch(MFTS)) is under the intake manifold, as shown in the illustration below:
There are two switches. One is the F98
Coolant pump thermo switch (Item 15 below) for the after run pump (two pin) and the other one (multi-pin (3 or 4)) is the F76 MFTS (Item 16). If you are good, you can do it with out draining the rad and still only lose about 200 mL(or less) of coolant.
PN for the OE 4 pin MFTS is 034 919 369C. The one below is the later three pin (works just fine) available through World Pac:
To change it, you need a 29 mm deep socket (to clear the brown electrical connection) and a stubby rachet. Move the throttle body hose out of the way to get better access.
I changed mine in my Sunday clothes while waiting for my wife to come out of the house to go for Sunday brunch. I was just trialling it to see how I would do it when we came back home and before you know it (about 5 minutes), I had removed the old one and replaced it with the new one. There was some tricky finger work while doing the Dutch-boy dike plugging thing with one finger and handing-off the old one from my right hand to my left hand and then feeding the new one from the left hand to my right hand and then starting the threads by hand. NOTE: All this was done with the engine just warm from getting out of the garage to the street. DON'T DO IT with the engine HOT!!
Note: If the plastic electrical connector in the harness crumbles (due heat aging), the PN for a new one is 893971974
HTH
Dave F.
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