[LuJac]

My temp guage seldom rises above the first line on the guage. During the summer it would maybe go one neadle width above it after sitting in traffic,ect. Last winter it took way too long to get heat in the car. Just replace thermostate. Now the car heats up quicker, but neadle still goes to frist line, really a little above, before dropping back when thermostat opens. Interior duct temp is 160+. Gas mileage has never been great on this "02 968 Tiptronic compared to the 944S2 I used to use as my daily driver. With my gauge always reading low, how can I tell if it gets dangerously hot ?? My next step is to replace temp sensor at the radiator. The car runs great with no issues, but my low mileage could be related to temp readings to DME. In F2000 series a couple of cars were caught disabling the temp sensors to run richer. How difficult is it to replace DME sensor? Any other suggestions on what to do ?? Thanks for any info.. PFZ

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[rl968]

My temp needle use to run about one notch below half. I replaced the temp switch with a low temp switch over the summer and now it runs one needle above the quarter mark (or first mark) on hot days and won't go above it on cold days. I always thought running the car cooler was a good thing. Can't say anything about how my heat functions as I haven't driven it in cold weather since putting in the new switch.

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[flash]

the gauges are known to be erratic



use a real gauge to determine the coolant temp (like a laser thermometer) - it should be 15 degrees above the thermostat (stock thermostat is 181), or 100 degrees above ambient, whichever is higher



there is such a thing as running too cool

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[chudson]

Others are gonna add to this but the sensor in the radiator is the switch that operates the radiator cooling fans only. The sensor for the fuel injection (DME) computer is in the very front of the engine - easily visible on drivers side front of engine block with a blue connector. The sensor for the dash gauge is yet another sensor with two individual wires located app 5 inches behind FI sensor and in front of knock sensor. I'm quoting as it is on my '93 - I know there is a difference with the hose configuration on 92s.



What is your fuel economy? Post it so it can be compared with others.



What temp is the new thermostat?



What is the actual engine operating temp? - If you have / can find an infared thermometer gun you can get a close reading by checking surface temp close to the hose outlet.



There are ohm specs for the DME temp sensor so it can be tested at specific temps - is it functioning correctly?



Is the fuel pressure regulator controlling pressure corretly? Too much pressure - bad fuel economy.



It is common for heater duct temp to be 20 - 30 degrees lower than engine operating temp.



Hope this helps - others are likely going to have some good info to add also.

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[chudson]

...and as flash stated my gauge shows perfect one minute and pegged to red the next - then back to perfect 1/2 gauge. Something I have got to fix or risk a bad day if it ever tells the truth (about the overheat) and I ignore it!

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[Darryl]

My Cab used to do that normal reading/peg to the top thing and was rectified by North Hollywood Speedo when they repaired some other issues with my instrument cluster. Culprit was a "variable spring loaded resistor" (isn't that a thermistor or something like that) that has a tendency to go bad over time. Not sure if it's a DIY or not but should be, assuming you can find the correct part to replace and are handy soldering small parts. I've got a couple of spare instrument clusters at this point in case you're ever interested.



- Darryl

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[968Syncro]

Darryl,



Thanks for pointing out the problem with the gauge. I have the same problem, the needle can drift to the upper area, short of the red area, at unpredictable times, when I know the coolant isn't very hot (based on experience from the past). I need to get this fixed. I also found that tapping the gauge can cause the needle to drop back down, sometimes where is should be, sometimes just a bit. The symptoms in my case sure sound like the cause is that "variable spring loaded resistor".



Roland

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[chudson]

Yeah, same here for the "whacking" the top of the dash - drops the needle back to normal most of the time. Thanx also for the name of that component. I knew it was something internal in the cluster; now to try and find a source. If anyone finds it before me, shout back. We may have to contact the company that Darryl used. BTW, everything in the name of the part makes sense except for the "spring loaded". This automotive profesional has never heard of such a resistor, but if it fixes my car I don't care what they call it.

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[Darryl]

I may be wrong about the nomenclature and as an electronics professional, you'd think I'd know what they were talking about. At any rate, I too grew very tired of both "whacking my dash" and "tapping my guage". I always thought there was something loose until North Hollywood pointed out the issue. Good luck!



- Darryl

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[anthonymaher]

Seems like an unpredictable/unreliable temp gauge is the rule rather than the exception with the 968. My gauge would read just below red, and fluctuate slightly if I tapped on the cluster. I verified with a laser thermometer that the actual water temp fell within the requirements stated by Flash. My beef is that there are two gauges that I really need to be able to rely on-- the oil pressure gauge and the temp gauge, so even though I was pretty sure the coolant temp was OK, the gauge said it was right at 212 degrees all the time. Therefore I spent too much time looking at the faulty gauge (maybe wondering if it would magically fix itself?).



The best course of action I found was to replace the thermostat (OEM from Pelican, I drilled 6 small holes as described in other posts) along with the temp gauge-- got a used gauge from German Auto Dismantlers for about $50. I will note that there was a slight difference between the original gauge in my '94 968 and the replacement in that there was an additional transistor on the replacement gauge (I wish that I had taken a picture of the two before installing), and now it fluctuates slightly, but generally stays between 8:30 and 9:00. The added bonus is that you can clearly tell when the thermostat opens after about 10 mins of driving and the temp levels off. Before I had no idea what was going on.

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[rickh]

Okay, I'd love to believe this is my problem too! I'm experiencing very similar behavior but for me, instead of tapping the guage, I turn the heater on and the temp drops back down to the 8:30 position. Turn the heater off and back to 10:00. Turning the AC on has little effect. Seems at freeway speeds, it will stay around the 9:00 to 9:30 position. It never goes into the red (thankfully!) but it's hard to relax when the temp guage is all over the place...



I'm going to get a laser thermometer and check the temp values at different times and places. I've change the temp sensor for the fans and they seem to work fine but that was in the garage and the temp guage never went over 9:30... I like other remember the car never running past 8:30...

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[flash]

sounds like air in the system



i presume you've bled it properly (heater on full, fan on, car fully warmed up) and that you have a bleed screw and not a regular screw in there

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[rickh]

Yes, actually we did it at your place too. I have checked it once since then and got a steady stream out. I surely can check it again.

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[flash]

hmmm - i guess we need to put the laser on it and see what's what

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[94SilverCab]

Rick,



You're problem does not sound like the typical "jumping gauge"...sorry to say, it sounds like the symptoms I had just before water pump failed...



<img src="/forum/images/smilies/968/sad.gif" class="smilie" alt="" />



Jay

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