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Erratic Temp Gauge

J

julianm

New member
My temperature gauge seems to be going all over the place recently. Revving the car a little pushes the indicator 3/4 of the way up, and then a couple of minutes later it can go down to 1/4. See the photo below after a 20 minute drive around town. Any ideas what the issue could be? There's plenty of water in the car, so it's not that...

temperature.jpg

 
I've never seen my gauge up that high! Thrash down the motorway in summer and stop in traffic, just gets it about 1/3 way up. But therrmostat and fans cut in consistantly so not overly bothered. Would suggest probably sender or wire. Mike
 
Well, the fan switches on every now and again and there's plenty of liquid, so I don't think anything is really overheating. I suspect it's just the gauge that's faulty, but that's just a guess..
 
I'd guess that this is a bad earth or insufficient isolation manifestation. Mine also has "character", in that the fans switch in later (according to the temp gauge) if the lights are on , than if they're off! As you say, so long as the fans come on & there's some brightish fluid in the expansion tank, it's amusing rather than worrying. I've also fitted an oil temp gauge, so that I have more peace of mind..
 
If the movement is sudden I would suggest an electrical fault, if it takes a couple of minutes to gain temperature I would suggest your water pump is on the way out. Increasing the revs or getting the car above 40mph can help a failing pump keep the temperature down but sitting at idle in traffic will show any weakness in the pump.
 
mine did that - it was accurate, unfortunately the water pump had gone :-(. Hope thats not the case for you.
 
ORIGINAL: julianm My temperature gauge seems to be going all over the place recently. Revving the car a little pushes the indicator 3/4 of the way up, and then a couple of minutes later it can go down to 1/4. See the photo below after a 20 minute drive around town. Any ideas what the issue could be? There's plenty of water in the car, so it's not that...
Click to expand...
Erratic movement of the temperature gauge will probably be as a result of a bad earth or fault with the instrument cluster. I had the same symptoms on a later Turbo. I replaced the instrument cluster and the problem was resolved (easy and cheap to do in a later 944). I've not removed an early instrument cluster - but would be very confident that the fault is something along those lines. Any mechanical issues will cause the gauge to register a change, but much more slowly. Increasing engine revs will increase the voltage across the battery terminals (as the alternator speeds up), because your gauge gas a fault, bad connection or earth problem - it may flick around with a rapid rise in engine revolutions. Regards, Andrew
 
Thanks for all the replies guys. I did another 20 miles around town yesterday, keeping an eye on the temp gauge. It did suddenly go 3/4 of the way up again and then stayed there for the rest of the day. I parked for an hour and when I got back to the car within a minute or two I noticed the temp back at where I left it. Very strange. The other worrying thing is that when I stopped after half an hour of driving, I popped the hood up to discover that the fan at the front wasn't turning, with or without the key in the ignition.
 
Well, the guys at Tower Porsche think it's the temp sensors. They changed the radiator one and the fan now turns as and when it should. Tonight I'm going to get the sensor that controls the temp gauge in the dash fitted, hopefully that'll be the end of my temperature troubles.
 
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