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993 oil temperature gauge fluctuating

 
Old 06-22-2009, 10:29 AM
  #1  
gergoid
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Default 993 oil temperature gauge fluctuating

I have a 1996 993 cab, very standard, no modifications at all, 58k on the clock.
Most of the time the temperature gauge behaves itself. Usually doesn't go too
much above 9 o'clock, and only then on hot days.

But occasionally (say once every couple of months) the temperature gauge
will start fluctuating wildly. It starts out normal, as the engine warms up the
gauge slowly rises to the 8 o'clock notch. And then it will start to climb and
dip quickly, as in a jumping around from 9 o'clock to 10 o'clock and back
in under a second, continuously. Nothing seems to bring it back to normality
while the engine is still running. All the time the oil pressure readings are
completely normal. Its jumps aren't consistent either, it just seems to jump
around all over the gauge, mostly in the upper half (often jumping into the
red).

I often check the oil level, and it always seems fine - not low on oil or anything
like that.

For the last 2 services at the Porsche dealer over the last 2 years I have asked
them about it and to check the oil gauge and sensor, and they say they
can't find anything wrong. Of course the problem never happens when the
car is in the work shop!

Does anybody have any idea on what could be wrong?
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Old 06-22-2009, 12:06 PM
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BobbyT
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Obviously, the oil temperature isn't changing that quickly. It sounds like a loose connection or short somewhere in the oil temperature wiring circuit. The first thing I would check is that the connections at the sender and on the back of the gauge are clean and tight.
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Old 06-22-2009, 12:29 PM
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I had a similar problem with my '96 C2 a couple years ago. I bought a used gauge from a rennlister (for short $ I might add) and problem went away. Good idea to check connections 1st as mentioned above.
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Old 03-02-2016, 09:11 AM
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Resurrecting an old thread here because I have just tried to put right a similar problem and couldn't find much guidance other than to send off the gauge for repair.

On my '94 C2 the temp gauge would rise steadily and then jump into the red suddenly. Usually tapping the dial would bring it straight back down, so it seemed that it was a fault with the gauge itself or the connection rather than the thermostat or high oil temps.

I removed the gauge from the dash and then unscrewed the 4 screws from the back to look inside. I found that around the solder joints and the contact points for the connection there was a lot of deposit built up. I removed this carefully with a flathead screw driver trying not to scratch the main surface.

I have taken the car out once since this, but so far seems to have solved the issue. Would be interested to know if others have experienced the same thing.
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Old 03-03-2016, 02:48 AM
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Hi Henry,
I had an intermittent problem with the oil pressure gauge...so made a small project out of it.
Have a read at this thread http://forum.porsche-club-ireland.co...72844#msg72844
Use of contact cleaner is the short executive summary on my project.

Edit:
see thread https://rennlist.com/forums/993-foru...t-stopper.html as well
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Old 03-03-2016, 09:02 AM
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Mine has done the same thing for years. Some time ago my mechanic resoldered the contacts in the gauge which fixed the problem for a while.
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Old 03-03-2016, 09:28 AM
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Thanks guys. With that one settled it has got me thinking about checking the fan is operating correctly as a next step.
Excellent little write up to be found here for those interested -

http://p-car.com/diy/fan/
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Old 03-03-2016, 11:02 AM
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Originally Posted by 993c4ie View Post
Use of contact cleaner is the short executive summary on my project.
Hmmm...I'd be REALLY careful using any kind of spray when working on a gauge. I can only imagine the hassle of trying to clean contact cleaner residue off the gauge face or the glass...without leaving some kind of marks/residue.
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Old 03-03-2016, 11:53 AM
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Apply cleaner with small hard brush or tooth brush to the pin and connector only. Don't soak the unit / don't open the unit.
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Old 03-03-2016, 06:00 PM
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Had a similar problem. Sent unit to North Hollywood Speedometer and they replaced a defective meter movement, refurbished and calibrated. Unit works as it should and the cost was reasonable. Very satisfied.
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Old 03-05-2016, 07:42 PM
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Originally Posted by henrybr View Post
Resurrecting an old thread here because I have just tried to put right a similar problem and couldn't find much guidance other than to send off the gauge for repair.

On my '94 C2 the temp gauge would rise steadily and then jump into the red suddenly. Usually tapping the dial would bring it straight back down, so it seemed that it was a fault with the gauge itself or the connection rather than the thermostat or high oil temps.

I removed the gauge from the dash and then unscrewed the 4 screws from the back to look inside. I found that around the solder joints and the contact points for the connection there was a lot of deposit built up. I removed this carefully with a flathead screw driver trying not to scratch the main surface.

I have taken the car out once since this, but so far seems to have solved the issue. Would be interested to know if others have experienced the same thing.
Is the back plate just secured by the 4 screws? I removed them and even with sone prying, it appears to be attached somewhere else. Your guidance would be much appreciated.
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Old 03-07-2016, 05:21 AM
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Normally , yes....but sometimes solder is applied to the 2 pins (square-ish, at 12 and 6 o'clock relative to the yellow bulb holders) to sort out a bad connection ) as it is the case on your unit).
So desolder these and you'll be abl to pry the plate out.
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Old 03-07-2016, 12:52 PM
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Originally Posted by 993c4ie View Post
Normally , yes....but sometimes solder is applied to the 2 pins (square-ish, at 12 and 6 o'clock relative to the yellow bulb holders) to sort out a bad connection ) as it is the case on your unit).
So desolder these and you'll be abl to pry the plate out.
If I desolder, I need to solder again, correct? Can it be easily done? Does this mean that someone already worked on it in the past?

Do you have any pics of how the backside of the board looks like? I am just wrestling with trying it myself vs. sending it out.

Sorry for Qs but it might serve as a good reference for user users in the future.
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Old 03-08-2016, 06:06 AM
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Can you read/access this thread http://forum.porsche-club-ireland.co...72844#msg72844 on Porsche Club Ireland forum?

if not, pm me your email adress and i'll send out photos..
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Old 03-08-2016, 09:00 AM
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I too, am interested in seeing your photos. You have to be a member of the Irish club, but they don't seem too responsive to requests to join...
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