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Dodgy temp. gauge etc.
#1

Well, started with the temp gauge reading high, going to the top mark. I had the whole cooling system checked, also the water pump and radiator are pretty new. Sensor is changed too. Fans work like they should. The car runs fine and does not overheat.



What we found is that the gauge jumps up when the lights and/or fan are turned on and off. Higher when the fan is on 4, with high beams etc. I have cleaned up the ground points I can get to, battery to the chassis, headlights and such. This helped at first, but the problem just comes back, now it just goes to the top mark once the car is warm.



Seems like the oil pressure and voltage could be off also. The speedo, tach and fuel seem the same as always.



Just to add, electricity is not my best subject.
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#2

Me too...I just tap thegauges and they return to normal...oh well...



Jay
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#3

Gauges are typically sensitive to the quality of the grounds. If you have a loose ground wire, it can, for example, cause the gauges to dance around as you drive over bumps. That being said, I've never had the pleasure of troubleshooting a ground problem, so I can't speak to haw difficult of a job it is. It's probably one of those things where you could either get lucky and find it right away, or spend many frustrating hours trying to track it down. If this is the source of your problem, here;s hoping that you will have the former scenario.
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#4

I also have a gauge issue, but the needle is not jumping around, so I do not think that it is a ground, but rather a sender or gauge issue.

I have noticed that over the last few months the fuel gauge does not go to the top when I fill up.

Does anyone know what the voltage to the gauge is supposed to be for 4/4?

Is there a spot in the trunk, under the removable cover over the gas tank, that I could measure the sender output voltage? If so what should it be for full?

Thanks

Brian
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#5

Good question. My fuel gauge has never gone all the way to the top when I filled it up; I just chalked it up to a quirk of the car, but it would be nice if it were fixable.
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#6

Mine does not get quite all the way to the top line of 4/4 either. I chalked it up to a quirk as well.
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#7

Yeah, the previous owner told me it was a common "feature" on all Porsches. Gullible me, I accepted it [Image: unsure.gif]
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#8

I never had the gas gauge problem, But my mechanic fixed the temp gauge. Working fine for three months now. He also fixed the odometer,
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#9

Behind the Gage Cluster are three large connectors. They have upright release tabs that have to be pulled down to release the connectors. There are four football shaped grounds held on with a small nut. Remove the nuts and use a small flat blade screw driver, slide it under and lift up. Clean both sides of the grounds, prongs, terminals and nuts with Electrical Contact Cleaner. You finish cleaning with Q-tips and Alcohol. Clean the three large connectors the same way. If your Instrument Lights are dim, now is the time to freshen them up. Look in the link below and in 3f you will see the football shapes and large conectors.



http://www.clarks-garage.com/shop-manual/body-24.htm



Cheers,

Larry
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#10

Hey, thanks Larry, I will look at those grounding wires. I have to change a light in the instruments, so I can deal with those points at the same time.



Thanks for the replies, I guess it's good to see I'm not the only one with 'issues'. To add, my fuel gauge goes all the way to the top when full, in fact, it stays there for almost 200 kilometers of driving. But it's a bit unreliable, it mostly measures 1/4's at a time, it goes from full to 3/4 to 1/2 to 1/4 without much in between. I judge the fuel needs from the trip odometer.



Anyway, biy these cars sure are fun!



Cheers,

Tore
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#11

Well, I stand corrected - my fuel gauge does go all the way to the top, I guess the fuel pump just shut off early last time. It's squarely on the 4/4 line now.
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#12

I had the same dodgy gauge issue on the coolant side, the gas side always worked. I replaced the gauge over 8 months ago and have not had a problem since
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#13

So it's possible to just change the gauge?



Now that that the outside temp is lower, rainy and cool, the gauge sometimes sits where it should. So it seems to be effected by the air temp also.



It's odd, when I cleaned up the various grounds at various times, it got better, then went bad again.
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#14

Nice informing thread. Regrettably it appears not possible to get out the gauge panel without removing the airbag steer (and thus requiring a dealer reset of the airbag warning light <img src="/forum/images/smilies/968/smile.png" class="smilie" alt="" />). Bummer, I do prefer to manage these kinds of actions myself. Yet indeed, the gauge panel does not fit between the dash top and the steering wheel, apparently.........
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#15

i have the steering wheel out of the white car right now so as to fix the odometer gear. when i get it all back together, i'll let you know if it triggered the airbag light
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#16

You get the airbag light when you reconnect the battery with the airbag disconnected. The airbag can be removed and re-installed without issue if the battery remains disconnected the entire time.
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#17

i have removed the airbag with the battery connected before, and not gotten the light. however, i have made sure the capacitors have had a chance to discharge first.



i have the durametric if i need it, so i'm not worried, but it will be interesting to see what happens
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94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com



"It isn't nearly as expensive to do it right as it is to do it wrong."
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#18

That sounds about right, Flash. If you try to turn the ignition on with the airbag disconnected, that will set the light off. The battery disconnected is just a precaution. By the way. I just ordered my Durametric this week!
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#19

Did this today and there was no corrosion/rust just a loose nut holding the football shaped wedge in place. I used some dielectric grease on the prongs for good mesuare; the gauge seems to be fixed!



As for the air bag light anyone doing the delete may want to test the resistors. The ones I purchased simply conducted the electricity and my light went on, very upsetting when trying to do this correctly.
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#20

Make sure you have a very good meter. Testing at 1-3 Ohms accurately is out of most meters capabilities. People have been using a 3 Ohm resistor but infact the airbag is .66 Ohms. I have a 1 Ohm resistor in place and we will see if it cures the interemittent air bag light some people have when using 3 Ohms. Couple more weeks before it's all back together and ready for summer!
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