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Fuel Gauge problem.

C

csmilne

Member
My fuel gauge in my 1996 C2 993 always shows empty. I have run the car till there was very little fule left in it and measured the resistence across the 2 connectors on the top of the sendor unit. It was showing 0.049 KΩ.

I then added 20 litres of fuel and again checked the resistence across the 2 connectors on the top of the sendor unit. This time the resistance measured 0.032 KΩ.

Can anybody tell me if these readings indicate the sensor is working or is faulty.

Thanks.
 
When this happened to our 964(before we had to sell it-tears),it showed empty all the time-the replacement gauge was the uprated 993 part which then needed the separate electronic adaptor added to it to give a reading at the gauge-it sounds like your electronic bit isn't working (if yours' has one)
 
Could this be the fuel level sender gauge relay? Part number 964.641.081.00. Do you know where it is located and how I can test if it's faulty?
 
Does the gauge needle move at all when the ignition is switched on, even a couple of millimetres?

If not, then it sounds as though there is no voltage being supplied to the gauge unit or the gauge itself is faulty.

Do you have much experience with car electrical equipment and do you have a multimeter? If not, this might be a diagnosis best left to an auto-electrician. However, if you want to do a crude test on the relay, it should make a fairly pronounced click when the ignition is switched to "on" (i.e. to the normal "engine runs" position) - the click should be able to be felt through the body of the relay.

Google came up with some values for 944 fuel level senders at 944 fuel sender info.

MY 77-85
RES 71.6 ohms
1/4 58.7 ohms
1/2 34.5 ohms
3/4 15.3 ohms
1/1 3.2 ohms

MY 85.5-95
RES 63.2 ohms
1/4 42.2 ohms
1/2 21.2 ohms
3/4 8.6 ohms
1/1 2.8 ohms

So it would seem that your sender is working - I don't think they have a mode of failure where they change resistance over time, so the fault probably lies elsewhere.
 
Thanks for the info on resistance etc.

I dont think the gauge moves at all when the car is started.

I have seen diagrams where there is a relay on top of the sender unit, but this is not present on my car. Can you tell me where I can find the relay please.
 
If you look on the 964 forum posts from Marcus (mcgc0)-14.05.12.-6.55-the jpeg shows the electronic sender unit on his fuel tank gauge-this is the 993 upgrade unit which is attached to the gauge with a jubilee clip-as this is a retrofit adaption for the 964 from the 993,the plugs on the harness are the same so if you have no electronic module ,the plug could still be fitted to the gauge without the module but the dashboard gauge will give no reading-this might be your problem,although I don't know whether later 993's had a remote module with the fuel gauge in the dash.
 
There is no 'electronic sender feeder' or 'relay' on top of my sender unit. I take is this is a reference to Part number 964.641.081.00.
There never has been one of these on top of the sendor on the tank and the fuel gauge has worked in the past.
 
Having looked at PET for 964 & 993,I now remember that the electronic module was a temporary fix for the 964 which allowed the use of the new 993 tank gauge & that this module was incorporated in the dash gauge (if I remember what the OPC said at the time) or somewhere close on the 993.
Sorry for misleading you.
 
Thats for clearing that up.

Can anybody else help. If I have established the sendor is working are there any other culprits other than the gauge itself?
 
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