I have a wonky temperature gauge on my 1987 Porsche
944. When you first start it up, it
seems to be fine but after driving for awhile, it will start shaking and then
peg itself to the max temp. I’m pretty
sure that is an incorrect reading because the DME would be showing me the big
red exclamation point!
That being said, everything is pointing to some kind of electrical issue, or at least I thought. I have already replaced some of the wiring as well as the electrical connectors that connect to the temperature sender. Still no dice! I had already replaced the transistor on that side of the gauge cluster as well, mostly for the fuel gauge but it was a shared transistor between the two gauges. That did not do it either.
Next item on the list would be the sender itself, so I purchased a new one. This is how you replace it!
Remove the intake air hose.
There are 4 clamps that need to be loosened in order for the
intake hose to come off.
There is one that is keeping the elbow connected to the
One that is connected to the Throttle body.
One keeping the EGR connected.
And one that is connected to the bottom of the elbow, I did
not need to loosen this one, it just popped off.
You will now be able to see the electrical connectors on top of the sender itself. Remove those electrical connectors from the sender and put to the side. Be careful not to damage any of the wiring, or be prepared to replace it.
You should be able to pull the sender out without having to
move anything else out of the way. You
may need to tilt it a little to maneuver it around the throttle body.
Replace the sender with the new one and reassemble.
Unfortunately, this did not solve my issue. At first everything was going fine and then
the gauge shot up to the max level again.
I am now leaning towards there being air in the system. I think that would explain the gauges behavior
and the fact that I thought it was faulty.
What I think is happening is that when the car is cold the sender is
submerged in the coolant. As the car
warms up, the thermostat opens and any air that is in the system gets caught
around the sender which puts the sender in very hot air and pegs it to the
Burping the system is the solution to that. There is a purge valve on what looks like the
thermostat housing that is used to burp the system. I did the best I could to burp it but we’ll
find out if it worked later.
The lesson here is, if you are having a wonky temperature gauge,
properly troubleshoot the issue before throwing parts at it! Lesson learned.