The Story of My 944 Temperature Gauge

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 Filter box.

Unscrew the clamp to loosen it.

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.

Use a ¾ inch open ended wrench to remove the old sender.  Remember, lefty loosey, righty tighty!

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 max. 

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.

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