1998 mustsge gt heating problem


New Member
Jan 5, 2020
Houston Texas
I just bought a 1998 mustang gt from an auction and it has a few problems. The radiator fan was wire up to a switch because connection plug to the fan was melted and the heat gauge does not work.So I bought a new plug and wired it in and replaced both sending units. The fan will come on when the ac and heater is on but not by it self when it gets hot it won't and the temperature gauge still dont work. I can take the connector off the heat sending unit an the fan will come on but as soon as I put it back on it shuts off. What's next?
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SN Certified Technician
Aug 14, 2009
Houston Texas
For the 1998 model year the dash temperature gauge and the PCM temperature sending unit are separate systems. Trouble shoot each system by itself.

Note, the two temp are NOT compatible to each other other. So expect problems if the incorrect sensor is used or swapped.

To trouble shoot this it would help to know what the PCM "thinks" the ECT temperature is. Do you have an ODB2 scanner? Even better one with bi-directional capabilities?

Here's some information on a very capable Windows based unit.

ForScan ODB2 scanner w ELM327 USB


SN Certified Technician
Aug 14, 2009
Houston Texas
I dont have odb2 scanner. What I have been reading it could be my ccrm. My gauge is a different problem I think
So you don't have $30 for the USB dongle?

The whole idea behind this is to "trouble shoot" the issue so that you are only replacing parts that are actually bad. The CCRM is a rather expensive part to replace on a pure guess. It might be the bad part but without some tests it is just a guess.
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