Temperature Gauge Not Working

[pejohnson]

So I recently bought an 89 SHO and have decided to keep it for a while. I have only had the car a couple of months now and do not have much history on it. I have fixed several things but one issue has me stumped. Currently the instrument panel works with the exception of the temperature gauge. Also I have noticed that the fan randomly kicks on typically as soon as you start the car and does not turn off unless you disconnect the battery. It doesn't do this every single time but 9 out of 10 times it kicks on as stated above. One time I went out after letting the car sit for a half an hour and the fan was still on.

I am assuming if I fix the temperature gauge, the fan will read the gauge correctly and fix it self.

Does anyone have an idea of where I should start to check or fix the problem? I have read a few of the temperature gauge threads but only saw to replace the temperature sender. Should I start there?

Thanks.

 

[itwonder]

Gauge sender is located on the back side of the engine block, with a single wire connected to it. It controls only the temp gauge.

 

[projectSHO89]

The temp gauge circuit is separate from the fan control.

For the gauge, check the single wire sensor under the throttle body to see if the wire came off. The sender on the "back" (firewall side) of the engine is for the oil pressure dummy gauge.

The fan problem is probably a bad IRCM module. Check first to make certain the correct module is installed. See the Sticky in the Electronics section for details on the IRCM.

 

[JRA2000TL]

The temp gauge circuit is separate from the fan control.

For the gauge, check the single wire sensor under the throttle body to see if the wire came off. The sender on the "back" (firewall side) of the engine is for the oil pressure dummy gauge.

The fan problem is probably a bad IRCM module. Check first to make certain the correct module is installed. See the Sticky in the Electronics section for details on the IRCM.

X2 on this. My gauge sending unit went bad on my 89 and this was the issue (single wire sensor under the TB). Be careful, when I attempted to remove the metal clip from the wire that attaches to the sensor itself, it broke off. I had to buy a crimp ring, trim back the wire and use the crimp ring to re-attach it to the new sensor. Just the other day, the wire came loose from the crimp, so I'll have to reattach it better. That wire is easy to cut/break so I have very little slack; that's one reason it keeps pulling loose.

 

[Eric VerValin]

Fwiw.. that is a threaded end on that... at least it was. I got a ring terminal on mine and a little nut holding it there..

 

[pejohnson]

Just to follow up on this thread. I installed a new coolant temperature sensor (ie. Advanced Auto Part No. WT386Z) and the temperature gauge is working on the instrument panel. Even better the fan is kicking on and off as it should. I'm pretty excited. It's not too often a project goes that quick, easy and cheap for me. It took about 20 minutes and cost $9.00.

 

[projectSHO89]

If you know how things work, you'd know that something, while it's working now, still isn't fixed.

 

[pejohnson]

I'm not really sure what you're trying to say. I didn't fix the problem? I should have replaced the IRCM? I was planning on driving it tomorrow and see if everything is working. My main concern was driving the car without the temperature gauge. That appears to be fixed, now I'll monitor the temperature and watch to see if the fan kicks on appropriately.

 

[projectSHO89]

Since the fan can operate only when a relay in the ICRM is closed and the gauge sender has zero effect on anything except the gauge....

You likely have a relay in the ICRM that is intermittently sticking.

 

[pejohnson]

Fan still stays on sometimes

So the fan motor stayed on today after driving it. I went back out after 1 hour and it still was running. I took a baseball bat and tapped the IRCM module and sure enough the fan kick off immediately. The fan relay must have been stuck. So does anyone have a type M they want to sell for cheap? Need to give props to 'projectSHO89' for calling this one.

The temp gauge circuit is separate from the fan control.

For the gauge, check the single wire sensor under the throttle body to see if the wire came off. The sender on the "back" (firewall side) of the engine is for the oil pressure dummy gauge.

The fan problem is probably a bad IRCM module. Check first to make certain the correct module is installed. See the Sticky in the Electronics section for details on the IRCM.

 

[jimtash]

The CCRM will also malfunction if it gets wet. Signs of it are a cooling fan that runs and the A/C is on and cycling continuously even though it's off on the climate control panel. If that happens, you need to disconnect the compressor until everything dries as the A/C pressure switch will not work and the whole system will literally get to the point that there is frost build up on it.