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Temperature Sensor[240-260/87] posted by Jack Paltell on
Wednesday, 29 April 1998, at 4:32 p.m.
For a couple months now I've been fiddling with a temperature
guage in my 87 245 that flip-flps all over the place. First,
I replaced the thermostat. No change. Then, I cleaned all the
connections at the sensor and on the firewall. No change. Fearing
the dreaded wire rot I worried and read all the postings here about wire
wire harnesses. Since all my wires look good and my car is fairly new,
I did not think the harness was the culprit. To test my theory,
I snipped the temperature guage wire at the sensor and patched in a new wire,
thinking this would isolate the problem or fix it. No luck.
The guage still performed erratically. Sometimes dead. Sometimes
halfway. Sometimes a fourth of the way up. Maddening to say the
least.
I noticed as I was connecting the wire to the sensor a few days ago,
that the sensor terminal seemed loose. I could turn the terminal
nearly 360 degrees without the base of the sensor turning at all.
Ah ha, I thought, a cracked temperature sensor.
I ordered the part from RPR for 14 dollars and I'm waiting for
its arrival. Let's hope for two things. First, that I can get
a wrench and my big clumsy hands in there to get the old sensor
out and secondly, that I have correctly diagnosed the problem.
If anybody has done one of these jobs before and can offer a pointer
or two, please send your thoughts.
Jack 87 245 5 speed 220KMILES
Re: Temperature Sensor[240-260/87] posted by abe crombie on
Wednesday, 29 April 1998, at 4:47 p.m.
That is likely a problem as the sensor shouldn't allow motion like that. The other thing that gives wavering temp gauge on 86-93 240's is poor connection of the temp comp board that is part of the gauge circuit internal to instrument cluster. If the sensor replacement doesn't give you stable readings post an inquiry and I'm sure many will be able to give you a hand to repair temp comp board connections.
Re: Temperature Sensor[240-260/87] posted by Don Foster on
Wednesday, 29 April 1998, at 4:48 p.m.
Jack ---
Your problem sounds like an intermittent temperature compensating board. This circuit "linearizes" the response of the temperature sensor signal displayed on the temp gauge. The circuit board is about 1" by 3" and is plugged into the backside of the instrument cluster. After removing the cluster from the dash, you have to disassemble it -- the board is actually mounted inside cluster, behind the main circuit board. It plugs into a socket.
I have replaced several of them. On one, I was successful resoldering the compensating board. On another, I had to get a replacement. I estimate it's about an hour's work, depending on whether you decide to resolder or replace.
Good luck.
Don Foster