Dandy observations. Since the fans didn't come on when unplugging the temperature sensor, I would suspect the fan relay module. I have some good used ones here. By the way, did the sensor have two wires? If only one wire, that's for the gauge. You need to unplug the two-wire sensor.
There was a recall for the fan relay bolts breaking off. The relay must be bolted to the core support for cooling because the switching transistor passes full fan motor current so it gets very hot. When they fall off and overheat, the fan motor usually doesn't run, but I have heard of some shorting so the fan runs all the time. A shorted relay gets more than hot enough to burn your hands, (I found out the hard way!), So it might be possible that's what you were smelling getting hot.
Can you tell if the gauge needle is more than 180 degrees higher than "cold"? These gauges are not spring-loaded mechanical units like in the past. They have four coils of wire that are pulsed by the instrument cluster which is a computer module. If the pointer went well over 180 degrees, (I mean half of a full revolution, not temperature), the cluster is trying to pulse it back to "cold" and the shortest way there is to continue going clockwise. If it looks like that's what's happening, the dealer can connect a hand-held computer that will run all the gauges to various positions, then back to their lowest setting. If you want to tackle it yourself, you'll need to remove the plastic cover and physically push the needle back down.
If your gauge only has about a 90 degree sweep, I would suspect a problem in the cluster or something causing the needle to stick. You could try repositioning the needle, then watch what happens when you turn on the ignition switch. If it instantly goes to "hot", unplug the single-wire temp sensor and measure the voltage with the ignition switch on. It should read 5.0 volts on the wire when it's disconnected. If it reads 0 volts, suspect the wire is grounded. If it reads 5.0 volts and the gauge stays on "cold", suspect a shorted sensor. (That would be extremely rare). If you find 5.0 volts on the wire, which you should, and the gauge goes to "hot", the problem in in the cluster. I suppose you could try a different gauge in case one coil is open, but the cluster is the more likely cause.
Friday, April 24th, 2009 AT 3:28 AM