Out of the blue, I'm overheating.  The heater is working fine and blowing hot air (I'm told this is an indication the water pump is probably ok).

Any ideas where to start to trouble-shoot the overheating problem ??   Oh, and I don't recall hearing the fans on (I'll check this tomorrow) so I'm wondering if it may be as simple as replacing the fan switch. 

Any help here greatly appreciated.

Many thanks

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I had a similar problem, and it was the thermostat for the 2nd fan. You can manually activate the fan by turning on the AC, so you may wish to try that. I know it seems counter-intuitive, but when the engine temperature increases above normal, push the AC button. The temp should drop. If it does, your secondary fan is working, but maybe the thermostat isn't. As I recall it's a relatively easy fix.

Anyone have similar experiences?

Yea, I had a very similar experience. The fan died and it seems to take the thermostat with it, so it starts "overheating". My engine never really got "overheated" hot, the usual warm but not hot. I think the thermostat gets "stuck" somehow. The only problem with this is, that the thermostat is located in the middle of the engine, so its not that easy to access. The fan did seem to fail right at about the same time the car started to overheat. I hope this helps. Good luck!

PS-about 3 months after I had all this fixed, the car wouldnt start. I thought it was the fuel pump originally, but then realized it was the simplest fix: the DME relay failed. Simple $25 part and it started right up. I have no idea if this is related but its a good piece of knowledge just in case, or for future reference.
The AC works fine and turns both fans on. When I turn off the AC, both fans stop.

I let the car heat-up, and it went all the way to the point of turning ON the high temp light. Even then the cooling fans did NOT kick in so I'm wondering if it might not be one of the fan switches (but I don't know enough about that circuit to know if that makes sense or not). The heater is working like a champ.
Its possible the fan switch(es) have gone out. I think that is what happened to me. Does the engine get much hotter than usual? (like scalding hot)

Yes the temp gauge pins up hot, and red temp light goes on. Scalding hot, I don't know because I didn't run the car more than a mile once I saw the lights go on. I do know that about a half hour later when I opened the reservoir to check the cooling fluid it was DAMN hot.

You could be correct in that usually when I pull into my garage at the end of a drive the fans are running even after I shut the car off. Now, no fans.

Do you know how many switches there are and where they're located ??
I do not know how many/where they are located. I have to get my repair/reference manual from my workshop tomorrow. I know that my temp gauge said it was hot (and the light was on) but my engine was only warm to the touch, not "unbearable to touch" hot. The thermostat in the engine itself tends to got bad after the fans die. I know that the fans tend to go out between 60 and 70K miles. (on a side note: the first time this happened it was an extremely hot day and I had been driving for a while, just an FYI) I will get my manual tomorrow and repost when I have that information, but the fans are definitely part of (if not) all of the problem. Repost tomorrow with information.
I dont know the number exaclty, but from what I found it looks like there are 2 possibly 3. also try a fuse problem, doubtful but possible
2 switches I think.

It's not the fuses - but good suggestion - unfortunately its seldom as simple as that I guess.

Not having a good plan to trouble-shoot this, and rather than start replacing components one by one, I'm calling my mechanic tomorrow morning. I'm sure he'll sort it all out - let you know the outcome.

Thank you for all the suggestions though Dan. Much appreciated.
Im guessing fan switches and/or thermostat. look forward to hearing the outcome! good luck!
Belt tension, thermostat, radiator leak?
Well, there were two problems that we've found. One was a vacuum switch that needed replacing. That fixed the heater temp and it is working. However, the thermostat is bad (we think) which is why the car is running hot when the heater is on and cooler when the air conditioning is on. I'll know more tomorrow.
Situation resolved - in the end it was the Thermostat.

Thanks to all for your help and suggestions.


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