i was having problems with mine not coming on all the time as well. Not sure where the temp swith is, or why it isn't working. I ended up just wiring it to come on when the keys turned on. If you decide to go this route then the wire you want to splice into is orange with balck on the bottom of the relay. Some models are gray and black. but again mine was orange

the switch is on the thermostat housing on mine i have the very same problem i replaced the switch it still no come no idea why i got a replacement switch on ebay not sure if you have the same set up being a closed system/older jeep

hmm, you replaced the switch and it didn't help? And it's on the thermostat housing? Man, I guess I missed that... unless it's different on mine. I thought the housing was along side the radiator =\

Guess I have more research to do
Thanks for taking the time to reply!

it need to hit 215 before it will come on then off around 195
so if you are not getting to 215 your not running hot

The elec fan temp sensor is located on the upper right (standing in front of the truck looking at the windshield) of the radiator on a 90. It's a small brass colored unit screwed into the radiator with wires sticking out of it. It's common for it to stop working mine does the same thing. I just put mine on a switch since I wheel mine. It help's ALOT of keep the temp down.

This will solve your prob
http://www.lunghd.com/Tech_Articles/..._Diagnosis.htm

yeah, I'm getting over 215*. It's been running at 220* pretty consistently.
I'm replacing the thermostat and fan clutch on the clutch fan... and I put a new water pump on a few months ago, so that should help with a lot of my coolign issues.

But I wanted to get the fan working correctly too... and I figured the switch would fix that problem at least, if I diagnosed it correctly.

ooh, yes, this is the part I was thinking of! cool, thanks for that.
Where did you get your replacement part? Online? Local store? Is it actually called the electric fan temperature sensor? I thought it was a switch so I'm glad to be told I'm wrong if it helps me replace it

I just looked it up...its call cooling fan switch ....you can get it at auto zone or similar parts store.

Thanks very much Skreed

did you replace the thermostat yet
that should be the first thing for any one with overheat problems

For RENIX (1987-1990 w/AMC engine,) the thermal fan switch for the electric fan is in the driver's side radiator tank - it's a brass bung with a two-wire lead coming off of it.

It makes sense that the fan would work with aircon selected but won't respond to the TFS - the two circuits are parallel, set up in a "Logical OR" fashion.

I believe the replacement sensor is OEMR only.

However, you can use a later (1991-up) thermostat housing and install an adjustable Chevvy switch in its place - the later housings are tapped with a 3/8" NPT port (standard Chevvy temperature sensor size,) and the adjustable switch should be fairly easy to locate in the aftermarket.

OEMR only? (OEMR = OEM, right?)

Hmm, I'll have to check that out. I was looking at this online, thinking it was the right part:
http://shop.oreillyauto.com/ProductD...pe=889&PTSet=A

OEMR = Original Equipment Manufacturer Replacement. Granted, this does also include Crown and Omix-Ada - they're not terribly common, but they carry a lot of parts that the aftermarket does not.

You can probably try Morris 4x4 Center (www.jeep4x4center.com?) for this thing - I know they carry a lot of Crown and O-A parts, because that's where I usually get them.

great, thank you again. I'll check them out now