Hey everybody, first time poster from Oregon. Picked up my 1996 Cherokee last summer as a camping rig but it has recently become my daily driver. It's always had a bit of an overheating problem but that'll be a different thread. My question now is in regards to the coolant temp sender unit and my idiot light.

I use a scan gauge II for an accurate readout of my coolant temp and know that my Jeep runs at around 202 degrees normally and 222 degrees if I'm in a lot of stop and go traffic (to warm, IMO). I always figured my coolant light didn't work and am only just now getting around to fixing it. I know I don't need it, but it's there so I want it to work.

I removed the bad unit that was in it, part # 56026710 0056 and installed a Duralast TU238. Something still isn't right though. The light is off until my scan gauge II reads about 120 degrees. At that time it turns on very dimly. By the time my engine is at operating temperature, it's so bright that I need sunglasses. Ok, not that bad but basically it gets brighter as the temperature rises.

According to Autozone's website TU238 is the correct part number for a 1996 Jeep Cherokee 4.0L 4WD with a light instead of a gauge but this sure doesn't seem like it is operating correctly. Any suggestions would be appreciated. Thanks guys!

 

You DO know your E-fan should come on at 218*. I'm not sure exactly where the light comes on, but it should be North of there....

 

Yeah the eFan might be part of the overheating problem. It looked new when I bought the Jeep a year ago but I'm not sure if it is turning on when it heats up. In the past three months I've installed a new 195 degree thermostat, water pump, fan clutch, fan shroud ( i broke it into 4 pieces) and one hose going to the heater core. I also did a coolant flush with Prestone SuperFlush. It still overheats when I am stopped at a redlight or in a drive-thru. If I turn the heat on high it quickly drops to below 210 but without the heater on I don't know how hot it would get... I've never let it go above 222ish. But I digress... I'm highjacking my own thread.

I'm wanting to know if anyone else has had issues with getting the correct Coolant Temp Sender Unit to make their idiot light work correctly. Mine is acting as though it is the unit for a gauge because the idiot light gets brighter as the coolant heats up despite the distributors website saying it is the correct part for a vehicle with an idiot light.

 

How old is the radiator? 220+ sounds a little toasty for your area. I presume your ambient temps are still cool so again, 220 seems hot.

 

Looks like that is the proper sender per AZ catalog but you never know with them.

You could pull it and drop it in a pot of water on the stove with your ohmmeter attached, heat it up and see what is happening. However those switch sending units are dirt cheap and I would probably just go to O'Reillys or whoever is handy and get another one.

You didn't ask for our opinion beyond the sender but now that this is your DD I would keep an eye out for a full gauge panel to swap in. One of my happier days when I did this on my '93.

 

I'd bet that ScanGauge II is tellin' the OP truthfully what's going on.....plus a whole lot more.

 

I don't doubt that the ScanGauge is telling the OP what is going on with his motor but he seems to be concerned with what is going on with his temp sender.

 

Howdy DJB. We've had a little heat wave here. Broke 100 year record Thursday. Granted I'm a bit south. Anyway you are the man here, but I'd suggest he just make sure the fan works and take it from there!

No argument with changing the cluster and senders Pelican.

 

That's a sender for the gauge, not the light. The gauge sender does as you describe above. The one for the light acts as a switch- on or off.
Wrong part in the right box isn't that uncommon, nor is wrong part with the right part number stamped on it. Mr W. HungLo wasn't paying attention again.

 

Thanks for the responses guys! I think I will throw the old sending unit back in and exchange it in the hopes that it was put in the wrong box. If that doesn't work then I might try an OEM part or just forget it and do the cluster swap which I may do eventually anyways. For now I'm happy with the scan Gauge which fits nicely in the otherwise unused ashtray (cord is tucked under the dash and ran in behind the ashtray so you can't see it). I have it set to show RPM, coolant temp, volts and intake air temp.

Yesterday I took note that the eFan was on with my Scan Gauge reading 220 degrees. So that's a functioning eFan, new waterpump, new thermostat, new fan clutch and new fan shroud but still getting to warm.

Is my next logical step replacing the radiator or should I look into the head gasket...Or is there something else I should look at? I've got a radiator pressure tester and a compression tester I've been meaning to try out, there is just never enough time.

 

Sounds like the only major cooling system component not replaced is the rad.

 

I just ordered a new radiator from a place called Mac's here in Portland, Or. I'll pick that and a new cap up on Monday. Maybe a couple hoses too.

 

Did you replace the thermostat? If not, be sure to get one from Chrysler

 

I just installed a Duralast failsafe thermostat a couple months ago.