what does the sending unit on radiator go to it is on the left side 2 wires could it trans fluid temp

 

not sure i understand

 

I have personally never seen a sending unit on an XJ radiator. Unless this is 96+ era XJ thing. I'm not too familiar with them. The only other thing I can think of is the previous owner might have did a homebrew tranny fluid temp. gauge and installed the sending unit there. That was never an OEM option that I know of, though.

 

here is a pic.the reason i thought trans temp was it is on the trans fluid side and the stock gauge you can see the thermostat open and close. i have a 3 gauge aftermarket cluster w/oil pressure amp temp and it dose not flucuate once it gets to about 200 or so.it could just be a bad sending unit causing the stock gauge to move so much.i will disconnect it when it gets warmer(7deg now) and see what stops working.thanks for the replys

 

The only "sender" I can think of that would be physically in the radiator on an XJ would be the Thermal Fan Swtich (TFS) to turn the auxiliary fan on and off on the 1987-1990 XJ w/4.0L I6. It's a fairly large (~7/8" or so) brass bung with two wires.

I'm going to take a leap here and make the assumption that the given applies for you - but it really helps, on questions like this, if you give with at least your model year and engine. As you are probably aware, there were some (fairly significant, in some cases!) changes between the engines used or the model year to the support systems, and that means we have to know what we're dealing with in order to give an answer...

NB: The electric fan on 1991-up is controlled by the ECU, which makes the decision from the CTS installed in the thermostat housing. The "sender" he's talking about disappeared for 1991.

 

sorry forgot pic

 

sorry it is an 88 4.0 all my info is in my signature

 

I learned a long time ago to not assume anything based on a sig or a moniker - you could be talking about a different rig!

From the pic, that's the Thermal Fan Switch for the aux fan.

 

good point thanks