Possible faulty temp gauge? Hear me out on this...

[XJMark]

I always thought you weren't supposed to use teflon tape or RTV on the threads because it acts as an insulator not permitting the sender to ground properly. The threaded body of the sender is what usually ties it to ground unless this one is different.

Mark

 

[Mestopin]

Haynes manual recommends teflon taping for this particular sender.

 

[Lou]

220 F --> 93.5 Ohms
260 F --> 55.1 Ohms

You definitely want the sensor body to make electrical contact with the head. You might be able to use tape to seal, but I would leave some threads exposed inorder to make contact.

 

[XJMark]

Haynes manual recommends teflon taping for this particular sender.

Wouldn't be the first time a haynes manual was wrong. According to the FSM there are two temp sensors one to the rear of the head for the dash gauge and the one on the thermostat housing for engine control. IIRC the one on the thermo housing supplies its own ground loopback wire so that the computer is reading a correct temp irregardless of the condition of the ground of the thermostat housing, esp. since theres a gasket there. The one for the gauge requires a good ground beacuse it is only one wire to the sensor. I could be wrong though. Trying to find more info in the FSM.

Mark

 

[Mestopin]

I'm fighting a very similar issue as ghettocruiser. The dealer sender doesn't come in until Monday. However all that teflon tape that I applied certainly may explain why I'm getting an odd reading on the gauge (260 with the engine running). Maybe it not getting the proper grounding. Will look into that tomorrow with the aftermarket sender that's in their right now.

Mark
91 XJ 126k

 

[langer1]

I'm fighting a very similar issue as ghettocruiser. The dealer sender doesn't come in until Monday. However all that teflon tape that I applied certainly may explain why I'm getting an odd reading on the gauge (260 with the engine running). Maybe it not getting the proper grounding. Will look into that tomorrow with the aftermarket sender that's in their right now.

Mark
91 XJ 126k

Teflon tape= poor ground= a lower than normal temp reading not a higher reading

 

[Mestopin]

I have so much to learn. Thanks

 

[Oatmeal]

Judging by this photo: http://www.angelfire.com/my/fan/CTS.html the sender dosen't use itself as a ground (there would only be one wire coming out of it), one of the two wires is most likley a ground so, wrapping it with Teflon tape shouldn't affect the values. Just a theory..........Hans EDIT: after thoroughly reading through that link....it dosen't even pertain to the gauge.

 

[langer1]

Judging by this photo: http://www.angelfire.com/my/fan/CTS.html the sender dosen't use itself as a ground (there would only be one wire coming out of it), one of the two wires is most likley a ground so, wrapping it with Teflon tape shouldn't affect the values. Just a theory..........Hans EDIT: after thoroughly reading through that link....it dosen't even pertain to the gauge.

That's the wrong sensor, the one for the gauge has only one wire.

 

[ghettocruiser]

Hey all. Glad to see more joining in on this. I just got back from paragon. Wheeled the snot out of my jeep. I basically said screw the gauge. I knew it wasnt over heating...just wished that gauge was reading correctly to keep my nerves down. I didnt have one issue with heat. No boiling over, no poor running, and certainly no engine failure. I kept turning on the aux. fan just to be safe though.

In any case. I understand the whole not using teflon tape thing. I used it before on that sensor for the gauge and didnt have a problem. Here are my thoughts about the ground. First off the gauge was reading too high. SO that means, according to info on here, that the ground was ok. Now it is reading a lower temp reading. So I can maybe blame the sealer. I took the sensor back out, and cleaned the threads really good. Then I just used a tiny dab of copper rtv near the top. There are definetly threads grounding. I confirmed this with my ohm meter. I tried the sensor with no sealant...but it leaked. And I was afraid to tighten too much...since they arent hard to strip or snap off.

On the trail today..the gauge actually started to read 210. with the fan on just under the 210 line. So I guess it was working for a short bit? Either that or the temp was actually high since the gauge was reading low... Confused as I am yet? Im still not convinced that the gauge isnt faulty. I know the voltage gauge is off...so why not the temp gauge. I really want to grab one out of the yard and try it. If that doesnt work...I might just attact new wires to the back of the cluster. Right onto the screws that make the connection with the gauge. Somehow isolate the stock contacts so they dont interfere.

I dont know... still thinking. I have alittle trail carnage to fix as well as a mud covered engine bay to worry about. Im sure thats good for the wires and sensors...

Justin