Temperature sensor misreading?

I broke the temp sensor that sends the signal to the gauge cluster on my 95 gp last week. The dealer wanted 25 bucks for it so I opted for the Napa $10 special. The guy at Napa told me I needed to use thread tape to keep it from leaking..well I did use it though I noted there was none originally.

Anyway the sensor works again now..but it misreads the temp! Now it warms up straight to 250 degrees which I'm sure it's not since everything is cool and running normally. I've had it overheat before this is different. Is it possible the sensor needs to make good contact to the block for an accurate reading? Maybe the thread tape is changing the resistance or something? What do you think? It was a real pain installing...I don't want to uninstall it, remove the tape, reinstall it, just to find it's the same. Am I stuck buying the expensive dealer replacement or what?

thanks in advance.

Remove the sensor and make sure you only got the teflon tape on the threads and not on the sensor. It sounds like that is where the problem exists, something is interfereing with the transmission of heat to the sensor itself. You may want to get another sensor too and make sure it is the right one for your model car just in case this one is damaged you don't have to do the job twice.

Automotive temp sensors must make a good connection with the block to get good readings, if you can find a conductive teflon tape, use it, otherwise go without tape

a little loctite on the threads will help seal it so you dont have to use teflon tape if your worried about it leaking

The threads on that sensor are NPT (national pipe taper) and are self sealing. There is no need to use teflon tape or sealant. If any vehicle sensor requires sealant, it will come from the manufacturer with electrically conductive sealant already on the threads, as required by OEM spec, even if it's an aftermarket sensor.

Just my curiousity - does anyone know where the temp sensor(s) on a 3.1 MPFI would be located?

Thanks,
Kevin

Turns out the "premium" sensor sold to me by Napa was either put in the wrong box from the factory or simply junk. When I went back they didn't have the premium, only the "cheaper" sensor. Well the cheaper sensor worked perfectly.

I noted the premium sensor had a purple wire and no rubber boot to cover the sensor like the factory original. The connector was also difficult to attach.

The cheaper sensor looked identical to the factory original and performs as such in every way.

So watch out if you get a purple one:)

Oh and Richtazz is right, you aren't supposed to use any thread tape. They are self sealing threads.