Teflon Tape Interferance?

[Clois Harlan]

I recently installed a new Autometer (electric) oil temp gauge and I wrapped the brass adapters with teflon tape. Several people have told me that the teflon tape causes a false reading on your gauge. Has anyone heard of this before?

I may try and and compare my oil temp gauge w/ a reading bounced off my oil pan w/ a laser pyrometer for comparison. I will try not to get snake bit on my arm like I did last time.


Clois

[petek]

If the tape fully insulates the sender from ground then yes, you will get incorrect readings.

I used some of that teflon paste stuff for my temperature senders. Works well to seal the sender and the sender is still well grounded (as measured with a DVM).

[Cobra20646]

Clois,

The only way teflon could affect an electrical gauge is if it acted like insulation between the sender and the block.... i.e. preventing, or causing intermittent ground for the sender.

Some apply really too much teflon tape to the threads. As most threads are tapered and will tighten up securely without the use of tape, too much tape could prevent a metal to metal contact through the tape.

Where is your oil temp sender located in the pan? On my car, there are two drain hole plugs, and I put my mechanical sender bulb in one. I noticed what appeared low oil temps when the car was moving, but rose to a "normal" temp when the car sat still, as in bumper to bumper traffic.... A fellow club member told me to wrap the sender with a few layers of aluminum foil to insulate it. Works like a champ! On your electrical sender, you will have to prevent shorting out the wire terminal, but give this a try to see if it works for you. I was going to try the IR test, but tried this first and never attempted it.

- Jim -

PS I see pete beat me to the "submit" button..

[trularin]

Clois,

There are different ways the sensors operate, ones that have a single lead, generally require good contact with the unit they are mounted into or "grounded" to. These have a problem with teflon tape and some sealants. Literally, you can attach a wire from the sensor to ground and watch a change in meter readings.

The other type, used currently on several vehicles, have a two wire sensor and do NOT require the casing to be grounded. These are NOT affected by teflon tape.

If your sendor has two wires, you are prbably safe to use the tape. If it has a single wire connection, you will probably want to use a conductive sealant or ground wire.

As a last measure, you may want to check with the supplier.

Hope this helps.

Trularin

[Roscoe]

The other way it will interfere is if the excess breaks loose and enters the gauge. I had a fuel pressure gauge on my fuel log and a piece of the excess came off and lodged in one of the primary jets. Not a good thing.

I now use teflon tape for household plumbing and use teflon PASTE for the Cobra.

Roscoe

[Clois Harlan]

Thanks everyone,

I just got off the phone with one of our speed shops and they sell a conductive sealant for this type of application.

Clois

[Chaplin]

Clois, thanks for asking the question. I just installed my oil temp sender (autometer) in my canton oil pan and did use teflon tape. Looks like it will be coming out . . .

I guess teflon paste is the way to go. Learn something new here every day

[Clois Harlan]

I did the very same thing and noticed my temp gauge was reading 150 degrees almost from the get go. I was suspecting some inaccuracy with my gauge. Tonight the teflon tape comes off.

Clois

[petek]

A quick check that you could do to see if the tape is insulating the sender is to put a jumper from ground to the sender's metal body while watching the gauge. If the gauge needle moves when the ground wire is attached, then you've got some excess resistance (i.e. insulation) in the threads of the sender.