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I'm looking to install a new electric fan for my 69'. The temp sensor for turning it on/off needs to be threaded into either the intake or head. My question is, what type of sealant should I use on it, if any. The instructions (yes, I read them) said not to use teflon tape. I assume this allows the sensor to ground itself to the engine. Thanks for any help.
 

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I use ARP thread sealant. It stands up to fuel, anitfreeze and many other fluids that others don't. Much better than teflon tape especially on aluminum and it does not harden, so if you put too much you can wipe off the excess at any time.
 

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I found this on Lectric Limited Inc's web site. They specialize in classic car automotive electrical products.

"Assuming your temperature gauge, temperature sending unit, and wiring is not defective, the most common cause of inoperable or intermittent gauges is the use of Teflon/pipe tape or pipe compound on the sending unit's threads.
Do not use Teflon tape, pipe dope, or any other material on the threads of your sending unit!!! Screw the sending unit right into the engine.

Any material between the threads of the sending unit and the car's ground (engine) can result in your gauge working improperly, or not working at all. Without the sending unit being grounded, your temperature gauge will show an approximate 100 degree reading (pegged to the left, cold side, of the gauge) no matter what the engine's temperature. If your sending gauge is making a poor (high-resistance) ground to the engine because of Teflon tape or pipe thread compound, your gauge will read cooler than the actual engine temperature."

Hope it helps..

Dan
'68 Convertible
 

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Originally posted by dschribs:
Do not use Teflon tape, pipe dope, or any other material on the threads of your sending unit!!! Screw the sending unit right into the engine.
Dan B. is right on about how resistance affects the guage circuit. But I don't know that I'd subscribe to the no-dope theory. It is possible for teflon tape to create a bad connection. I'd say in those cases, the sender isn't installed properly or their is too much tape on the threads.

By design, pipe-thread connections have voids between the threads. Some kind of dope is needed to preventing leaks. Leaking coolant is more likely to create a high resistance cooroded connection. Also, the dope will make the sensor easier to remove in another 30 years.

But back to Dan B's point. It's probably a good idea to take a resistance measurement between the sensor ground and the block to ensure contact is being made. Most likely it will be.
 
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