Hi guys,

Once again it is time for silly question time:

When I am putting sensors on my engine and around the various spots on my car, so do they need to be grounded (aka. good contact with a grounding point on their bodies), or can they be isolated (aka. teflon tape to seal up). I see most of the sensors and sending units have two wires which I presume are a ground and control voltage coming out of them typically.. I was wondering if any issues will present if I put sealing tape like on the temp sensors or such? Do any of them need a direct connection to offer a ground in other words external to their wires? I see most look like copper or brass in body characteristics, so I just wonder on this point... or is the wiring supplied to them sufficient for all they need?

Looking for opinions and what you guys have done in your cases..

thanks!
mrstan

The fan switch definitely needs to ground to the block... but my experience is that with a thin layer of teflon tape, I've never had a problem with proper grounding.

Off the top of my head, the fan switch and the O₂ sensor are the only ones that shouldn't use teflon tape.

quote Originally posted by Blacktree: ...the fan switch and the O2 sensor are the only ones that shouldn't use teflon tape.

Do you think anyone has ever used teflon tape on an O₂ sensor? Anti-seize FTW.

The temperature gauge switch on the head also requires a ground through the block.

So, it is block temp, O2, and fan switch? I was thinking that any which connect with fluids should be sealed for leaks with Teflon tape (water, oil, gas).

The O2 gets really hot obviously, so this seems like common sense I think.. ;-o.. So do the sensors and probes actually have three connections including the block or frame grounds then along with their two wire connections? Hmm..

You guys are really great by the way in giving your consensus here!!

[This message has been edited by mrstan (edited 01-13-2016).]

The fan switch has a single wire. That should tell you that the return circuit is through the block. The gauge/temp light switch is actually a dual switch. One side for the light is a simple on/off switch. The other side is a potentiometer that varies with temperature. Both are grounded through the engine head. Most sensors have a thread sealer painted on them when they leave the factory. Sensors like the Coolant Temperature Sensor located beneath the thermostat housing, in the end of the lower intake, will use a teflon tape or pipe dope as a seal because their ground is through the wiring harness.

See my Cave, Sensors Quick Ref

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