I just got an Autometer tranny temp. gauge off my friend. It's brand new but it didn't come with any wire to connect the sending unit to the gauge. In the instructions it says to use 18 gauge wire. I was wondering what length and what kind of wire to buy so it doesn't throw my temp. readings off. Cause the longer the wire, the more resistance; hence, lower temp. readings.. Am I correct? I take it, 18 ga. stranded copper wire is the best? What length/type of wire originally comes with the Autometer temp. gauges?? Thanks for your help...

 

With 18 gauge wire there will be very little resistance.
You could probably run it 50 feet before the temp changes even 5°.

 

Ok thanks... I don't know how sensitive these things are.

 

Some things, like a pyro are more sensitive to wire size, type and length. Not such a big deal with other lower temp type gauges.
I installed a new digetal thermostat with remote sensor in one of our greenhouses a couple weeks ago. When I finally got around to reading the instructions after I was done was surprised to see that the sensor wire could be extended up to 400 feet with 22 gauge wire before the readings would be effected.