Just a quick question. The red power lead calls to be hooked up to 12v + . Is this supposed to be switched or un-switched? I can't see the need for the power if the truck is not running. Thanks.

 

When I hooked mine ou on my '02 I hooked it up to full time power (battery). Whoever hooked it up on my '93 hooked it up to the ignition. After having it both ways I prefer full time power. I dont know if there is any pro's / con's either way. just personal prefrence.

 

There is no problem with hooking it up to a constant source. But, like you said, there really is no reason to have a temp reading with the truck off. Mine is hooked to a "key on" accessory circuit.