I have a 5/8 heater hose adapter so I can connect my water temp sending unit. I have it in the heater hose since that is closer to the engine water temp. It will read even if the thermostat isnt' open.
I got mine from e-gauges.com
When I installed an electric fan in a friends f-150 we didn't have time to wait for mail order to get one of those adapters. On his truck I used Black Galvanized pipe (3/4" to 3/4" adapter) and drilled/tapped a hole in it for the sending unit. I then used Copper/Brass 3/4" to 5/8 hose adapters so I could connect the whole mess to the heater hose. For grounding I just put a hose clamp around the entire unit and use the hose clamp to hold a ground wire so the sending unit will work.
The homeade unit is working well and cost $10 in parts. The adapter I got from e-gauges was $35ish. I didn't have to deal with grounding the adapter I got from e-gauges becuase the sending unit on that vehicle was a 2 wire unit. That adapter from e-gauges had a tiny threaded hole that you could bolt the ground wire to. I could have done that with my homemade unit but I all of my taps are tapered so I don't think I could have made a threaded hole work w/out having to drill it too deep.
~Mark
