I'm working on a D15b in a Mini Cooper. I sent my original harness to a guy and he added the relays and took out what I don't need. The harness tha came back has the water sensor plug that plugs on the thermostat housing but there is no plug for the ECT sensor. Do I not need this now? What does it do differently from the water sensor plug/sensor?

 

The sensor on the thermostat housing is a fan switch. Correct me if I'm wrong someone, but I think the Coolant Temp Sensor is on the distributor side of the head, near the block and is one wire. If you care to have a temp sensor in the dash, I'm pretty sure that's the way to go about it although I have NO clue on the cooper part. Also, I'm not entirely sure how vital it may or may not be to have that information sent to the ECU.

Hopefully I'm not lying to you, but I DO know that the one on the thermo housing IS the fan switch.

 

Ok ok well there is another plug I do have that is for the temp gauge so I think I have that covered. Maybe the ECT is for the ECU input? It's on the other side of the distributor kinda where the transaxle bolts on

 

If it weren't dark, I'd post a pic but yes, I believe we are speaking of the same little guy with 1 round pin sticking out.