B20F.

Just above and aft of the Auxiliary Air Valve is the D-Jet temperature sensor.

My engine no longer has D-Jet.

I would like to use this port for an electric fan sensor.

I can find no documentation as to the thread size. The existing sensor (0 280 130 014) is by Bosch. I can find no information from Bosch as to the size of the threads on this sensor.

The threads are parallel, not tapered. There is a small flare at the end of the threads. Seals to the head with a copper washer.

As the sensor is German, they could be metric threads. But I've also learned that they could be BSPP (British Standard Parallel Pipe).

I would really like to find out the thread size. If I could, I could find an adapter so I could install a trigger for the electric fan.

Can someone out there help me... please?

Not metric. I unhelpfully don't know the thread, but it's the same as the oil galley plugs. That's what I used to block off that hole on my carbed E head.

Nope, it's smaller than the galley plugs. Far as I can make out, it's just a 3/8" NF thread. I know I had no trouble finding a suitable plug at a True Value hardware store.

Sorry for the misinfo -- it was a long year ago that I plugged mine.

a better way for a fan switch. get the adapter out of an old saab 900, where the motor's in backwards, not the newer sideways. that pipe is the right diameter for a volvo rad hose and the switch's threads is common to most euro cars. i used a rabbit fan sw that came on at 95c. good luck, chuck.

Exactly! :)

The water in the head is always going to be whatever the thermostat is.

No it's not.
The water in the head will always be hotter than anywhere else in the system as that is where the heat is generated (OK, exhaust ports too but they're in the head as well).
The thermostat (once fully open and water in radiator and remainder of system more or less "balanced") won't make hot water any cooler. i.e. once open and once the water gets hot enough that the radiator can't get it cool and needs fan assistance.
The fan is not needed when the thermostat is closed.

That being said, having the fan sensor in the head will make it come on prematurely and getting a sensor in the return line from the radiator is a MUCH better solution.

Mike!