I have two radiator temp switches to choose from. Both fit in the radiator.

One sensor is from a 79 635 euro manual and has one pair of leads. This switch is either a 91 or 99 C degree sensor. The second one is from a 78 633 USA automatic and has two pair of leads.

I have determined that the 633 temp sensor is a dual 91 - 106 C degree temp sensor. Each pair has its own power but share a common wire.

As part of our 633 auto to manual swap we used the radiator from the 635 because the 633 radiator included the auto transmission cooling. The 633 is wired for the dual sensor.

Both of the temp sensors measure radiator fluid temp. My question to the forum: what is the 106 C temp related too?

Thanks

I believe the dual sensor may be for a two speed electric aux fan?

Is that the one in front of the air conditioning coils in the nose? I do not have any other electic fans in the 633 engine bay.

Is that the one in front of the air conditioning coils in the nose? I do not have any other electic fans in the 633 engine bay.

Yup, That's the one. It will have a large rectangular resistor mounted on it for the low speed.

Where was the dual sensor located in the radiator, in the bottom? Is there another sensor in the right side of the same radiator? The low temp is usually 91C and the high 99C .... there is something about the 106C that I seem to remember reading about. Let me see if I can find it.

The sensor on both radiators was located in the bottom passenger corner on the back side and just under the hose connection. I will check for the resistor.