I removed the radiator in my 1983 Brat to install an A/C condenser from a 1981 wagon. The Brat has an aftermarket sensor to control the fan, and I assumed that was because the fan switch/sensor on the radiator went bad and nobody bothered to replace it. So the idea was to replace that switch but it turns out there are two switches on the radiator and I'm not entirely sure what to do now. One has a single yellow wire coming out of it that was plugged into the harness, and the other has a single connector that wasn't plugged in. The one that isn't plugged in looks like the picture below.

I guess I'm going to just replace the one with the (very frayed) wire coming out of it, but I was wondering if anybody could tell me what the second sensor is. My best guess is the Brat originally came with an AT, and the second sensor has something to do with that?

James

 

I don't know what the second one is but the one you are showing is the fan control. Basically it's a on/off temp sensor that's a ground for the cooling fan wiring.

Make sure your radiator has an earth wire to the body - this ensures a good earth for that switch to work effectively. 

What does the other switch/plug device look like? 

Cheers 

Bennie

Well I verified that the original problem was there is an intermittent connection in the fan connector, which is why they originally bypassed the sensor. Once I fixed that grounding the sensor wire always engages the fan, so I deleted the universal fan sensor/bypass thing. So I guess if the fan still doesn't come in I'll try plugging it into the other one. :-)

The bypass thing has some sort of a sensor zip tied to the radiator hose, a potentiometer to set the threshold, and some wires to connect it all.

 

You can also run an in-cab switched earth wire to trigger the fan if you think the system has no done it’s job. 

Thermo fan should turn on at a touch over half on the temp gauge. 

Cheers 

Bennie