Where is it getting the temperature information that calls it? My guess is a bad thermostat, instead of the relay itself. Normally, a temperature sensor, closes when the radiator is above a set temperature, and that sends the call signal to the relay, which closes and runs the fan until the radiator cools off. At which point the sensor opens and cuts of the signal to the relay, which causes it to open and disconnect the fan. So, your relay is probably good and doing what it is supposed to, and whatever is sensing the temperature and telling it to close is bad. The other option is to disconnect the constant hot lead to the relay, and wire it to either an accessory, or ignition hot. I had to rework the fan relay on my sisters Volkswagon Jetta, which was wired to constant hot, and ran anytime the radiator was above 140-degrees. She was spending the summer at my place in Vegas, with a black car. Under hood temps were around 160-degrees, so the fan would run until the battery was dead. I reworded the hot lead to the relay to the accessory circuit hot.
aomorisambar explained it in post # 26 and posted 2 pics of the sensor, quote: ... was able to confirm that is in fact the sensor for the sub-cooling fan. I took some pics with the cover off, you can see it's location just above the muffler. There are three 10mm bolts holding the cover in, and 2 x 10mm bolts holding the sensor support. To test it, I hit it for a few seconds with a heat gun, then turned the key on; sub fan fired right up, and I didn't hear any clicking from the relay. I'm assuming that the engine/muffler was not getting hot enough to trip the sensor, or was getting it borderline which is why the relay was clicking, and the fan turning for a second.
I am experiencing the same problems with my sub cooling fan not coming on. I have checked both the radiator fan fuse and the sub cooling fan fuse and they seem fine. i removed the cover off of the temperature sensor for the sub cooling fan and attempted to hit it with some heat from my heat gun. fan still did not come on. im not sure if i got it hot enough as i did not want to melt anything surrounding the sensor. did you remove the sensor from the bracket when you where testing it? what is the easiest way to check to see if the motor is working and rule that out as a possibility? Thanks all!
I ended up pulling the entire bracket off and giving it a good amount of heat from my heat gun, turned the key to accessory and the fan fired right up. I must just not be getting it warm enough to trip the sensor in the seattle area?
