arluk3

The schematic suggests that the blue wire at the radiator fan relay goes directly to the thermosensor, and that the other wire from the thermosensor goes to ground. So I hooked up an ohmmeter to the blue wire and let the engine heat up to the point of almost overheating, yet the reading never varied from 580 ohms with ground as reference. This is a new thermosensor. The old one would start at 2500 ohms when cold and drop to 250 ohms when in boiling water, measured from one lead to the other. I calculated that 250 ohms failed to pass enough current to trip the relay (which I found would only trip with something like 50 mA of current). So I disconnected the connector at the thermosensor and installed my own wires, with one wire going to ground and the other going to the terminal on the radiator fan relay where the blue wire would normally go. I also cut the yellow wire going to the relay. It came from the radiator fan timer, and I jumpered from the white/yellow wire (fused power) to the terminal where the yellow wire previously went. I wanted to make sure that there was unobstructed power supply to the thermosensor via the radiator fan relay (because I wasn't trusting the radiator fan timer at this point). With these two changes, the fan now comes on when the temperature needle gets to the half way point, and the fan stays on for a while after I turn the car off. This operation seems to be O.K., though I am a bit concerned about the lack of a current limiting through the thermosensor arm of the circuit (even though this should be a self-limiting circuit because the thermosensor resistance keeps dropping until enough current passes to trip the radiator fan relay, which in turn cools off the system and thereby reduces the resistance and current at the thermosensor, which will soon turns off the radiator fan relay ... it's a feedback system). Other people have run the fan by putting it in series with the thermosensor, something I would never do. And still others have wired their fans to run full time, also a poor choice IMO. Anyway, if your fan isn't coming on, I suggest that you check the resistance to ground at the blue wire of the radiator fan relay and make sure that it drops as the engine heats up. If it doesn't, you can try my fix. Also check to make sure that your thermosensor resistance drops enough when it gets hot.


Modified by arluk3 at 12:52 PM 11/7/2007


Modified by arluk3 at 8:29 AM 11/8/2007

89efDUSTY

iTrader: (4)

you would get better responses for this if you had it moved to the classic forum. have a nice weekend!