Elect fan woes

Looking for the location of the electric fan relay and which one it is, and if anyone has the ohm figures on the temp sensor for it. Rig is an 88 with the 4.0, AT and A/C. I take it the sensor is the one in the drivers side rad tank.... BTW fan is good, put 12v on it and works good.

Driving around on the flat it is good, but start pulling a grade and when you shut her down, starts boiling in the overflow. Has new w/p, hoses,and all alum wide core 2 row rad, and thermostat that is opening.

Fan relay is on the driverside inner fender.............sensor is a switch and either has continueity or not.

I hooked a switch in the dash (two wires) from the thermal switch in the lower left side of the radiator. Anytime my temp starts to creep up, I turn it on myself. The thermal switch in the lower left of the radiator turns the fan on often, a little past too late. My thermal switch closes and turns the fan on at 209 F, I've heard others say there there switch closes at an even higher temperature.

What you describe sounds like you have air trapped in the system, search burping the system. A pinhole leak or seep someplace can cause the same thing to happen. When the motor goes into cool down, it can suck a little air in a seep hole or small leak which eventually builds up to an air blockage, which messes with the coolant flow.

Does your fan come on when you turn the A/C on? If it does it's likely air, if it doesn't there may be something wrong with the wiring, fuses or the relay. Possibly the thermal switch.

A/C needs to be looked at. Have not used it since it is not blowing cold, either a leak or needs charged, and will be converted to 134.

8Mud-thanks for the diagram, that be a big help.