Radiator fan not working

[18Fiatsandcounting]

To add to what toyfiats mentioned above, one very common issue (and extremely simple to fix) is that there is not enough coolant in the expansion tank (often called overflow tank). The way that the system is supposed to work is that the engine warms up, warm coolant slowly expands into the expansion tank, and then upon engine cool-down, this coolant is pulled back into the radiator. If you don't have enough coolant in the expansion tank, air gets sucked back into the radiator which causes air pockets and then overheating.

Solution: Make sure that the coolant level in the expansion tank is above the thin tube in the center. And check your radiator cap because it must work in both directions: let coolant out of the radiator when it heats up, and let coolant back into the radiator when the engine cools back down.

-Bryan

[spider2081]

Does the meter you have measure ohms? If it does turn the function to the largest ohms scale and turn on the meter. With the leads ends not touching each other see what the meter displays. this is what your meter displays for an open switch or contacts. Now select the lowest ohms scale and hold the meter probes together. This is what the meter displays for a short circuit or closed switch. leave the meter switch in this position and connect one meter leads to each of the pins on the fans switch connector. The switch in the bottom of the radiator.when the engine is cold the meter should display an open. After the engine warms up to something around 190 degrees the switch should close and your meter should display what it did for a short ( when the meter leads were held together).

[ThatDudeRalph]

Hey guys, Jumping in to ask if the temp sensor on the radiator that controls the fan is ever suspect? I have the same problem as OP but the previous owner just ran a switch to the cabin that powers the fan, I just flip it when the car gets to 190. I figured the issue was the temp sensor and ordered a new one and have yet to install it. But since no one has brought it up it makes me think the sensors aren't known to go. Are air issues far more likely?

[18Fiatsandcounting]

Jumping in to ask if the temp sensor on the radiator that controls the fan is ever suspect?

These do go bad, even brand news ones out of the box occasionally have issues. Although air in the system is the more likely issue, bad fan switches and stuck thermostats do happen.

A simple test is to put a pan of water on the stove, connect an ohmmeter to the switch leads, and heat up the water and see if the switch closes. That should happen around 92 to 95 oC, which is 200 to 205 oF or so. You can also do this with the thermostat and verify that it opens.

-Bryan

[Rweiss6]

Thanks to this forum’s members, fan is working !!
I have added coolant, it was just above spike , and minimum mark on bottle , but maybe was still too low.
I sandpapered contacts again, the ground on upper connection was def gummy and dirty,
Fan first started working at approx 235 degrees, making me nervous , but I waited - thanks to instructions received here.
I have let it cycle bunch of times, temp the fan starts at has steadily dropped. It just went on as needle was just barely touching the 0 of 190. Great progress.
I think I had dirty contacts , low coolant and air in system. I’ll let fan cycle some more now, will let engine cool down again, at least once more and that may do it.

Wonder - does fan need any lubrication?

This post and archives so very helpful. Thanks again to all.

[dinghyguy]

Just one other comment: The black sensor on the top of the head sometimes fails and screws up the temp sent to the gauge from the red sensor (at front of head by spark 1) Unplug the black wire test the car, get it warm, watch the fan come on and off, then connect the black sensor and confirm the gauge does not change. If the gauge jumps up replace the black sensor.

cheers
dinghyguy

[18Fiatsandcounting]

Wonder - does fan need any lubrication?

Not normally, but then again, these fans are 40+ years old. Disconnect the fan motor electrical connector so that something won't happen to do damage to your fingers, and spin the fan blades by hand. Do you feel much resistance? If you let go with your hand, do the blades continue to spin for a bit before stopping? If all feels normal, your fan lubrication is probably fine.

Another test that would require specialized equipment is to measure the current draw on an operating fan motor. These motors are usually 110 watts, which would be about 8 amps at the system running voltage of 13 to 14 volts. If the motor draws much more current than that, it's working hard and that could be due to lack of lubrication.

I have taken apart fan motors and cleaned and lubed them, but these were extreme cases with super crusty old motors. So, it can be done.

-Bryan