Cooling fan not working

[StallonePanerai]

Hey everyone

Today I replaced the radiator and thermostat in my 84 brat. I re-used the original fan switch.  When I put everything back together the cooling fan won’t come on. To be honest I’m not sure if it came on before I put the new radiator in. I just got the car. I did some testing. I unplugged the fan and jumped the wires and the fan came on. Then I unplugged the single yellow connector on the radiator fan switch. I jumped that to ground and the fans came right on. So I thought my radiator might not be grounded enough. I unbolted it and scuffed the paint off the mounting locations. I even took a 1/8” narrow wire brush and cleaned the inside threads of the bolt holes. I also cleaned the little battery ground cable from body to radiator. Than I added a secondary ground strap directly from the radiator to the negative battery cable. Than I removed the fan switch from the radiator and cleaned it up on the wire wheel. I also cleaned the copper gasket. I assembled everything let the car warm up and the cooling fan won’t come on. I am not using and Teflon tape or anything on the fan switch, just the copper gasket. So it should be grounded ok. If I switch the climate selector on the dash to A/C or Defrost the other fan works fine. Since my grounding points are all clean tight and good, and I have power to the fan when jumped can the culprit be the fan switch? That’s the last thing left since everything I mentioned above checked out right? I boiled the fan switch pulled it out of the water and hold it to my ear and when it cools down I hear it click inside. But maybe the clicking doesn’t mean it’s working. I went to Napa for a new switch but won’t be in until Tuesday. Any thoughts????

[GeneralDisorder]

Clicking doesn't mean the contacts in it are any good. Check it for continuity when it clicks. No need to boil it - just heat the end with a torch. If you don't have a meter or test light then rig up a 12v bulb and some wire. 

GD

[StallonePanerai]

The switch has 1 terminal on it. I do have a multimeter. Does the positive go on the plug terminal and the negative on the outside case? Should I check ohms when heating up with a torch? Can someone explain this procedure in depth? I watch a few YouTube videos but still a little confused. 

Thanks

[DaveT]

Terminal is one contact, the body / threads are the other.  Polarity of the meter does not matter, it's a mechanical switch.  It's open or closed.  Only thing to be careful of with a torch is don't get it too much over boiling temp to avoid damaging it.

Connect the ohm meter, it should read open.  Heat the switch, the part that would be in contact with the radiator.  I don;t recall the set point, but when it gets to that temperature, it should read close to 0 ohms on the meter.

Be aware that ohm meters use very small currents, which can occasionally give misleading indications when testing circuits that are designed to carry many amps. 

A more certain test would be to ground the wire that connects to the sensor, and see the fan run.  If it does, then use the fan as the test load- remove the switch, connect it and ground it, then heat it.  see the fan run or not.

[StallonePanerai]

Found the problem today after doing tons of trial and error. All my wires, fuses, fan switch are all good. My brand new radiator even has clean ground contacts with an extra ground wire. The problem is the threaded busing that is soldered to the radiator where the fan switch screws into doesn’t allow enough ground because of the solder for the fan switch to be grounded. I’m even using a copper washer not the rubber o-ring. I’m also not using any sealant or Teflon tape. So it’s a clean mating surface.This is crazy. The radiator I am using is a Spectra. I’m changing to a APDI brand if that has the same issue I guess I will need to buy a OEM from the dealer..... any thoughts or modifications? 

[DaveT]

hmmm....   That doesn't make sense..  Use the voltmeter.  If the threads are clean on the switch and the radiator, that's good connection.  Oring has no effect.  Solder is not going to stop current flow, it's a good conductor.  Connect (-) lead to GND / battery (-).  The other to the thermoswitch body.  Get the switch to trip, or jumper the fan wire to the  switch body to simulate the switch closing.  If the voltmeter reads near zero, the GND side is not the problem.  Also try the (-) lead to the radiator, same tests.

Or simpler - disconnect the wire from the thermoswitch.  Use a test wire to GND it - to the body, the battery (-) the radiator tank.  Try each one.  If the fan runs, the GND at that point is good, and the fan is good.  What works and what doesn't?

 

 

[StallonePanerai]

Please see the attached picture. As you can see the needle is slightly above the line. Right where the needle is in this picture is when the cooling fans come on. And they will shut off when the needle is on the line right below. Is this normal? I thought the fans should come on a little earlier.... this is with the new radiator. I thought anything over the 2nd line is running hot?

[DaveT]

These gauges are not calibrated with that sort of accuracy.   I have had several similar cars, all same GLs and Loyales.   Some read around 1/4, some read around 1/3 of where the red mark starts.  I just learned what was normal for each car.  If it ever goes much above that car's normal, something was wrong.  The temp the fan runs at is controlled only by the thermoswitch, which has a defined range of operation. 

[StallonePanerai]

Im Sure That’s my normal range than. The fan switch will do its job. Thank you!