jjjr944

Radiator fans worked last summer in all modes--Low, high and the
run-on mode which allows fan to continue to cool after engine is turned off and key is removed. Fans stop after prescribed cooldown temp is reached.

I did an AC charge this spring, and although I think this is unrelated, the run-on portion of the fan no longer funtions. When hot the fan will stay going with engine on or key in no. 2 position, but not when key is turned off. Both fans work, one when AC is NOT on and both with AC on.
Anyone come across this problem and a solution?

Gotta thank xsboost and nine-44 last nite for the tour of the black beast . It's coming along & looks great. Our consensus last nite was thermo temp switch or fan relay.
Any thoughts or similar experiences with possible remedies would be appreciated.
Thanks!

Jerry
jjjr944
1986 944 NA
65,000mi
Guards red/Black leather
Certified non-modified virgin (the car.....not me)

TheMAXX

I have an 84 and I don’t know exactly what they changed on the newer cars. On an 84 the keep running mode is activated by the thermal switch in the radiator and a resistor that is wired across the relay closure. So the relay is not in use at all for this mode of operation. I think on all of the newer versions the Thermal switch has 3 contacts instead of just 2. But I am not sure what the difference is in operation. I just looked at the wiring diagram in the Haynes manual and it looks like it works the same way as the 84 with the resistor across the relay. If the fans run with the ignition switch on when the engine is hot (as you say in your post) but the engine is or isn't running. Then it is ether that additional terminal (3 contacts) on the thermal switch or the resistor. Are you sure that you didn’t bump the wires to the thermal switch when doing the A/C work. You should be able to remove the connector at the thermal switch and jumper the contacts (you can do this with the engine cold so you don’t burn yourself) and with the ignition off and the proper contacts shorted the fan should run if everything but the thermal switch is working. If the fan still doesn’t run I would suspect the resistor. I thought I remember someone saying it is up behind something in the dash.

Air in the system can also do some funky things. The thermal switch is in a location that if there is air in the system the switch can sit in an air pocket and not get good enough coupling with the coolant to work properly in my opinion.

I hope this may be of some help.