this has crept up withing the past 2 days. the radiator fans have begun constantly running while the car is running. they stop when I cut the car off though. bad coolant temperature switch? or partially stuck thermostat?

 

Low coolant possible cause. Stuck Fan Relay possible. What happens when you turn on A/C. Possible coolant temp sensor. A/C on both fans should come on when compressor cycles. Only one fan should operate with A/C off and coolant reaches proper operation temp.

 

OHD - I think that both fans will turn on when the coolant reaches the max temperature on the sensor.

Drummer - When you first start the engine and the fans are running, unplug temperature senor A. That way you know for sure that the coolant temperature is not too hot. Sensor A is on the thermostat housing. If the fans stop running, then you pretty much verified the sensor as the problem.

 

that is correct. regardless if I run the A/C or not, both of the fans engage when they are signaled to. my coolant level is perfect, and I am not running hot, I just had the timing belt set replaced in January. I did just put 1200 miles on it in a span of a week, but I travel a lot for work so it's not uncommon.

 

Unplug the fan-switch-A to verify that the fans DON'T run when it's unplugged. If they don't run, then it's a bad fan switch. If they still run, then those 2 wires in that plug are shorted against each other somewhere(!).

 

this is intermittant. they didn't constantly run the past 2 days. then tonight on the way home from work, they started again. when I got home, I let them run until the Tem. guage was well below where the fans would not run. I can not find a sensor on the actual thermostat housing in the back, but there is one on the loo alike housing in the front that the top radiator hose goes into. I unplugged that, and they still ran.

 

Temp sensor A is #14 in the picture.

 

aaahh I found it, It was covered in gunk and buried under distributor cap and ignitor wires.

 

Ok I'm reading this maybe a bit different.

So sometimes the fans cycle on and off as normal. But sometimes they come on and stay on - no cycling - until you turn off the car. You could have a sticking relay, more tests needed before replacing.

PA has given you the location of the switch (green color). Please do the test EDIT: JIM has suggested and let us know what you find.

 

Next time you catch it running continuously, leave the engine running & open the hood. Unplug that switch.

If the fans keep running when the switch is unplugged, then it's likely a stuck relay.