i usually post on the truck forum, but i am a policeman and drive a 99 crown police interceptor. today it overheated and i noticed the cooling fan was not running. i know it is relay protected, but without the manual, i dont know which one to test. can someone please help me out here?
Here's the wiring diagram and the relay locations. The high speed relay is in another smaller box between the main engine fuse box and the heater core. The low relay is in the main box behind the battery. The fan should come on high speed when the air conditioning compressor is running. The low, not until the engine gets over half way. Maxi fuse #13 is for the high speed relay and the circuit breaker #17 is for the low fan relay.
Thanks for doing the work you do. Many people don't realize what you guys have to put up with. I retired from a job installing the equipment and repairing the cars, so I've seen what you guys have to put up with..
thanks so much for the info. having been there, since the fan wont run at all, what would you suggest to try first? i love my job. been at it 22 yrs altogether counting reserve and full time, but sometimes it is testy. to make matters worse, i am chief of the school campus police, and with all the budget cuts in schools today, that leaves us doing the maintenance by ourselves. thanks again!!!!!
If it doesn't run and the A/C is on and cooling. check for power at the orange/light blue wire. If it has power there. the fan motor is bad unless the black wire isn't grounded. We have replaced those fans a few times.
Where are you located? I have a couple of friends that retired from our agency and help at the Monmouth, Or training campus.
If the A/C wasn't kicking in, then that's a different situation. When the pressure switch for the A/C senses pressure, it turns the fan on to high. The engine temp sensor would turn it on to low when the temp goes a little above ½ way up the gauge. Does the A/C work at all?
Have you let it run to see if the fan will come on when the enging gets hot? The PCM controls the clutch but the 2 pressure switches have to be closed. With the A/C on and the engine running, power should gothrough both switches to the PCM. Check the black/yellow wire at the high pressure switch. If no power there, go to the low pressure switch and see if there's power on both sides.
Here's the circuit for the A/C clutch.
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