ok I'm repairing my friends 90 cavalier 4cyl auto.
the fan will not come on. so it's overheating.
the a/c clutch will not engage when she turned it on. so no A/c.
these are why she brought it to me. now the engine wiring was a jerry rigged disaster so i replaced it all with a better harness that i checked out before i installed everything in the harness is fine and now installed. it's easier to work with decent wiring so your not fighting 2 problems.
there is also a brand new coolant temp sensor.
and jumping the relay will turn on the fan
and still the fan will not come on if i leave the car running in the garage, and the a/c isn't working. whats going on with this car????????
You've jumped the fan relay and the fan came on. Good. You know the fan motor is good. On the '90 there should be a separate cooling fan switch on the motor similar to the coolant temp sensor. You need to find it. It will have only one wire to the connector. (The coolant temp sensor has two or three wires.) Find the fan switch and disconnect the connector. Ground the wire to the block with the ignition on.
If the fan doesn't come on, change the fan relay.
If the fan comes on, change the cooling fan switch.
Now for the AC. First, check the fuses. It may sound stupid but I'm a master tech and have made dumber mistakes than that. Take the connector off the AC compressor clutch. Probe the red or yellow wire with a test light. Turn on the AC. If the test light comes on, the clutch is bad. Replace it.
If the test light doesn't come on, plug the connector back into the clutch. On the receiver (the silver or black cylinder with metal pipes connected to it on the firewall), find and unplug the low pressure switch. Jump the two wires in the connector with a wire or paper clip. Now turn on the AC. If the compressor clutch kicks in, you need to check the system for leaks and recharge it. If the clutch doesn't kick in, check the defroster switch on the dash. You'll need the shop manual to determine where the AC system gets it's power from. I'm winging this as my ShopKey machine is down right now.
