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autodoc_2000, Auto Technician
Category: Chevy
Satisfied Customers: 2563
Experience:  ASE Master Tech W/Advanced Engine Performance
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2001 Cavalier: 2.2 w/5 speed--Cooling fan on radiator..12V..jumper

Customer Question

2001 Cavalier, 2.2 w/5 speed--Cooling fan on radiator will not come on. Fan motor is new and will run when 12V is supplied directly to motor with a jumper. Changed relay under hood (in black plastic box) with a known good one from another running Cavalier. (Fan worked on the other Cavalier) Checked the 30Amp fusable link with a meter for the blower motor, it was good.

Am assuming the temp sensor is ok, as it registers normal when going down the road and indicates overheating when the car idles for an extended period of time. (3 to 4 minutes) When it does overheat, antifreeze comes out of the overflow and lands directly on the serpantine belt, throwing it off the pulleys and idlers. What would you suggest next?
Submitted: 8 years ago.
Category: Chevy
Expert:  autodoc_2000 replied 8 years ago.

Here is the wiring diagram. Check for power to the relay at the pins listed. If you have power try jumping across 87 and 30 to see if the fan runs. If it does check for power on pin 85. If you have power there then the computer is not grounding. So it could be the sensor or the computer.



Customer: replied 8 years ago.

Jumping across 87 and 30, the fan runs

checking with one probe to battery gtound and the other to 85, I get 12 volts


Would you suggest trying a new temperature sensor even though the dash temperature gauge appears to be working correctly? Am I correct in assuming that the temp sensor on the left hand side front of the motor controls both the temp ga. and the cooling fan?

Expert:  autodoc_2000 replied 8 years ago.

Do you have a/c? If so try turning the a/c on to see if the fan comes on. It does appear that they do share a sensor. Here is the location.




Customer: replied 8 years ago.

Fan does NOT come on when A/C is turned on.


I am assuming the sensor is working, as the temperature ga on the dash works as it should and will show a overheating condition if allowed to idle for a period with no air flow across the radiator. I also tried jumping across the two wires when removed from the sensor with no motor movement. The car runs just fine as long as it is moving and has air flow across the radiator.

Expert:  autodoc_2000 replied 8 years ago.
The next step is going to the PCM and doing an ohm reading through the wire to the relay control. Use the wiring diagram above, pin 54 connector 2. Unplug the PCM and the relay. Let me know what reading you have.
Customer: replied 8 years ago.

I must leave for a couple of hours. I will need to get back to you later. I did not think it would take this much time. Please let me know how to contact you by email for a follow up to cure this problem. Because I value your time, I am going to hit the accept button. It will take me some time to remove the PCM. My son has the identical car with the only difference being the color. Can any harm be done by switching PCMs. Where is the computer located on the Cavalier, and again can any harm be done by switching them from car to car? Any precautions need to be taken?


My e-mail is [email protected]


Also, noted that there is always power to 30 and 85 on the relay socket and the fan will run if 30 and 87 are jumped.


For a temp solution, can I wire the fan to run continuiously until I find my problem? If so, where would you suggest I take the power from so it will only run when the key is on? I live in the Milwaukee area, so I need the fan operating when in city traffic.

Expert:  autodoc_2000 replied 8 years ago.

Just come back to the site and log in. It should take you to your question. As long as the part numbers are the same you can switch them. You can hook it up to run continually, but I am not sure where to have you hook it up to. You could run a fused switch from the two connectors under the hood and flip it on and off manually.



Customer: replied 8 years ago.

Thanks, XXXXX XXXXX home a little while ago. I may try to put a manual switch along with an indicator light on tomorrow. I am going to keep this thread open for a while longer, but I will hit the accept button for you. This is the first time I have used this service and was not aware that I could get back in touch with you. I have thought that I may have a bad connection or a wire that is open someplace, but how do you find it the way they build cars now. I am quite familiar with the way an automobile is assembled today, as I was a supervisor for American Motors here in Milwaukee.


I bought this car new so I know its history. The wireing diagram you sent came through kind of fuzzy and I can't make out the numbers, but I may try to enlarge it and hopefully I can see the numbers and the letters.


Thanks for your help.

Expert:  autodoc_2000 replied 8 years ago.
The easiest way to fix a broekn wire if there is nothing else on the circuit is to overlay a new wire and splice it at both ends to a piece of wire attached to the terminal in the connectors. Without doing it this way you get into alot of time just trying to access the harness.
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Customer: replied 8 years ago.

I ended up running a hot wire with a fuse and switch to the fan until such time as I can devote to tracking down the wires. I took it into town today, flipped the switch when I was in heavy traffic and the temp gauge never went past the halfway mark. The only thing I can think of is a bad connection or a break in a wire someplace, but the way they make the wireing harnes for the cars now days, it is near impossible to locate it. If you should come up with any other suggestions, email me. I still need to locate a hot wire that goes off with the ignition switch.


Thanks for your help. I will hit the accept button.