cooling fan wont go on
Country: United StatesMake: PontiacModel: sunfireYear: 1997Engine: 2.4
replaced temp sensor-no effect. by passed relay and it would work only while keeping it "jumped". Replaced relay-no effect. Even when turning on the air conditioner the cooling fan would not engage
Hello I will help you with your question,
Have you scanned this to see if there are any engine codes?
Do you have a voltmeter to see if the PCM is trying to turn the fan on?
Let me know so I can help you
yes. there was a light on and the code was something like " cooling system fault" not sure of the wording here. but the engine light is on still but I do not recall the code. but the guy said that something was not telling the fan to go on.
OK, the reason for the code will have to be addressed. There is a driver in the computer that grounds the relay to turn on the cooling fan so you have tested the fan and relay with the power supply for the fan and all of that works so next is to see why the PCM is not turning on the relay.
Normally the fan will be on when there is any sort of cooling system fault so it is likely that the PCM will have to be replaced.
The only test is to command the PCM to turn the fan on with a good scantool (Tech2 or Snapon or OTC) and see if the PCM is trying to ground the relay by measuring directly at the PCM connector with a voltmeter referenced to voltage.
If the PCM does not ground the relay you will need to replace the PCM. If it does ground the relay you have a fault in the wiring between the PCM and the relay
Let me know what I can do to help you with this
It sounds like you are thinking that the PCM is the most likely problem ? that would make sense to me. I dont have a scanner so, I can pick up a PCM for $50 and put it in, Right, simple swap out as long as the PN match?
Yes, you can do this but it would be best to find out the code so I can double check that it is not something that will destroy another PCM when you plug it in.
These PCMs don't have much protection built in and if there is a dead short to voltage on the wire the PCM is trying to ground the driver in the PCM will burn out like a fuse and even though it is trying to turn on the component (relay) it will not be able to.
Let me know if you can find out what code is now set. P0117 or P0118? maybe?
I will do this and tell yo u the code
Great, it is best to be sure before putting a PCM in.
Please let me know so I can help
P0480 is the code...what to do with that ??
That is a generic code to tell you the cooling fan is not working. Try removing the coolant sensor connector and installing a paperclip between the pins of the connector. Insulate it from touching any metal and turn the key on for 1 minute then see if the fan is on. If it is not pull the relay and install a testlight or voltmeter between pins 85 and 86 of the relay socket. The numbers are marked on the relay.
Let me know if the voltmeter shows battery voltage or the testlight is on.
If it is not on see if you have voltage to either 85 or 86 to a clean metal part of the engine.
Let me know what you find so I can help
thanks for waiting for me. okay when i put in the paper clip the fan did not go on. I left it in there with the key on for 2 minutes...nothing. Also there is power at pin 85. No power at 86. When taking a test light from 85 to 86 there is not any power-the light does not go on.
Ok, we will have to work on getting power to the relay then.You say you jumped the relay? This was at the 87 and 30 pin sockets?if so the relay is fed from a single fuse so if the fan came on by jumpering the pin sockets then the problem is in the relay sockets.I am on the road right now and will be at a real computer in about 1 1/2 hours so i can see your reply at that time.Let me know how you got the fan to run and which pin sockets you have power to so I can helpSorry for the delayThank you
Yes, I jumped the relay from pin 87 to 30 and the fan opperates fine.
Ok you are going to have to see the red wire that feeds pin 87 or 30 and see if you can find the break. The red wire should feed pin 85 or 86 as well with a Dark green to the other pin. Both red wires to the relay are fed from the same fuse so if one is hot the other should be as well. I don't know if the break is at the relay or the fuse but it is between those two points. You can splice a jumper from the red wire feeding 87 or 30 to 85 or 86 (whichever is NOT attached to the green wire) and th relay will operate and the fan will run.Let me know what you find, as I say I am on the road and I will look for your reply as soon as I canThanks
okay...the red wires always have power... pin 86 and 87 dont seem to ever have power ..I hot wired pin 86 and the fan stays on the whole time with the relay installed. thats all I have to tell you..I am confused as to what is the problem with the wiring. where does 86 and 87 's wires go to ???
If you provided power to the 86 pin from the 30 pin and the fan stays on then the computer is keeping the fan turned on.
Is this car new to you? Maybe this is why someone cut the power to the 86 pin?
The 85 pin is grounded by the computer when it wants to turn the fan on, the 87 pin is the power to the fan once the relay closes.
A short primer on relay operation,
two pins have battery voltage and one is connected to the load, in this case the fan. The relay acts as a switch so when the pin with power (30) is connected to the load (87) by the internal switch in the relay the fan runs.
Pin 86 is part of a magnetic coil and has power applied, when the computer grounds pin 85 and current flows that causes pin 30 to connect to pin 87 causing the fan to run.
The control and loads can be swapped as it does not matter which way the current flows so pin 86 or 85 could be to the computer and pin 30 or 87 could be to the fan but the other pin in the pair will be to power.
The PCM may still be the problem, a scantool will tell in short order. I have seen many of these wired with a switch to turn the relay on and the driver turns the fan on and off as the gauge shows it is needed.
let me know what I can do to help you with this
okay...just scanned it again. code is p0480. No other codes. soooo I follow partially your Primer but not fully. when I took off the connection from the coolant sensor and inserted a paper clip it failed to turn on the fan: so does this mean that the short is in one of the two wires going to the sensor ??/
The computer will not be able to turn on the relay unless there is power to both the 87 and 86 pins (or 30 and 85) but you need power to two of the pins. If the fan comes on when you supply power to the pin that does not have it but should then shorting the sensor will not turn on the fan.Let me know what you are seeingThank youGeorge H41042.7888174421
by passing 30 or 85 pin to 87 turns on the fan. No by passing to 86 does anything
Ok then the computer is grounding the relay turning it on. It will do this when the code sets so a scantool that can control the PCM is needed to clear the code and command the fan on while the output from the PCM to the relay is measured with a voltmeter to see if the computer is grounding the relay.At this point you can try installing another PCM ( I do think the driver in the PCM is fried) or spend the 1 hours fee for the diagnostic time to have a shop check the output of the computer. I do not think you will destroy a computer installing it, have the relay out when you do, install the computer then the relay and clear any codes in the computer.Let me know what i can do ot help you with thisThank you
okay. I will go pick up a used PCM that I know about from a 97 sunfire. it has the 2.2 engine and mine is the 2.4...should these interchange ? I could possibly find one out of a 2.4 but I have not located one yet. Also, swapping the PCM should or should NOT require reprograming ?? my thought that if it was working in one car then it should work in mine by a simple switch out. Does that sound right to you?
Use the part number on the PCM to match to the replacement that way you can be sure it is the correct one.There should be no programming required.Let me know what happens and how i can helpThank you
thanks for you putting up with my lack of experience. I will go get this done today and get back to you and let you know what s happened.
No problem, I wish I was there with my scantool to put a definitive diagnosis on this but I think another computer will work for you.Please let me know what I can do to help and what happens when you install the computerThanks