cooling fans only work if a/c on ?????

[1995oldsaurora]

hello everyone,,,has anyone experienced this same problem or have any ideas..i have a 95' aurora,the cooling fans will only work if the a/c is on..as soon as the a/c is turned off the fans turn off,regardless of the temperature..any ideas

[Autobanaurora]

The dealer told me on my 98 the fans don't come on until 260 degrees AC or no AC. I find this to be a little hot. I think I'll drop the 180 thermo in and see if that helps.

[1995oldsaurora]

Originally Posted by Autobanaurora

The dealer told me on my 98 the fans don't come on until 260 degrees AC or no AC. I find this to be a little hot. I think I'll drop the 180 thermo in and see if that helps.

if the dealer told you that he's wrong..the low speed fans should turn on at 223 degrees and off at 216 degrees...the high speed fans turn on at 230 degrees and off at 221 degrees..this i know for fact...mine are not doing either ??

[Retro-D]

Originally Posted by 1995oldsaurora

if the dealer told you that he's wrong..the low speed fans should turn on at 223 degrees and off at 216 degrees...the high speed fans turn on at 230 degrees and off at 221 degrees..this i know for fact...mine are not doing either ??

If you have the service manual you will see the circuit consists of three underhood relays. They used a system of series parallel connections for the fan motors to give low and high speeds. At 223 both fans are connected in series (low speed), at 230 they switch to parallel (high speed). First check to see if both fans are coming on when the air is on, not just one.

[Autobanaurora]

Thanks for the info, didn't think the dealer knew what he's talking about. Seems like I have heard the fans in the 98 run. Good thing they have forums like this or those idiots could tell you anything.

[1995oldsaurora]

Originally Posted by Retro-D

If you have the service manual you will see the circuit consists of three underhood relays. They used a system of series parallel connections for the fan motors to give low and high speeds. At 223 both fans are connected in series (low speed), at 230 they switch to parallel (high speed). First check to see if both fans are coming on when the air is on, not just one.

thanks for the reply,,yes both fans turn on when a/c is on..

[Retro-D]

Originally Posted by 1995oldsaurora

thanks for the reply,,yes both fans turn on when a/c is on..

Both fans operate, that means your fuses and fans are good! The coolant sensor is wired to the PCM, the PCM then activates the fan relays according to the measurement from the coolant sensor. You may have a faulty fan relay (there are three) or PCM, if you wish to dig deeper into the wiring let me know and I can attempt to walk you through some further troubleshooting.

[1995oldsaurora]

Originally Posted by Retro-D

Both fans operate, that means your fuses and fans are good! The coolant sensor is wired to the PCM, the PCM then activates the fan relays according to the measurement from the coolant sensor. You may have a faulty fan relay (there are three) or PCM, if you wish to dig deeper into the wiring let me know and I can attempt to walk you through some further troubleshooting.

are the relays along the firewall..or under that black plastic box on the right side of the engine ??

[Retro-D]

Originally Posted by 1995oldsaurora

are the relays along the firewall..or under that black plastic box on the right side of the engine ??

Two of the three relays are on the passenger side in a 'relay center' (across from steering pump). The third is on the passenger side firewall. There are three relays in a row that look the same back there, the fan relay is the one outter most towards the passenger side.

[1995oldsaurora]

Originally Posted by Retro-D

Two of the three relays are on the passenger side in a 'relay center' (across from steering pump). The third is on the passenger side firewall. There are three relays in a row that look the same back there, the fan relay is the one outter most towards the passenger side.

i decided to have the problem scanned at a local garage,rather then guess what was wrong..after $150.00 dollars later and 3 new relays,fans still are not kicking on..i did locate the engine coolant sensor,but looks very difficult to replace..what next

[Retro-D]

Originally Posted by 1995oldsaurora

i decided to have the problem scanned at a local garage,rather then guess what was wrong..after $150.00 dollars later and 3 new relays,fans still are not kicking on..i did locate the engine coolant sensor,but looks very difficult to replace..what next

A garage with a Tech 1 scanner would have enabled the fans and been able to replace just the defective relay or wire. The coolant sensor is used by the PCM and also for the gage cluster data. The tech 1 scanner can also read the engine temp directly for sensor testing. A crude test is if your temp gage is reading normal then the sensor is maybe ok. The PCM sends out two signals (grounds) to operate the fans. Both signals must be present to operate both fans at high speed, which you have confirmed as working (a/c on).

Now for a no cost test. If you are able to do this yourself remove the connector from the bottom of fan relay #1 (on the firewall). There may still be a green plastic clip, if there is remove it so the tab can be depressed to unplug the relay. Once that's done you will see the four connections on the socket (not the relay). You can force the fans to operate at low speed for a brief test. Use a short piece of wire to jumper the large red and black leads on the socket, both fans will come on if the fans, wiring and relay #2 are good.

[1995oldsaurora]

Originally Posted by Retro-D

A garage with a Tech 1 scanner would have enabled the fans and been able to replace just the defective relay or wire. The coolant sensor is used by the PCM and also for the gage cluster data. The tech 1 scanner can also read the engine temp directly for sensor testing. A crude test is if your temp gage is reading normal then the sensor is maybe ok. The PCM sends out two signals (grounds) to operate the fans. Both signals must be present to operate both fans at high speed, which you have confirmed as working (a/c on).

Now for a no cost test. If you are able to do this yourself remove the connector from the bottom of fan relay #1 (on the firewall). There may still be a green plastic clip, if there is remove it so the tab can be depressed to unplug the relay. Once that's done you will see the four connections on the socket (not the relay). You can force the fans to operate at low speed for a brief test. Use a short piece of wire to jumper the large red and black leads on the socket, both fans will come on if the fans, wiring and relay #2 are good.

well i have some good news...i was checking the 3 fan relays again and found that the low speed fan relay was not fully seated in the socket..fans are kicking on as they should now...thanks for all the help..

[Retro-D]

Originally Posted by 1995oldsaurora

well i have some good news...i was checking the 3 fan relays again and found that the low speed fan relay was not fully seated in the socket..fans are kicking on as they should now...thanks for all the help..

That's great to hear! Maybe this thread will help someone else with the same trouble in the future.