96 cooling fan on a switch
Thread Starter
Melting Slicks
Joined: Dec 2004
Posts: 2,656
Likes: 635
From: Dallas TX
96 cooling fan on a switch
Not looking for a long term solution. Just need to get the car to a shop.
reference this thread for my issue:
https://www.corvetteforum.com/forums...t-working.html
I am not good with electrical diagnosis so beyond using a friends Tech 1 computer to activate the cooling fans(can activate them all no problem) and see that no A/C on signal is being received by the ECU, the next 15 steps in the service manual are not my forte. The car has sat for 6 months and I am just going to break down and take it to a shop.
I need to see if its possible to rig up a switch in place of one of the relays so I can turn the cooling fans on manually in order to get the car to the shop(its down in Houston). Im not concerned on the highway, which 95% of the trip would be, but if I got caught in traffic or on any side roads to get to the shop, im concerned with overheating.
I am sure it will trigger a CEL(starting the engine with the 3 relays removed trips a code), im good with that as I understand what its doing.
Im thinking a fused switch I can rig up into the interior of the car to turn the fans on and off as needed. Again, this is just a temporary thing to get the car down to a shop about 200 miles away.
reference this thread for my issue:
https://www.corvetteforum.com/forums...t-working.html
I am not good with electrical diagnosis so beyond using a friends Tech 1 computer to activate the cooling fans(can activate them all no problem) and see that no A/C on signal is being received by the ECU, the next 15 steps in the service manual are not my forte. The car has sat for 6 months and I am just going to break down and take it to a shop.
I need to see if its possible to rig up a switch in place of one of the relays so I can turn the cooling fans on manually in order to get the car to the shop(its down in Houston). Im not concerned on the highway, which 95% of the trip would be, but if I got caught in traffic or on any side roads to get to the shop, im concerned with overheating.
I am sure it will trigger a CEL(starting the engine with the 3 relays removed trips a code), im good with that as I understand what its doing.
Im thinking a fused switch I can rig up into the interior of the car to turn the fans on and off as needed. Again, this is just a temporary thing to get the car down to a shop about 200 miles away.
Last edited by rjacobs; Dec 29, 2019 at 10:18 PM.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
Likes: 207
From: Orlando FL
Yes you can always rig a switch to ground the return of the fans and make them run.
Why are you going to a shop 200 miles away?
Low Freon the A/C should still come on. Even a static pressure of 50 -75 it still should start the AC. But I would just jump out the cycling switch and if it does not come on then there is something else wrong.
But aside from that the fans should run in high speed if you get to a temperature of 250. If the fans don't come on, I would forget about the AC and find out why the PCM is not turning the fans on.
Have you tried disconnecting the battery for a minute and then connect. Possibly something might be hung up. Sounds stupid but you never know.
The tech 1 can command the compressor clutch and the fans to be energized. If you can't do that and there are no codes, there could be a PCM problem.
With problems like this, grounds need to be checked.
I have read mostly everything, to much to comment on the initial thread.
Why are you going to a shop 200 miles away?
Low Freon the A/C should still come on. Even a static pressure of 50 -75 it still should start the AC. But I would just jump out the cycling switch and if it does not come on then there is something else wrong.
But aside from that the fans should run in high speed if you get to a temperature of 250. If the fans don't come on, I would forget about the AC and find out why the PCM is not turning the fans on.
Have you tried disconnecting the battery for a minute and then connect. Possibly something might be hung up. Sounds stupid but you never know.
The tech 1 can command the compressor clutch and the fans to be energized. If you can't do that and there are no codes, there could be a PCM problem.
With problems like this, grounds need to be checked.
I have read mostly everything, to much to comment on the initial thread.
Last edited by pcolt94; Dec 29, 2019 at 10:54 PM.
Thread Starter
Melting Slicks
Joined: Dec 2004
Posts: 2,656
Likes: 635
From: Dallas TX
Yes you can always rig a switch to ground the return of the fans and make them run.
Why are you going to a shop 200 miles away?
Low Freon the A/C should still come on. Even a static pressure of 50 -75 it still should start the AC. But I would just jump out the cycling switch and if it does not come on then there is something else wrong.
But aside from that the fans should run in high speed if you get to a temperature of 250. If the fans don't come on, I would forget about the AC and find out why the PCM is not turning the fans on.
Have you tried disconnecting the battery for a minute and then connect. Possibly something might be hung up. Sounds stupid but you never know.
The tech 1 can command the compressor clutch and the fans to be energized. If you can't do that and there are no codes, there could be a PCM problem.
With problems like this, grounds need to be checked.
I have read mostly everything, to much to comment on the initial thread.
Why are you going to a shop 200 miles away?
Low Freon the A/C should still come on. Even a static pressure of 50 -75 it still should start the AC. But I would just jump out the cycling switch and if it does not come on then there is something else wrong.
But aside from that the fans should run in high speed if you get to a temperature of 250. If the fans don't come on, I would forget about the AC and find out why the PCM is not turning the fans on.
Have you tried disconnecting the battery for a minute and then connect. Possibly something might be hung up. Sounds stupid but you never know.
The tech 1 can command the compressor clutch and the fans to be energized. If you can't do that and there are no codes, there could be a PCM problem.
With problems like this, grounds need to be checked.
I have read mostly everything, to much to comment on the initial thread.
As far as the rest of your comments, have you been through the diagnostic steps on the 96 system for cooling fans or A/C? The fans not running check(if it passes, which it did) pushes you to the A/C system and if the "on" command is not received from the PCM(it isnt, the status stays "off" on the Tech 1) then you dive into like 11 or 12 steps on probing lots of sensors. Thats where I quickly get lost since I am not electrically savvy, and none of my buddies down here are either, so I will take it to a shop. I believe its fairly simple and somebody who can do electrical troubleshooting should be able to knock it out fairly quickly.
Le Mans Master
Joined: Aug 1999
Posts: 7,339
Likes: 137
From: WilkesBarre PA
On a 96 both fans run on low then high. Energizing relay 1 they run on low, then 2&3 energize together and they both go on high. Fuse #2 (30amp) & 5(40amp) are power for the fans (always hot), fuse 29 (5amp) is power for the relays (only hot with key on. If you ground the dark green wire on relay #1 the fans should run on low, then grounding the dark blue wire for 2&3 the fans should run on high with all 3 energized. These are the 2 wires the PCM grounds to control the fans.
Are you looking at the digital display for the temp? This is off the cooling sensor on the water pump the pcm also gets it's input from. I forget the actual factory numbers without looking it up, but it's close to 224 for low, then 23x for high. The analog one has no input to the computer and it's sensor is on the pass side head.
Are you looking at the digital display for the temp? This is off the cooling sensor on the water pump the pcm also gets it's input from. I forget the actual factory numbers without looking it up, but it's close to 224 for low, then 23x for high. The analog one has no input to the computer and it's sensor is on the pass side head.
Thread Starter
Melting Slicks
Joined: Dec 2004
Posts: 2,656
Likes: 635
From: Dallas TX
On a 96 both fans run on low then high. Energizing relay 1 they run on low, then 2&3 energize together and they both go on high. Fuse #2 (30amp) & 5(40amp) are power for the fans (always hot), fuse 29 (5amp) is power for the relays (only hot with key on. If you ground the dark green wire on relay #1 the fans should run on low, then grounding the dark blue wire for 2&3 the fans should run on high with all 3 energized. These are the 2 wires the PCM grounds to control the fans.
Are you looking at the digital display for the temp? This is off the cooling sensor on the water pump the pcm also gets it's input from. I forget the actual factory numbers without looking it up, but it's close to 224 for low, then 23x for high. The analog one has no input to the computer and it's sensor is on the pass side head.
Are you looking at the digital display for the temp? This is off the cooling sensor on the water pump the pcm also gets it's input from. I forget the actual factory numbers without looking it up, but it's close to 224 for low, then 23x for high. The analog one has no input to the computer and it's sensor is on the pass side head.
As for the second comment, not sure what it applies to in my situation... Car has been hotter than 250 degrees via the digital readout with no fans(only once when I realized something was not right). I unplugged the sensor on the water pump to eliminate it and the car ran garbage rich which means the sensor is working.
The shop manual steps push me down a rabbit hole of probing sensors and i just get lost at what to do.
