Rad Fans not coming on for 2001 Trans Am
08-27-2016, 11:15 PM
#1
Rad Fans not coming on for 2001 Trans Am Fans don't come on at all.
Autometer gauge reads 250 F.
Scan Tool reads 245 F.
Dash gauge reads 225 F.
Even with the A/C on the fans don't come on.
30 amp Fuses are fine.
Swapped relays.
Ran 12 V straight to the fans...they work.
What am I missing?
Autometer gauge reads 250 F.
Scan Tool reads 245 F.
Dash gauge reads 225 F.
Even with the A/C on the fans don't come on.
30 amp Fuses are fine.
Swapped relays.
Ran 12 V straight to the fans...they work.
What am I missing?
08-28-2016, 09:12 PM
#2
Looks like there's 2 fuses, and 3 relays for both fans. I'd say you have a power, ground or PCM issue.
One 40amp fuse and one 10amp fuse. Both are "hot at all times". I'd start there and make sure you have power at fuses and to the relays.
Kyle
One 40amp fuse and one 10amp fuse. Both are "hot at all times". I'd start there and make sure you have power at fuses and to the relays.
Kyle
08-29-2016, 05:35 AM
#3
^Good place to start. Look for common circuits shared by both fans since both should be running at 245* F. If power checks out as above, the fans likely have a bad ground.
Since there 2 separate control wires from the PCM to the relays and neither fan is working, the probability that both of those crapped out at the same time is minimal.
Since there 2 separate control wires from the PCM to the relays and neither fan is working, the probability that both of those crapped out at the same time is minimal.
08-29-2016, 11:34 AM
#5
i don't have it at the moment but if you search on here you can find the radiator fan PCM wiring diagram. there are 2 "low current" ground wires from 2 of the 3 radiator fan relays that go to the pcm... a green and a blue wire. if you ground one (forget which color) then fans come on low speed, ground both and both fans come on high speed.
the pcm has a "forget what it's called" circuit that switches either of those wires to ground to activate the relays... then the relays act like on/off switches to turn the fans on/off {the relays are the high current switch, the pcm cannot be the high current switch}. And other things like headlights, horn, fuel pump {whatever needs significant power} works this way.
for your fans, access the green and blue wire that goes to the pcm. the "radiator fan mod" is all about this for manual control of the fans, what u can do to narrow things down is just before the PCM take those green & blue wires and hook them to ground, fans should come on. If they do then it's likely the circuit in the PCM burned out and can no longer control the radiator fans. If fans don't come on, then that's a good thing cause it's likely not the pcm, and the problem is somewhere in the wiring.
the easiest/cheapest way to tap into the green & blue wire is using a scotch-lok.
the pcm has a "forget what it's called" circuit that switches either of those wires to ground to activate the relays... then the relays act like on/off switches to turn the fans on/off {the relays are the high current switch, the pcm cannot be the high current switch}. And other things like headlights, horn, fuel pump {whatever needs significant power} works this way.
for your fans, access the green and blue wire that goes to the pcm. the "radiator fan mod" is all about this for manual control of the fans, what u can do to narrow things down is just before the PCM take those green & blue wires and hook them to ground, fans should come on. If they do then it's likely the circuit in the PCM burned out and can no longer control the radiator fans. If fans don't come on, then that's a good thing cause it's likely not the pcm, and the problem is somewhere in the wiring.
the easiest/cheapest way to tap into the green & blue wire is using a scotch-lok.
08-29-2016, 11:44 AM
#6
ground the dark green wire only, and both fans come on low speed.
this is pin 42 going to pcm
ground both green and blue wire (pin 33) gives both fans on high speed.
if you ground just the blue wire pin 33 then i believe only the right fan comes on high speed left fan stays off- this is normal because of the way the 3 relays work.
note the 3 relays, 2 of them are identical but the middle one is a double pole. so you need to make sure the correct relays are the correct position in the underhood fuse box.
this is pin 42 going to pcm
ground both green and blue wire (pin 33) gives both fans on high speed.
if you ground just the blue wire pin 33 then i believe only the right fan comes on high speed left fan stays off- this is normal because of the way the 3 relays work.
note the 3 relays, 2 of them are identical but the middle one is a double pole. so you need to make sure the correct relays are the correct position in the underhood fuse box.
08-29-2016, 12:50 PM
#7
i don't have it at the moment but if you search on here you can find the radiator fan PCM wiring diagram. there are 2 "low current" ground wires from 2 of the 3 radiator fan relays that go to the pcm... a green and a blue wire. if you ground one (forget which color) then fans come on low speed, ground both and both fans come on high speed.
the pcm has a "forget what it's called" circuit that switches either of those wires to ground to activate the relays... then the relays act like on/off switches to turn the fans on/off {the relays are the high current switch, the pcm cannot be the high current switch}. And other things like headlights, horn, fuel pump {whatever needs significant power} works this way.
for your fans, access the green and blue wire that goes to the pcm. the "radiator fan mod" is all about this for manual control of the fans, what u can do to narrow things down is just before the PCM take those green & blue wires and hook them to ground, fans should come on. If they do then it's likely the circuit in the PCM burned out and can no longer control the radiator fans. If fans don't come on, then that's a good thing cause it's likely not the pcm, and the problem is somewhere in the wiring.
the easiest/cheapest way to tap into the green & blue wire is using a scotch-lok.
the pcm has a "forget what it's called" circuit that switches either of those wires to ground to activate the relays... then the relays act like on/off switches to turn the fans on/off {the relays are the high current switch, the pcm cannot be the high current switch}. And other things like headlights, horn, fuel pump {whatever needs significant power} works this way.
for your fans, access the green and blue wire that goes to the pcm. the "radiator fan mod" is all about this for manual control of the fans, what u can do to narrow things down is just before the PCM take those green & blue wires and hook them to ground, fans should come on. If they do then it's likely the circuit in the PCM burned out and can no longer control the radiator fans. If fans don't come on, then that's a good thing cause it's likely not the pcm, and the problem is somewhere in the wiring.
the easiest/cheapest way to tap into the green & blue wire is using a scotch-lok.
ground the dark green wire only, and both fans come on low speed.
this is pin 42 going to pcm
ground both green and blue wire (pin 33) gives both fans on high speed.
if you ground just the blue wire pin 33 then i believe only the right fan comes on high speed left fan stays off- this is normal because of the way the 3 relays work.
note the 3 relays, 2 of them are identical but the middle one is a double pole. so you need to make sure the correct relays are the correct position in the underhood fuse box.
this is pin 42 going to pcm
ground both green and blue wire (pin 33) gives both fans on high speed.
if you ground just the blue wire pin 33 then i believe only the right fan comes on high speed left fan stays off- this is normal because of the way the 3 relays work.
note the 3 relays, 2 of them are identical but the middle one is a double pole. so you need to make sure the correct relays are the correct position in the underhood fuse box.
I put in a switch temporarily to turn on the fan by connecting a ground lol.
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08-29-2016, 03:41 PM
#8
I have a similar issue, and I think it's pcm related. In HPtuners, I can command on the fan, and it'll run for 3-4 seconds, then it shuts off. Sounds like a relay problem right, nope, if I connect a ground to the pcm wire the fan runs. So for some reason, the pcm only sends the signal to the fan for 3-4 seconds then stops.
08-30-2016, 09:21 AM
#9
So if the car is on, my jump switch doesn't work. I have to turn it on when the car is off and it will stay running when the car is on. But not if I try to start it with the car on.
Gonna try to jump off the dark blue wire on the 10 pin harness by the PCM instead.
Gonna buy 3 new relays instead of swapping them around.
Gonna try to jump off the dark blue wire on the 10 pin harness by the PCM instead.
Gonna buy 3 new relays instead of swapping them around.
08-30-2016, 06:46 PM
#10
Swapped all the relays out for new ones. Fans ONLY come on if you turn the A/C on. Otherwise it'll let the car go into the red.
I was going to attempt this mod but I have 4 connectors not 3?
http://www.xious.com/camaro/install-fanswitch.html
I was going to attempt this mod but I have 4 connectors not 3?
http://www.xious.com/camaro/install-fanswitch.html
01-24-2019, 03:54 PM
#12
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If your fluid is low! Had the same issue. If your fluid is low the sensor does not pick it up and will not work correctly. Use the little valves to make sure all the air is out of the system and add fluid as required. Once the fluid is high enough it will start to read again and the fans will work. Happens every time I do any work to the cooling system.