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Ok so this is my first post on this forum, hopefully someone can point me in the right direction.
My vehicle:
2005 Corvette Z51 (auto trans)
Outside of a Vararam SC1 intake the car is completely stock.
Issue:
So last week I took the car out for a short ride and noticed that the AC wasn't blowing cold. The next day I went to troubleshoot the issue and noticed that the electric cooling fans weren't turning on at all either.
Troubleshooting:
1. Checked the fuses (everything looks good)
2. Jumped power to the fan at the 3-pin connector plug and the fans came on full power. (so I know the fan works)
3. I read on this forum that many people had issues with the plugs, even if they don't look burnt or damaged. So I cut the plugs out and spliced the wires together. (still no luck)
4. I figured it had to be the Fan Control Module ( so I replaced it with a new AC/Delco unit, still no luck )
The only thing I can think to replace next is the ECM/PCM, but I don’t have a scanner to check for codes that might confirm that and money is a little tight at the moment. So I had a couple question and was hoping someone on here could help.
1. Can the ECM/PCM be bad but only be causing the cooling fan not to work?
2. What sort of costs am I looking at for a new ECM/PCM with a simple stock tune?
Of course any other suggestions would be greatly appreciated. Thanks in advance!
Ok so this is my first post on this forum, hopefully someone can point me in the right direction.
My vehicle:
2005 Corvette Z51 (auto trans)
Outside of a Vararam SC1 intake the car is completely stock.
Issue:
So last week I took the car out for a short ride and noticed that the AC wasn't blowing cold. The next day I went to troubleshoot the issue and noticed that the electric cooling fans weren't turning on at all either.
Troubleshooting:
1. Checked the fuses (everything looks good)
2. Jumped power to the fan at the 3-pin connector plug and the fans came on full power. (so I know the fan works)
3. I read on this forum that many people had issues with the plugs, even if they don't look burnt or damaged. So I cut the plugs out and spliced the wires together. (still no luck)
4. I figured it had to be the Fan Control Module ( so I replaced it with a new AC/Delco unit, still no luck )
The only thing I can think to replace next is the ECM/PCM, but I don’t have a scanner to check for codes that might confirm that and money is a little tight at the moment. So I had a couple question and was hoping someone on here could help.
1. Can the ECM/PCM be bad but only be causing the cooling fan not to work?
2. What sort of costs am I looking at for a new ECM/PCM with a simple stock tune?
Of course any other suggestions would be greatly appreciated. Thanks in advance!
Well, you checked for power, (fuse # 25-60A) which is OK, since you got the fan running.
You replaced the control module, so you know that is good.
According to the wiring diagram, the signal to run the cooling fan is sent from the Engine Coolant Temperature Sensor (in front left side of cylinder head) to the ECM (behind right front fender between wheelhouse and dash panel)
The ECM also is responsible to send any alarms (hi coolant temp, etc) to the IPC (inst panel cluster) and HUD
The HVAC control module (center dash under radio) also ties into the computer data line system.
It's possible that you could have a Bad Engine coolant temperature sensor or wiring to or from the ECM. It's worth a check. Also, check the ground wire for good contact from the fan control module (on top of front frame rail)
The Engine coolant sensor has a tan and a yellow wire going to the ECM. If the temperature is above normal, the Dark green wire from the ECM triggers the fan speed through the RED/Orange Wire of the fan control module. The red wire that feeds the fan control module comes from the 60A fuse.
The Tan/Black and Tan from the ECM go to the Data system for alarms.
It's hard to imagine that the ECM is bad. Not likely. Pursue all other troubleshooting venues before even looking at replacing the ECM
I can send you the wiring diagrams (for all c6 systems by e-mail).
PM me your e-mal address and I'll sent it out ASAP.
The cooling fan system is on page 16 in the PDF file
Good Luck
I believe the temperature sensor is functioning properly because the reading on the gauge cluster and on the HUD are slowly rising when the is started and let idle. I let it go up to 200F or 210F before just turning the car off.
In regards to the HVAC, I can turn on the AC and the interior fans blow but it has no effect on the cooling fan itself. The temperature on the center console looks to be accurate as well (not sure if that should display the inside or outside temp though).
I believe the temperature sensor is functioning properly because the reading on the gauge cluster and on the HUD are slowly rising when the is started and let idle. I let it go up to 200F or 210F before just turning the car off.
In regards to the HVAC, I can turn on the AC and the interior fans blow but it has no effect on the cooling fan itself. The temperature on the center console looks to be accurate as well (not sure if that should display the inside or outside temp though).
PM sent for wiring PDF, thanks again!
PDF sent out. I hope it's just a bad wire somewhere, and not the ECM
Could the relay in the engine bay fuse compartment be bad. I am no elect guru at all but i installed the cool it mod where i can bring the high speed in with a key fob art anytime and i had to replace a fuse and a relay when i installed it so i assume the relay i replaed had to do with the fan. Good luck.
In the wiring diagram below ( thanks @LV2TOUR ) I have overlaid some of my troubleshooting.
Blue Sections:
The upper blue section is where I confirmed the fuse looks good.
The lower blue section I am considering to be in good working order because of where I jumped power to it and confirmed the fans worked.
Orange Sections:
These seems to be the only places where I could have an issue based on the diagram.
I know the black/red wires going to the fuse block are wrapped up pretty tight, would you recommend I start at the fan and work my way to the fuse block? Or start at the fuse block and work my way to the fan?
Same question with the speed control wire as well?
Again thanks for all the help!
@bjones7131 -
As far as I know the cooling fans don't have a micro-relay, but I could be wrong?
Well, you checked for power, (fuse # 25-60A) which is OK, since you got the fan running.
You replaced the control module, so you know that is good.
According to the wiring diagram, the signal to run the cooling fan is sent from the Engine Coolant Temperature Sensor (in front left side of cylinder head) to the ECM (behind right front fender between wheelhouse and dash panel)
The ECM also is responsible to send any alarms (hi coolant temp, etc) to the IPC (inst panel cluster) and HUD
The HVAC control module (center dash under radio) also ties into the computer data line system.
It's possible that you could have a Bad Engine coolant temperature sensor or wiring to or from the ECM. It's worth a check. Also, check the ground wire for good contact from the fan control module (on top of front frame rail)
The Engine coolant sensor has a tan and a yellow wire going to the ECM. If the temperature is above normal, the Dark green wire from the ECM triggers the fan speed through the RED/Orange Wire of the fan control module. The red wire that feeds the fan control module comes from the 60A fuse.
The Tan/Black and Tan from the ECM go to the Data system for alarms.
It's hard to imagine that the ECM is bad. Not likely. Pursue all other troubleshooting venues before even looking at replacing the ECM
I can send you the wiring diagrams (for all c6 systems by e-mail).
PM me your e-mal address and I'll sent it out ASAP.
The cooling fan system is on page 16 in the PDF file
Good Luck
Paul, you keep getting more impressive (and helpful) by the day.
What a great and informative breakdown...
In the wiring diagram below ( thanks @LV2TOUR ) I have overlaid some of my troubleshooting.
Blue Sections:
The upper blue section is where I confirmed the fuse looks good.
The lower blue section I am considering to be in good working order because of where I jumped power to it and confirmed the fans worked.
Orange Sections:
These seems to be the only places where I could have an issue based on the diagram.
I know the black/red wires going to the fuse block are wrapped up pretty tight, would you recommend I start at the fan and work my way to the fuse block? Or start at the fuse block and work my way to the fan?
Same question with the speed control wire as well?
Again thanks for all the help!
@bjones7131 -
As far as I know the cooling fans don't have a micro-relay, but I could be wrong?
Either place you start, it will be sometimes difficult to trace the wires in the wire loom. I would first check from the fan, looking for any breaks in the wires, etc.
Don't discount the wires from the Coolant temp sensor. Check those to be sure they are OK.
Good luck in your troubleshooting endeavours
There is no relay in this circuit
Applying 12v to speed control module red and orange wire fhould turn fan on to full speed. f this occurs, there is a break in this wire from PCM.
RUN a jumper from PCM to fan speed control module, if fans still do not work replace PCM.
Paul, you keep getting more impressive (and helpful) by the day.
What a great and informative breakdown...
Thank You. I'm just reading the schematics, and trying to be of some small help. Hopefully the OP can find the problem and fix it without too much trouble and not much $$
Funny story, my Vette got up to around 235 today while I was stuck idling. Got it home ok but the fan obviously wasn't coming on. I came inside and started doing research on the forum while it cooled off. I found these threads about the melted wiring harness and went to check it out. The connector looked fine. I reached in and touched the fan blade and it wouldn't turn. Great, the motor's frozen. I reached in and pushed a little harder on the blade and it moved with a scraping sound. After a few minutes of fishing around it turns out two tiny pebbles got into the fan shroud and wedged themselves between the bottom of the fan blade and the shroud keeping it from spinning. I got them out and drove it around verifying that the fan is working. I guess I got off lucky
06-13-2015, 07:39 PM
2005 C6 Cooling Fans Not Working
I reached in and pushed a little harder on the blade and it moved with a scraping sound. After a few minutes of fishing around it turns out two tiny pebbles got into the fan shroud and wedged themselves between the bottom of the fan blade and the shroud keeping it from spinning. I got them out and drove it around verifying that the fan is working. I guess I got off lucky 