cooling fan again not coming on
02-14-2006, 09:41 AM
#1
Racer
Thread Starter
cooling fan again not coming on
He i posted a week ago about my cooling fan not coming on at highspeed. The cooling fan only comes on at low speed with the air on. When air is off the fan does not come on and it begins to run hot of course. I checked the fuses. All good. SOmeone helped me here with the relay schematic and I replaced all 3 relays and still no high speed fan.
I showed my mechanic and he didnt have time to fix it but said it is probably the cooling sensor. He thinks there is 2 oon the car. Im not sucre..Can someone tell me where it is? Would this cause the fan to not come on high or work intermittently? Last week it came on when it was sitting running 1 time. Now nothing. I did find something that looked like a sensor oon the engine head on the drivers side front near the exhaust manifold, but not sure if this is a coolant sensor. I unplugged it when the car was running and the engine shut off. Plugged it back in and car started but still no fan...Any help?
Also my car has 27,000 miles on it and is a 2000. Are there any factory service inverals I am supposed to be doing? The guy I bought it from had no receipts to give me or a owners manual. Thanks for all help on both questions!
I showed my mechanic and he didnt have time to fix it but said it is probably the cooling sensor. He thinks there is 2 oon the car. Im not sucre..Can someone tell me where it is? Would this cause the fan to not come on high or work intermittently? Last week it came on when it was sitting running 1 time. Now nothing. I did find something that looked like a sensor oon the engine head on the drivers side front near the exhaust manifold, but not sure if this is a coolant sensor. I unplugged it when the car was running and the engine shut off. Plugged it back in and car started but still no fan...Any help?
Also my car has 27,000 miles on it and is a 2000. Are there any factory service inverals I am supposed to be doing? The guy I bought it from had no receipts to give me or a owners manual. Thanks for all help on both questions!
02-15-2006, 09:06 AM
#3
Melting Slicks
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The C-5 has it's own on-board diagnostic display in the "DIC" display
in the instrument panel. You don't need a "plug-in" device to read them...... the car displays them for you. Run a search on this forum to find out how to access the codes. Don't be fooling around pulling wires at random.
The codes will tell for sure if the coolant sensor is dead.
In the meantime, keep the A/C on..... that will run the fans, as you already noticed.
I installed an "on-off" switch to manually turn on the fans.
in the instrument panel. You don't need a "plug-in" device to read them...... the car displays them for you. Run a search on this forum to find out how to access the codes. Don't be fooling around pulling wires at random.
The codes will tell for sure if the coolant sensor is dead.
In the meantime, keep the A/C on..... that will run the fans, as you already noticed.
I installed an "on-off" switch to manually turn on the fans.
02-15-2006, 02:07 PM
#4
Racer
Thread Starter
hmm on off switch? Thats taking a risk....Someone will forget to turn the switch on and burn up your car. Especially if you valet it. I dont wanna jerry-rig it especially with 27k on it. My DIC is showing no codes I checked it.... Anyone know where the coolant sensors are located in the engine? I think I shorted it or them out after I steam cleaned my engine 
Thanks
Thanks
02-15-2006, 11:38 PM
#7
Burning Brakes
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I dont know why youre not showing any codes, especially if the fans arent working.
As to why the engine dies is because that sensor interacts with the fuel system. When the car starts to overheat, the pcm will shut off 4 cylinders to help the engine cool and it does that by killing 4 fuel injectors. Anyway, it needs that sensor in order to make that determination.
Your situation should be easy to figure out. But you need to make 100% sure of your status. As long as your year vette operates the same as mine, 2002, then both fans operate at the same time. Either both are at high speed or both at low speed. When you stated that they operate at low speed with the a/c on, are BOTH fans running and are you sure its low speed?
As to why the engine dies is because that sensor interacts with the fuel system. When the car starts to overheat, the pcm will shut off 4 cylinders to help the engine cool and it does that by killing 4 fuel injectors. Anyway, it needs that sensor in order to make that determination.
Your situation should be easy to figure out. But you need to make 100% sure of your status. As long as your year vette operates the same as mine, 2002, then both fans operate at the same time. Either both are at high speed or both at low speed. When you stated that they operate at low speed with the a/c on, are BOTH fans running and are you sure its low speed?
02-16-2006, 04:32 PM
#9
Racer
Thread Starter
yes both are on and both are on low speed with a/c on. Other than that I dot know what else it could be. I washed my engine last week and then this happened. Only low fan speed is coming on now. I replaced the relays and this did nothing. The high speed fans did come one one night after coming home from a restaurant when the guage got to the normal 180 or so but it has not come on since then. Now it is getting over 200 and i look at the fans and nothing is on. When i click the ac on, then and only do the fans come on low speed
Damn ive had this car 3 weeks! This is y 3rd c5 and all I have had is problems with all of the. Steering column lockups, passengar side ac temp not working in all 3 vettes, seats rocking due to the tracks wearing out with low miles, my "pull key and wait 10 secs" happened in all 3 cars, and still happening with this one with 27000 miles on it. Now my damn gas guage is dropping to "E" after reading half tank when I park it. I have read the fixes but you would thing GM in this day of age, could rectify all these problems since they had 3 years to fix them (97-my 2000).
I gave up a boxster for this vette and Im thinking I made a mistake.
How can GM consider this "the heartbeat of america" when all these cars have done for me is cause heartache and breakdowns, after paying $25,000 cash. I just understand why they wont recall all these damn things that are common with all vette owners
Anyway sorry to sound distraught but I am so sick of all the same damn problems with everyones c5 corvettes. I appreciate everyones help on the cooling fans. I still dont kow what to do from here.
Next month (i hope not) i will be posting something saying "my car wont start now", and I have less miles than most people do with a 2004/2005
Damn ive had this car 3 weeks! This is y 3rd c5 and all I have had is problems with all of the. Steering column lockups, passengar side ac temp not working in all 3 vettes, seats rocking due to the tracks wearing out with low miles, my "pull key and wait 10 secs" happened in all 3 cars, and still happening with this one with 27000 miles on it. Now my damn gas guage is dropping to "E" after reading half tank when I park it. I have read the fixes but you would thing GM in this day of age, could rectify all these problems since they had 3 years to fix them (97-my 2000).
I gave up a boxster for this vette and Im thinking I made a mistake.
How can GM consider this "the heartbeat of america" when all these cars have done for me is cause heartache and breakdowns, after paying $25,000 cash. I just understand why they wont recall all these damn things that are common with all vette owners
Anyway sorry to sound distraught but I am so sick of all the same damn problems with everyones c5 corvettes. I appreciate everyones help on the cooling fans. I still dont kow what to do from here.
Next month (i hope not) i will be posting something saying "my car wont start now", and I have less miles than most people do with a 2004/2005
02-16-2006, 05:12 PM
#10
Burning Brakes
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The high speed fans wont come until well above 200. Do you have the stock fan programming? Whats the hottest youve let the engine get? Let the engine get up to around 238 with the a/c off and see if the high speed fans come on then. If the engine temp gets to 240 and the high speed fans still havent come on, and you say you checked all 3 fuses and they are good, and you replaced all 3 relays and are sure they are installed correctly, and if both fans run during low speed, then I would say that either your pcm is bad or the wire that comes from the pcm and goes to relay 43 and 44 is open. The ground G102 shouldnt be a problem because the fans are working in low speed.
02-17-2006, 12:40 PM
#11
Racer
Thread Starter
Thanks for the info av8tr and no offence, but I tend to differ on the temperature the fans come on. I have had 3 c4s and 3 c5s in the past. Everyone of them came on 2 lines before the 200 mark. They were all original and not tampered with and original thermostats. No mods anywhere.I know my car and for the first 3 weeks I had it (about 2 months ago)the fans came on high speed like normal at 185 or 2 lines before the middle... I washed my engine lighty with a sprayer and then the fan thing happens. The car has only 27,000. Its like brand new so I doubt the pcm is bad. Someone told me that if the coolant sensor is bad or shorted the fans wont come on...Does this sound right? Someone actually told me on here, to install an on and off switch, lol, I dont think I will do this in a 200 corvette that was just bought for $25,000.
Has anyone else had this problem with the fans?
My car has gotten up to about 230 and no fans come on. I have to put the a/c on just to get the car to cool down with fans on low. Again, sometimes maybe 1 time every 2 weeks, the fans will come on high at 180/185 for about 15 seconds, shut off, then come on high again ect, and cycle as normal.
As of 2 weeks ago they do not come on high anymore
Has anyone else had this problem with the fans?
My car has gotten up to about 230 and no fans come on. I have to put the a/c on just to get the car to cool down with fans on low. Again, sometimes maybe 1 time every 2 weeks, the fans will come on high at 180/185 for about 15 seconds, shut off, then come on high again ect, and cycle as normal.
As of 2 weeks ago they do not come on high anymore
02-17-2006, 02:34 PM
#12
Burning Brakes
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Ok. No offense but you can beg to differ all you like. The fact is that the fan temps, if factory settings havent been tampered with in the PCM, are set to:
Low speed on 226
Low speed off 219
High speed on 235
High speed off 226.
Your year may differ slightly but that should be a pretty good ballpark of temperature operations.
Now, you say your fans come on at high speed around 185. They shouldnt even be on at all at that temp if your A/C is off. If you bought the car used, how do you know the fan settings havent been changed? If the fans are coming on like you say, then someone has been into the PCM and adjusted the fan settings. Also, the PCM is what controls the fans and it gets its temp readings from the temp sensor in the drivers side head. If youre analog temp gauge and DIC are showing temps, then I would think the temp sensor is working.
Now, you say the fans come on at low speed when the A/C is on, that confirms that the low speed circuit is good.
I think you need to find someone with LS1 edit and check the PCM's fan settings or go to the dealership and have them put a Tech 2 on it and they can do the full operation and cycle the fans and that will tell you for sure if its working correctly. Or if youre any good with schematics, you can use the pic of the wiring for the fans thats on your other thread and troubleshoot it. When looking at that schematic, you see the low and high speed ground wires that comes from the PCM which grounds the relays to operate the fans. Find those wires in the fuse/relay box and ground them, with the key in the on position, both fans should go to high speed mode. If they work fine at that point, then its either the PCM or a break in those ground wires.
Low speed on 226
Low speed off 219
High speed on 235
High speed off 226.
Your year may differ slightly but that should be a pretty good ballpark of temperature operations.
Now, you say your fans come on at high speed around 185. They shouldnt even be on at all at that temp if your A/C is off. If you bought the car used, how do you know the fan settings havent been changed? If the fans are coming on like you say, then someone has been into the PCM and adjusted the fan settings. Also, the PCM is what controls the fans and it gets its temp readings from the temp sensor in the drivers side head. If youre analog temp gauge and DIC are showing temps, then I would think the temp sensor is working.
Now, you say the fans come on at low speed when the A/C is on, that confirms that the low speed circuit is good.
I think you need to find someone with LS1 edit and check the PCM's fan settings or go to the dealership and have them put a Tech 2 on it and they can do the full operation and cycle the fans and that will tell you for sure if its working correctly. Or if youre any good with schematics, you can use the pic of the wiring for the fans thats on your other thread and troubleshoot it. When looking at that schematic, you see the low and high speed ground wires that comes from the PCM which grounds the relays to operate the fans. Find those wires in the fuse/relay box and ground them, with the key in the on position, both fans should go to high speed mode. If they work fine at that point, then its either the PCM or a break in those ground wires.
02-23-2006, 09:56 AM
#13
Racer
Thread Starter
Well guys...last night the high speed fans came on mysteriously by themselves at the temperature they have always come on.....1-2 lines before the middle of the guage (220). I think this is about 185/190 degrees or so. I cant figure this out. No there are no loose connections. I washed the engine about 3-4 weeks ago and they suddenly come on intermittently now...Sometimes the car goes to 235 and no fan comes on...I dont get it.....Any suggestions? I replaced the relays, and the temp sensor seems to be performing good because I am not getting any warning codes on the dic or check engine lights 
02-23-2006, 10:18 AM
#14
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St. Jude Donor '03-'04
I have p[osted this many times... before you think you have a problem, you should fully understand how the cooling system works....
here is some information you may find useful.
Depending on the model year...
For later model years:2001-2004
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph). The fans do not run above 35 mph ( 56 kph ) unless the ac is turned on and the coolant temp is at 85°C (185°F).
For early model years:
Low speed fans come on at 219,high speed fans come on at 228,low speed with a/c on...
here is some information you may find useful.
Depending on the model year...
For later model years:2001-2004
The low speed cooling fan is commanded on when the coolant temperature reaches 108°C (226°F). It is turned off if the coolant temperature lowers to 104°C (219°F). The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F). It is turned off if the coolant temperature lowers to 108°C (226°F). When the A/C is on and the coolant temperature reaches 85°C (185°F), the low speed cooling fan will be turned on at vehicle speeds less than 56 kPh (35 mph). The fans do not run above 35 mph ( 56 kph ) unless the ac is turned on and the coolant temp is at 85°C (185°F).
For early model years:
Low speed fans come on at 219,high speed fans come on at 228,low speed with a/c on...
02-23-2006, 09:36 PM
#15
Tech Contributor
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You may not have a problem. There are a number of variables that determine fan speed. The cooling fans do not always come on at high speed when the A/C is turned on. The A/C head pressure controls when the secondary fan speed is selected. To determine if they are working correctly you will need a schematic and the ability to analyze/debug an electrical circuit if need be. First I would read how the fans are supposed to work and verify for sure that they are not working correctly. Some of your variables change with your local environment.
Here is a description of how the fan circuit works from the 1997 Service Manual:
The electric cooling fan(s) are controlled by the PCM based on various inputs. Ignition voltage is supplied to all 3 cooling fan relays. The PCM controls relay number 1 by providing a ground path and controls relays number 2 and 3 by providing a separate ground path for those relays. The relay(s) are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected in series through cooling fan relay #3, while cooling fan relay #2 is open. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operate at high speed.
The PCM will also enable the cooling fans after the ignition is turned off. When the engine coolant temperature exceeds 140o C (284o F) and the ignition is turned off, the cooling fans will be enabled on low speed.
Low Speed Cooling Fans
The low speed cooling fans are controlled by the PCM based on the following inputs:
• The A/C system
• The Engine Coolant Temperature (ECT) sensor
• The Vehicle Speed Sensor (VSS).
The PCM will turn the low speed cooling fans ON when any of the following conditions exist at idle:
• Certain PCM Diagnostic Trouble Codes (DTCs) are set.
• ECT above 104oC (219oF) will enable low speed fans.
• A/C head pressure above 219 psi.
Once the low speed fans are turned ON by Engine Coolant Temperature, the PCM will turn the fans OFF when that temperature has dropped about 6o C (11oF). If the low speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 150 psi. The minimum ON time for the low speed cooling fans is 50 seconds.
When engine speed is above 3500 RPM for 12 seconds and the engine oil temperature is above 127o C (261o F), the low speed cooling fans will be turned ON.
High Speed Cooling Fans
The High Speed Cooling Fans are controlled by the PCM based on the following inputs:
•The A/C system
•The Engine Coolant Temperature (ECT) sensor
•The Vehicle Speed Sensor (VSS).
The PCM will turn the secondary cooling fan ON when any of the following conditions exist at idle:
• Certain PCM Diagnostic Trouble Codes (DTCs) set.
• ECT above 10goC (228oF).
• A/C head pressure above 225 psi.
Once the high speed cooling fans are turned ON by the Engine coolant temperature, the PCM will turn the fans OFF when that temperature has dropped about 6o C (11o F). If the high speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 180 psi. The minimum ON time for the high speed cooling fans is 26 seconds.
The driver side of the cooling fan relays (Coil side of relay) are diagnosed using DTCs P0480 and P0481.
Don't blame the car immediately it may be you who is screwed up.
Bill
Here is a description of how the fan circuit works from the 1997 Service Manual:
The electric cooling fan(s) are controlled by the PCM based on various inputs. Ignition voltage is supplied to all 3 cooling fan relays. The PCM controls relay number 1 by providing a ground path and controls relays number 2 and 3 by providing a separate ground path for those relays. The relay(s) are used to control the high current flow to power the cooling fan motors. Both fans operate together. When minimum cooling is required, the PCM energizes cooling fan relay #1 and both fans operate at low speed, since the fans are connected in series through cooling fan relay #3, while cooling fan relay #2 is open. When maximum cooling is required, the PCM energizes all three cooling fan relays. The left fan is still powered through cooling fan relay #1, but is now grounded through cooling fan relay #3. The right fan is now powered directly through cooling fan relay #2 and both fans operate at high speed.
The PCM will also enable the cooling fans after the ignition is turned off. When the engine coolant temperature exceeds 140o C (284o F) and the ignition is turned off, the cooling fans will be enabled on low speed.
Low Speed Cooling Fans
The low speed cooling fans are controlled by the PCM based on the following inputs:
• The A/C system
• The Engine Coolant Temperature (ECT) sensor
• The Vehicle Speed Sensor (VSS).
The PCM will turn the low speed cooling fans ON when any of the following conditions exist at idle:
• Certain PCM Diagnostic Trouble Codes (DTCs) are set.
• ECT above 104oC (219oF) will enable low speed fans.
• A/C head pressure above 219 psi.
Once the low speed fans are turned ON by Engine Coolant Temperature, the PCM will turn the fans OFF when that temperature has dropped about 6o C (11oF). If the low speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 150 psi. The minimum ON time for the low speed cooling fans is 50 seconds.
When engine speed is above 3500 RPM for 12 seconds and the engine oil temperature is above 127o C (261o F), the low speed cooling fans will be turned ON.
High Speed Cooling Fans
The High Speed Cooling Fans are controlled by the PCM based on the following inputs:
•The A/C system
•The Engine Coolant Temperature (ECT) sensor
•The Vehicle Speed Sensor (VSS).
The PCM will turn the secondary cooling fan ON when any of the following conditions exist at idle:
• Certain PCM Diagnostic Trouble Codes (DTCs) set.
• ECT above 10goC (228oF).
• A/C head pressure above 225 psi.
Once the high speed cooling fans are turned ON by the Engine coolant temperature, the PCM will turn the fans OFF when that temperature has dropped about 6o C (11o F). If the high speed cooling fans are turned ON by high A/C head pressure, the PCM will turn the fans OFF when the pressure has dropped to 180 psi. The minimum ON time for the high speed cooling fans is 26 seconds.
The driver side of the cooling fan relays (Coil side of relay) are diagnosed using DTCs P0480 and P0481.
Don't blame the car immediately it may be you who is screwed up.
Bill
02-24-2006, 10:21 AM
#16
Racer
Thread Starter
Bill...
It may be me that is screwed up? Wow thanks a lot for the positive cutdown. I am not "screwed up" as u so implied. All I asked is why my fans came on all the time when the temp came 2 lines before the 220 (half way on guage) all the time when car is sitting, with ac on or not, and now its not! I didnt do anything or screw anything up. All i did was wash my car and all of a sudden my high speed fans stopped coming on at the temperature they always came on at. I can actually smell a burning of antifreeze because they are not coming on...Ive had 3-4 c5s and every one of them came on at the spot where the 2 lines are before the 220. Now the car is getting to 3/4 hot when sitting, but sometimes by a ghostly occurance, they decide to come on at the 2 lines before mid guage (220). Next time I wont ask you Bill for your help if you have to try to beat me down because of a problem I am having with my cooling sysyem. My car has begun to overheat, but sometimes they magically start working at around 185 degrees (yes the high ones). If I knew I was going to get a crass remark I would have never posted this question here...All others thanks for the response...I wasnt blaming my car at all...I was just stating the facts of what has happened and what all my c5s in the past....Maybe Bill, your day was "screwed up" and you decided to throw a digger at me...No reply needed. Thank You
It may be me that is screwed up? Wow thanks a lot for the positive cutdown. I am not "screwed up" as u so implied. All I asked is why my fans came on all the time when the temp came 2 lines before the 220 (half way on guage) all the time when car is sitting, with ac on or not, and now its not! I didnt do anything or screw anything up. All i did was wash my car and all of a sudden my high speed fans stopped coming on at the temperature they always came on at. I can actually smell a burning of antifreeze because they are not coming on...Ive had 3-4 c5s and every one of them came on at the spot where the 2 lines are before the 220. Now the car is getting to 3/4 hot when sitting, but sometimes by a ghostly occurance, they decide to come on at the 2 lines before mid guage (220). Next time I wont ask you Bill for your help if you have to try to beat me down because of a problem I am having with my cooling sysyem. My car has begun to overheat, but sometimes they magically start working at around 185 degrees (yes the high ones). If I knew I was going to get a crass remark I would have never posted this question here...All others thanks for the response...I wasnt blaming my car at all...I was just stating the facts of what has happened and what all my c5s in the past....Maybe Bill, your day was "screwed up" and you decided to throw a digger at me...No reply needed. Thank You
02-24-2006, 11:08 AM
#17
Team Owner
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St. Jude Donor '03-'04
Here is some input from another Bill....
You need to read!!!!!
The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F).
I have posted this many times and I dont care how many C5 you have , My name is on everyone of the 1/4 million that were produced.
The high speed fans will not come on at a below 220 F unless your PCM has been reprogramed by a non GM service facility. This is of course with out the ac on. BTW both fans have high and low speed capability.
You need to read!!!!!
The high speed cooling fan is commanded on when the coolant temperature reaches 113°C (235°F).
I have posted this many times and I dont care how many C5 you have , My name is on everyone of the 1/4 million that were produced.
The high speed fans will not come on at a below 220 F unless your PCM has been reprogramed by a non GM service facility. This is of course with out the ac on. BTW both fans have high and low speed capability.
Last edited by Evil-Twin; 02-24-2006 at 11:11 AM.
