should fans run below 30 mph?
Thread Starter
Le Mans Master
Joined: Sep 2004
Posts: 6,714
Likes: 6
From: Providence RI
should fans run below 30 mph?
I put a 180 stat in my 01'vert then adjusted the fans with a Predator hand-held unit. Seems like the fans are always on below a certain car speed. I can always here them running when I come to a stop. Is this normal or do the fans need to be adjusted upward? Coolant temps run between 194-198 all the time. Thanx.
Burning Brakes
Joined: Mar 2010
Posts: 960
Likes: 1
From: Trussville AL
I don't think speed has anything to do with it. The fan controller looks at temps. Your temps don't seem too bad. Just as a precaution have you cleaned your radiator and condenser? I'm not sure what temp the fans should be with you tstat.
Thread Starter
Le Mans Master
Joined: Sep 2004
Posts: 6,714
Likes: 6
From: Providence RI
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Team Owner
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From: Kannapolis NC
Even if you mistakenly reversed the setting you stated with what you actually set, you still need to raise the temps if you don't want the fans to run all the time at idle or slow speed. They're both going to run when you turn on the a/c at slower than 35mph anyway no matter what you set, so they don't need to be that low.
Last edited by 65GGvert; Nov 29, 2013 at 08:17 PM.
Thread Starter
Le Mans Master
Joined: Sep 2004
Posts: 6,714
Likes: 6
From: Providence RI
With the temp selections that you picked and the operating temp of the engine your fans WILL indeed be on all the time until the vehicle reaches 35MPH.
For Fan1 temps you selected ON at 184 and OFF at 193 a higher temp than the ON temp which is not correct.
For Fan2 temps you selected ON at 194 and OFF at 204. again a higher temp than the ON temp which is not correct.
I suspect that you don't understand what FAN1 and FAN2 relate to. YES, there are 2 fans in the car BUT they BOTH run in LOW speed mode and they BOTH run in HIGH speed mode.
FAN1 temps are the on and off temps for LOW speed mode and FAN2 temps are the on and off temps for HIGH speed mode.
Here is a wiring diagram for the fans:
If you know how to read wiring diagrams you will see that the fans are initially wired in series so that when the fans are commanded ON by the PCM at FAN1 temp (PCM isthe fan controller for the C5) the fans will have about 6 volts dropped across each motor so they each run at a "lower than possible speed". When the temp reaches the FAN2 ON temp the wiring to the fans is switched to parallel so that each fan has a full 12 volts (or what ever actual battery voltage is) across it and they will run at a faster speed.
The OFF temp of Fan1 setting needs to be LOWER than the ON temp. Using the GM Factory settings as a basis for setting fan temp differentials, the FAN2 ON temp should be about 9 degrees higher than the FAN1 on temp and the FAN2 OFF temp should be the same as the FAN 1 ON temp. That leaves the FAN1 OFF temp. It should be set so that it is HIGHER than the normal operating temp of the car to avoid continuous running of the fans. The fans will have a very short life if they run all the time.
I have a 170 T'stat in my car and the FAN1 on temp is about 206 and FAN1 OFF temp is 200. My FAN2 ON temp is 216 and FAN2 OFF temp is 206. My normal operating temp is about 190.
This is NOT correct. The fan controller on the C5 is the PCM and it does indeed use speed to command the fans OFF. Once the vehicle speed reaches 35MPH the fans are commanded OFF irrespective of engine temp. Air flow through the radiator is apparently better with the fans free wheeling than with them running and I suspect that's why GM engineers did that.
For Fan1 temps you selected ON at 184 and OFF at 193 a higher temp than the ON temp which is not correct.
For Fan2 temps you selected ON at 194 and OFF at 204. again a higher temp than the ON temp which is not correct.
I suspect that you don't understand what FAN1 and FAN2 relate to. YES, there are 2 fans in the car BUT they BOTH run in LOW speed mode and they BOTH run in HIGH speed mode.
FAN1 temps are the on and off temps for LOW speed mode and FAN2 temps are the on and off temps for HIGH speed mode.
Here is a wiring diagram for the fans:
If you know how to read wiring diagrams you will see that the fans are initially wired in series so that when the fans are commanded ON by the PCM at FAN1 temp (PCM isthe fan controller for the C5) the fans will have about 6 volts dropped across each motor so they each run at a "lower than possible speed". When the temp reaches the FAN2 ON temp the wiring to the fans is switched to parallel so that each fan has a full 12 volts (or what ever actual battery voltage is) across it and they will run at a faster speed.
The OFF temp of Fan1 setting needs to be LOWER than the ON temp. Using the GM Factory settings as a basis for setting fan temp differentials, the FAN2 ON temp should be about 9 degrees higher than the FAN1 on temp and the FAN2 OFF temp should be the same as the FAN 1 ON temp. That leaves the FAN1 OFF temp. It should be set so that it is HIGHER than the normal operating temp of the car to avoid continuous running of the fans. The fans will have a very short life if they run all the time.
I have a 170 T'stat in my car and the FAN1 on temp is about 206 and FAN1 OFF temp is 200. My FAN2 ON temp is 216 and FAN2 OFF temp is 206. My normal operating temp is about 190.
This is NOT correct. The fan controller on the C5 is the PCM and it does indeed use speed to command the fans OFF. Once the vehicle speed reaches 35MPH the fans are commanded OFF irrespective of engine temp. Air flow through the radiator is apparently better with the fans free wheeling than with them running and I suspect that's why GM engineers did that.
I'll try your settings which should work with my 180 stat.