Electric Fans - A/C Signal
06-10-2005, 08:58 PM
#1
Electric Fans - A/C Signal
Sorry this is gonna be a long post. 
Been many posts on the subject. Controlling twin electric fans with the Pre-05 Truck PCMS and aftermarket wiring harnesses.
Current setup works like this.
1> PCM sees Set ON temp and both fans come on low via pin 42.
2> If PCM both fans low and the A/C clutch cycles both fans go to high.
3> Coolant below SET On temp and A/C cycles just one fan goes to high.
Problem I have. Doesn't bother all. Is my fan coming on cruising down the highway at speed, anytime the darn A/C clutch cycles. Puts a drag on the engine that I can feel and at night it flickers the headlights. I've already installed a 145 amp alt. hoping to help the light flicker. It didn't. You need air flow accross the A/C condensor at a stop for the good cooling but you don't somewhere above 20mph I'm guessing.
I've been trying to find a thermostat controlled switch to connect in series with the A/C clutch circuit so that only when the condenser is hot enough would the fan come on. Shouldn't happen when moving down the road. Problem is I don't know what that temp is and can't find a good thermostat to try. Thought about some kind of rigged speed sensor and can't find anything there that works.
Had a brain fart tonight and though how about hooking a relay to the brake light circuit. Instead of sensing when moving do the reverse and sense when stopped or slowing. Have the fan come on with the A/C when you have your foot on the brake, like you would sitting in traffic. Not perfect but would be better I think and a simple improvement.
Thoughts
Been many posts on the subject. Controlling twin electric fans with the Pre-05 Truck PCMS and aftermarket wiring harnesses.
Current setup works like this.
1> PCM sees Set ON temp and both fans come on low via pin 42.
2> If PCM both fans low and the A/C clutch cycles both fans go to high.
3> Coolant below SET On temp and A/C cycles just one fan goes to high.
Problem I have. Doesn't bother all. Is my fan coming on cruising down the highway at speed, anytime the darn A/C clutch cycles. Puts a drag on the engine that I can feel and at night it flickers the headlights. I've already installed a 145 amp alt. hoping to help the light flicker. It didn't. You need air flow accross the A/C condensor at a stop for the good cooling but you don't somewhere above 20mph I'm guessing.
I've been trying to find a thermostat controlled switch to connect in series with the A/C clutch circuit so that only when the condenser is hot enough would the fan come on. Shouldn't happen when moving down the road. Problem is I don't know what that temp is and can't find a good thermostat to try. Thought about some kind of rigged speed sensor and can't find anything there that works.
Had a brain fart tonight and though how about hooking a relay to the brake light circuit. Instead of sensing when moving do the reverse and sense when stopped or slowing. Have the fan come on with the A/C when you have your foot on the brake, like you would sitting in traffic. Not perfect but would be better I think and a simple improvement.
Thoughts
06-11-2005, 06:09 AM
#2
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Originally Posted by KySilverado
Sorry this is gonna be a long post.
Been many posts on the subject. Controlling twin electric fans with the Pre-05 Truck PCMS and aftermarket wiring harnesses.
Current setup works like this.
1> PCM sees Set ON temp and both fans come on low via pin 42.
2> If PCM both fans low and the A/C clutch cycles both fans go to high.
3> Coolant below SET On temp and A/C cycles just one fan goes to high.
Problem I have. Doesn't bother all. Is my fan coming on cruising down the highway at speed, anytime the darn A/C clutch cycles. Puts a drag on the engine that I can feel and at night it flickers the headlights. I've already installed a 145 amp alt. hoping to help the light flicker. It didn't. You need air flow accross the A/C condensor at a stop for the good cooling but you don't somewhere above 20mph I'm guessing.
I've been trying to find a thermostat controlled switch to connect in series with the A/C clutch circuit so that only when the condenser is hot enough would the fan come on. Shouldn't happen when moving down the road. Problem is I don't know what that temp is and can't find a good thermostat to try. Thought about some kind of rigged speed sensor and can't find anything there that works.
Had a brain fart tonight and though how about hooking a relay to the brake light circuit. Instead of sensing when moving do the reverse and sense when stopped or slowing. Have the fan come on with the A/C when you have your foot on the brake, like you would sitting in traffic. Not perfect but would be better I think and a simple improvement.
Thoughts
Been many posts on the subject. Controlling twin electric fans with the Pre-05 Truck PCMS and aftermarket wiring harnesses.
Current setup works like this.
1> PCM sees Set ON temp and both fans come on low via pin 42.
2> If PCM both fans low and the A/C clutch cycles both fans go to high.
3> Coolant below SET On temp and A/C cycles just one fan goes to high.
Problem I have. Doesn't bother all. Is my fan coming on cruising down the highway at speed, anytime the darn A/C clutch cycles. Puts a drag on the engine that I can feel and at night it flickers the headlights. I've already installed a 145 amp alt. hoping to help the light flicker. It didn't. You need air flow accross the A/C condensor at a stop for the good cooling but you don't somewhere above 20mph I'm guessing.
I've been trying to find a thermostat controlled switch to connect in series with the A/C clutch circuit so that only when the condenser is hot enough would the fan come on. Shouldn't happen when moving down the road. Problem is I don't know what that temp is and can't find a good thermostat to try. Thought about some kind of rigged speed sensor and can't find anything there that works.
Had a brain fart tonight and though how about hooking a relay to the brake light circuit. Instead of sensing when moving do the reverse and sense when stopped or slowing. Have the fan come on with the A/C when you have your foot on the brake, like you would sitting in traffic. Not perfect but would be better I think and a simple improvement.
Thoughts
06-11-2005, 07:44 AM
#3
what i did is run a wire inside.
the wire that goes to the a/c signal wire--i ran thru a relay. then to a lighted switch inside the cab. when i was running in traffic around town i left this switch off. so the a/c would trigger the fans. as soon as i got on the freeway i turned on the switch that took away the a/c signal. hell as long as you are moving airflow thru the rad will be enough to cool everything. when i was on the freeway they never came on.
85--switched power-from the switch.
86-ground.
30-from the a/c signal wire.
87A-to the fan relays.
87-leave open.
87a is the terminal that is normally closed. so when the relay is activated it will take away continuity from this terminal.
the wire that goes to the a/c signal wire--i ran thru a relay. then to a lighted switch inside the cab. when i was running in traffic around town i left this switch off. so the a/c would trigger the fans. as soon as i got on the freeway i turned on the switch that took away the a/c signal. hell as long as you are moving airflow thru the rad will be enough to cool everything. when i was on the freeway they never came on.
85--switched power-from the switch.
86-ground.
30-from the a/c signal wire.
87A-to the fan relays.
87-leave open.
87a is the terminal that is normally closed. so when the relay is activated it will take away continuity from this terminal.
06-11-2005, 07:49 AM
#4
Originally Posted by L82gofast
Thats not a brain fart, that's a good idea. Kind of a if, then, else loop. Just another relay triggered off of the brake in series with the AC fan relay should work.
After thinking more about the relay to the brake light circuit, I think a timer relay with about a 5 second delay would fit the bill nicely. Wouldn't start or stop the fan unless you've had you foot on the brake for 5 seconds. Doubt they even make one in 12V?
Hell a cheap small programmable controller with couple inputs and outputs is sounding good.
06-11-2005, 07:57 AM
#5
well if it is off the brake it will still wont allow the fans to run when in slow moving traffic if the brake is not pushed therefore not letting iot cool the condensor. the relay thing i did is just a simple way to keep the wiring and less moving or electrical parts down to a minimum. i suppose if you were going to get technical. a speed sensitive switch could be used. some kind of switch as a a lever activated switch. then put on a piece of aluminum or other metal that is enough to keep the switch open at low speeds but when you speed up it is enough to catch the wind and close the switch.
06-11-2005, 08:03 AM
#7
http://i17.ebayimg.com/03/i/03/ea/bc/f8_1_b.JPG
use this type switch. then on the end figure out what size piece of metal or whatever will activate it at a certain speed.
use this type switch. then on the end figure out what size piece of metal or whatever will activate it at a certain speed.
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06-11-2005, 08:32 AM
#8
Originally Posted by 02denali
http://i17.ebayimg.com/03/i/03/ea/bc/f8_1_b.JPG
use this type switch. then on the end figure out what size piece of metal or whatever will activate it at a certain speed.
use this type switch. then on the end figure out what size piece of metal or whatever will activate it at a certain speed.
Concerned about windy days and how large a sail to make the switch....getting the right sensitivity. Thinking I will try this more so than the brake idea now after thinking about the delay needed there.Know I could just run a manual switch into the cab. Kinda makes it to easy and I would forget to turn the dang thing on.
