Few A/C questions.

[lubbockguy1979]

That should work. On a refrigeration unit we typically set the fans to come on at 100-120 ambient temps. So for r12 probably aroind 150ish. The fan likely will only run while driving slow or at a traffic light. You might have to play with the temp setting also based of the size of the fan. If the fan is not large enough you might drop the temp further to get a head start. Id also wire in a toggle switch while your doing it incase of a tstat failure as well for a backup

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[meir]

That should work. On a refrigeration unit we typically set the fans to come on at 100-120 ambient temps. So for r12 probably aroind 150ish. The fan likely will only run while driving slow or at a traffic light. You might have to play with the temp setting also based of the size of the fan. If the fan is not large enough you might drop the temp further to get a head start. Id also wire in a toggle switch while your doing it incase of a tstat failure as well for a backup

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Thanks. That was very helpful.

 

[lubbockguy1979]

So.e one else might chime in but id think you might want the fan on a tad sooner then 150 degrees. These are what we typically use in various applications. They are simple open close contacts that use the refrigerant psi rise to trigger the fan. The bullet types are avalible in a wide rage of psi for different applications. The grey box is better quality and can be dialed in alot better

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[meir]

So the concept is to connect the pressure sensor to the high pressure line?
I think your idea with the temp sensor is not bad at all.
I drove the truck today to work, and also went on the highway at noon when temp was around 90. The ac was blowing very cold. I capt it on medium an two lines under the max cold.
Like you said, I need the fan only on high traffic or when stopped at lights. I can install the sensor, and adjust it by trail and error. The toggle switch is also a good idea, and while testing, I can add a temporary LED light to let me know when the fan is running, just in case I cannot hear it.

 

[lubbockguy1979]

Honestly psi is where you have the problems. The tempratures should follow unless you had a tremendous amount ot subcooling or the lack there of. The truck uses low psi to turn off on the low side to prevent freezing.

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[L31MaxExpress]

Honestly psi is where you have the problems. The tempratures should follow unless you had a tremendous amount ot subcooling or the lack there of. The truck uses low psi to turn off on the low side to prevent freezing.

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When I played with HC refrigerants I actually added a thermal cycling switch to the evaporator inlet pipe on my old G20 van. GM put them on late RWD 80s Cadillacs. I adjusted it until the evaporator inlet would just start to frost and it would cycle off to keep the evaporator from freezing. The pressure cycling switch could not have the cutout point raised high enough to keep the evaporator from freezing. I also added a fan to the condenser that used the a/c compressor signal and high blower fan relay input signal as power control for the fan. If a/c was on and the blower on high the 10" pusher ran. If the a/c cycled off or you went down in blower speed (less a/c demand)the fan turned off. I was able to do that with one relay added that controlled the relay running the fan.

 

[meir]

Well, took some measurements last night.
88F with 66% humidity ambient temperature , 42F while driving around town, 50F at idle. Thermometer directed to center vent, and the mix flap is open (fresh air). Electric fan is not connected yet.
Just for reference I drove my wife car (2017 Hyundai Veloster)
Lowest temperature reading at 38 with the mix flap close.
I think I’m pretty happy with the results.

 

[jdla140]

Some 96+ trucks had an e-fan on the front when they didn't have an external oil cooler. You could look into one of those and have a basically factory install. If I were you, I'd hook a relay up to the compressor's clutch wiring. That way the fan only runs when the compressor is on. On some newer cars the fan runs as long as AC is selected, I wouldn't worry too much about running the fan "too much", you can't really get the condenser too cold lol.

 

[meir]

Some 96+ trucks had an e-fan on the front when they didn't have an external oil cooler. You could look into one of those and have a basically factory install. If I were you, I'd hook a relay up to the compressor's clutch wiring. That way the fan only runs when the compressor is on. On some newer cars the fan runs as long as AC is selected, I wouldn't worry too much about running the fan "too much", you can't really get the condenser too cold lol.

yes. that was my first thought.
i already have the fan installed. not connected yet.
this is the one i got. didn't take a picture on the truck, but it fits perfectly.

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my first thought was to do as you say (and you are right. on my other cars the fan is always on if the AC is on), but connecting to a thermostat as other suggested is not a bad idea. less stress on the alternator and the fan.
probably will go with this one as it has a wide range of temperature selection i can experiment with.


https://shop.advanceautoparts.com/p...GKzqkXlLPf-Qu5__haEaAu36EALw_wcB&gclsrc=aw.ds

 

[lubbockguy1979]

Your right if it is extremely hot about direct wiring the fan although in mid temp operations when trying to dehumidify or defrost in low ambiet the fan might hurt performance

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