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Discussion Starter #1
i just installed the Classic Auto Air under dash AC unit. I have an electric radiator fan. Does this fan need to be on when the AC is on?

Allen
 

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Allen,
All the cars nowadays connect the fan with the AC compressor clutch, such that they not only come on with a set temperature of the coolant, but when the AC clicks on.
I'm sure it's because of the increased air flow thru the condenser, more than keeping temps down.
 

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Discussion Starter #5
I’ve emailed CAA. There are not instructions on how to wire it up. But I suspect connecting the blue wire to my Dakota Digital electric fan switch will be the way to go.
 

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I replaced the binary switch with a trinary switch from amazon, part number UAC SW 4082C. The black wires connect the same as the binary switch supplied with the kit. The blue wires are used to ground a relay and turn the fans on when the pressure in the system rises to a certain point. This way will help prevent unnecessary wear and tear on the fans by running them the whole time the AC is on. Her is an example of how to wire it.

748074
 

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The reason the fan needs to be on when the AC is on is the AC condenser is mounted in front of the radiator. The condenser removes the heat from the AC system. Since it is located in front of the radiator that heat goes right through the radiator core after it leaves the condenser. I looked up what that temperature is and found one source saying it is between 200F to 400F. I know its too hot to touch. You can imagine how much heat transfer ability is lost in your radiator core when the heat is transferred from the condenser to the air and then flows through the radiator core. You will also notice that all AC condensers are manufactured from aluminum because of its ability to transfer heat better. Then also look at the number of fins. The fins absorb the heat from the tubes and transfer it to the air. The more fins the more heat transfer. A lot of heat transfer is going on between the AC condenser and the air when the AC compressor is on.

You use to see signs along an incline to turn off your AC. You also so saw them out in the desert. Not so must because it put an extra load on the engine but because all that heat from the condenser was going through the radiator.

Modern cars will circulate the fan on and off using a coolant temperature switch usually located in the radiator. When you turn the AC it overrides the temp switch and turns the fan on full time.

What the condenser does.

 

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Discussion Starter #9
Thanks for all of the replies. I understand now. The binary switch that comes with the CAA system is a safeguard switch to prevent damage from either too low or too high pressures The trinary switch does the same but also has another function. It wires to your electric fan and turns it on when a certain pressure is reached (I’ve seen 240-258 listed).

The benefit of this is that your fan isn’t always running when the AC is on, only when a certain pressure threshold is reached. I’m assuming this is because below the theshold the fan isn’t needed and saves wear on the fan?

If so, is this a significant factor so I should take the binary switch off and it with a trinary switch?
 

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Thanks for all of the replies. I understand now. The binary switch that comes with the CAA system is a safeguard switch to prevent damage from either too low or too high pressures The trinary switch does the same but also has another function. It wires to your electric fan and turns it on when a certain pressure is reached (I’ve seen 240-258 listed).

The benefit of this is that your fan isn’t always running when the AC is on, only when a certain pressure threshold is reached. I’m assuming this is because below the theshold the fan isn’t needed and saves wear on the fan?

If so, is this a significant factor so I should take the binary switch off and it with a trinary switch?
Understand that i am a minimalist -- I learned that changing out the lugnuts on my Porsche to titanium ones (to decrease the unsprung weight) was actually STUPID for a street racer. BUT, it took me about 20 years to get to this point of understanding (I'm now 70).
If you keep chasing "a better idea", you will never get there, because SOMEONE always has a better theory or idea, no matter how insignificant an advantage it will attain. And car guys get caught up in trivial conundrums often for pseudoscientific reasons.

So, IF YOU ALREADY have a binary, just keep it! Face it, when you are going to be running your AC, it is going to be hot outside anyway, and your radiator will need the cooling anyway.
Just my point of view at this very minute, at the end of a hard day at work....
 

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Thanks for all of the replies. I understand now. The binary switch that comes with the CAA system is a safeguard switch to prevent damage from either too low or too high pressures The trinary switch does the same but also has another function. It wires to your electric fan and turns it on when a certain pressure is reached (I’ve seen 240-258 listed).

The benefit of this is that your fan isn’t always running when the AC is on, only when a certain pressure threshold is reached. I’m assuming this is because below the theshold the fan isn’t needed and saves wear on the fan?

If so, is this a significant factor so I should take the binary switch off and it with a trinary switch?
Correct, swap to the trinary switch and wire it to the ground trigger on your fan controller. The idea is the fan can be turned on by either the ground provided by the trinary switch, or the ground provided by the coolant temp sensor. This way you can let the fan controller decide if the fans need to run full time depending on coolant temps. If coolant temps are steady and there is plenty of airflow, such as cruising on the highway, there is no need for the fan to run. Doing so would only add extra wear and tear on the fan and electrical system.
 

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i just installed the Classic Auto Air under dash AC unit. I have an electric radiator fan. Does this fan need to be on when the AC is on?

Allen
Yes it needs to be on. If not the compressor will shut off when the pressure reaches the limit of the high pressure switch. Probably around 300 to 325 psi for 134a. Not good for the compressors life span.
Here is diagram for my flexalite system.
yarb
748209
 

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Discussion Starter #13
So, IF YOU ALREADY have a binary, just keep it! Face it, when you are going to be running your AC, it is going to be hot outside anyway, and your radiator will need the cooling anyway.
Just my point of view at this very minute, at the end of a hard day at work....


I agree with this point. Since the system is in and replacing the switch will involve removing the front of the car, and since the amount of time I will actually be using the AC is not huge, I don’t see the benefit being more than the cost. And as you state, most of the time I will be using the AC the fan will be running anyways due to the elevated environmental temperature.

Plus, if I end up being wrong, I can always change the switch later. With 3-5000 miles at most per year, and my need for AC not being much living in Seattle (Hot Rod Power Tour next year is the main reason I put it in) I don’t see having a binary switch putting too much work on the fan and electrical system.

Allen
 
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