Please suggest fan on/off low/hi temp settings

[anguilla1980]

I have a giant single electric puller fan that I'm getting ready to install, it's 2 speed capable (low/hi). I have a 195f thermostat. Where I live gets upwards of 120f in the summer, last week it was already 104f. I have a VintageAir system that I'll be wiring so it kicks the fan into high anytime I turn my A/C on. I'll also be setting the fan to run for 60 seconds after I shut the engine off. At some point when I buy an electric water pump I'll set that to run with it after shutdown, my engine temp goes up 40 degrees just in the time it takes me to fill my tank and grab a drink.

Based on a 195f thermostat, what would be an optimal temperature to set for the fan turning ON in LOW? Then what's a good temp to have it kick into HIGH? I'm *thinking* 205f for LOW, then 220f for HIGH. Then what temperature for the fan to shut off? I'm thinking 200, seems to me I want the fan cycling, not alway on right?

I asked this on a couple other forums and instead of people replying with their suggested temp settings, the thread turned into a discussion of others about the merits of electric fan vs mechanical lol. Please don't do that here, I really just need some no B.S. solid suggestions based on actual experience.

Thanks! Alex

[dontlifttoshift]

Use a trinary switch so that the fan runs based on AC pressure. Which car is this? How are you controlling the fans?

I would say you are on the right track with the low speed but I would probably bring the high speed in at 215* and shut high off at 208*.

The reality of it is that every car is different and I try to set the fans so that high speed or the second fan doesn't engage during "normal" operation.....that leaves me some reserve. Sometimes that doesn't work and low speed runs pretty much all the time and high speed cycles on/off.

[anguilla1980]

Thanks for the info. I hadn't thought about the high shut off temp.


This is the controller I purchased, as I already have the Dakota Digital guages and sensors for it to tie into:

https://www.summitracing.com/parts/dak-pac-2750

It didn't come with an A/C relay, is that needed or do I just run some signal wire from my VintageAir system to it?

[dontlifttoshift]

Not a relay, a Trinary switch.


This replaces the Binary Hi/Lo pressure safety switch that you already have in your AC system, adding a third function, fan control.

The Dakota controller wants a 12v input on the AC terminal to operate the fans, so you will run a 12v wire to a blue wire on the trinary switch and then the other blue wire will run back to the AC terminal on the PAC-2750. When high side pressure reaches 254 psi, the switch closes and signals the PAC-2750 to turn the fan on. I think it shuts off when pressure drops below 150 psi.

The two Black/Green wires connect to your system just like your Binary switch does now.

[anguilla1980]

That sounds great but I'm not looking to make any changes that require me to evacuate my A/C system to install it. I'm a DIY guy on a very tiny budget as a hobby. I will keep that mind to purchase years down the road when my A/C needs to be serviced tho, it's only a year old right now.

This is all on the 69 in my sig btw.

[H2Ogbodies]

I think you are on track with your temp choices of 205 and 220 using a 195F stat. For this use:

Wells #SW505 212/202 on/off low temp trigger
Wells #SW502 228/218 on/off high temp trigger

Of course any parts store can cross those to brands you prefer too-those temp switches are single male bullet style and you can use the GM knock sensor pigtails for them-cheap at a boneyard and easily found on late 80's-90's Gm pickups....located between starter and motor mount in passenger side of block. Hows that?

[anguilla1980]

Thanks for those temp suggestions, looks good.

I'm using my existing temp sensor tho so I don't need to buy anything fan switches/triggers.

[BonzoHansen]

Thanks for those temp suggestions, looks good.

I'm using my existing temp sensor tho so I don't need to buy anything fan switches/triggers.

What existing sensor?

[anguilla1980]

What existing sensor?

The Dakota Digital temp sensor that's in my water cross over.

[H2Ogbodies]

I guess Im confused-I thought you wanted low and high temp switch ideas-if you already have a DD switch then what temp on/off is it?

[dontlifttoshift]

He has a Dakota Digital sensor that runs the Dakota Digital PAC-2750 controller that is fully programmable for hi/lo on/off temperatures.

OP was just looking for suggestions at what temperatures those should come on and off at.

[anguilla1980]

He has a Dakota Digital sensor that runs the Dakota Digital PAC-2750 controller that is fully programmable for hi/lo on/off temperatures.

OP was just looking for suggestions at what temperatures those should come on and off at.

^This

Obviously based on the temp switches suggested that gives me an idea of what to program my controller for, so thanks everyone!

Alex

[CarlC]

Having the high-speed fan come on for AC may be a bit much. It's a lot of electrical load that will tax the system. Having the low-speed fan come on for AC may prove to be the ticket.

[anguilla1980]

Having the high-speed fan come on for AC may be a bit much. It's a lot of electrical load that will tax the system. Having the low-speed fan come on for AC may prove to be the ticket.

That's a good suggestion, because no matter what it's going to go into high if it reaches a set high temp anyway. I only mentioned that because that's how my factory cars have worked.

Thanks for the tip!

[H2Ogbodies]

Ah-ok. Well then I can see why the suggestion to use a trinary switch to activate high speed is ideal then. Inuse 3-speed conversion harnesses vs a controller so I opt to set mine up as low, medium and highspeed bypass using a trinary switch. But if the Dakota Digital is good for 250,000+ switching cycles then awesome! Underhood heat will kill it so hopefully its mounted inside somewhere.

[anguilla1980]

Thanks everyone for their help! I wanted to report back with what I set in my controller:

210/200 on/off low temp

220/210 on/off high temp

hi temp off mph - 52mph


How does that look to most of you? Again, 195f thermostat. I also have the A/C signal wire triggering the controller too.