Ac isn’t cold at idle

[TheAutumnWind]

Its very hot and humid here. Same for where the OP lives. I used to have the same issue with my system. Yes it would work at idle, just not near as well. I tried a new fan clutch. That did a little, but very little. Then I tried a 12 blade fan with a new clutch, and that did a little better, but again, nothing like doing the electric fan swap. I did this on my truck, so this is first hand experience. It makes a world of difference, when your at idle for any amount of time in these hot, humid climates. There are a ton of videos on you tube with people saying the same thing I am saying. The large amount of air flow the electric fans pull across the condenser core, is so much more than any engine driven fan can pull, that it is a huge difference at idle. Again, I did this on my truck, and that is why I know what it does. My low and high pressures were with in spec, and my AC did the same thing as the OPs AC. As long as you were driving down the road, all was good, but once you stoped at the red light, the AC went from cold to cool. As soon as you stated moving again, the AC was cold again. Once I dis the electric fan swap, all if this went away. My AC is cold all of the time. Again, this is my experience on my own truck. Im Im not saying that the OP doesnt have other issues, maybe they do, and maybe they dont. And yes the system does need to be in good working order, and pressures with in spec, but an electric fan swap will make a big difference in the way the AC works at idle.

I don't deal with high humidity personally, so it is good to have your input on the matter.

Im sure the fans would help a ton at idle but it doesnt look like we have readings for pressure on the high and low side. That is still going to be my recommendation for first order of business.

 

[PlayingWithTBI]

Im sure the fans would help a ton at idle but it doesnt look like we have readings for pressure on the high and low side. That is still going to be my recommendation for first order of business.

That's why some manufacturers went to variable displacement pumps as well as electric fans on newer vehicles. When idling the compressor will go to a higher displacement so your pressures will stay about the same as when it's running at higher RPMs. The electric fans are the second half of the equation. I agree with @kennythewelder - at an idle, no clutch fan, or flex fan for that matter, will get enough air flow for proper heat exchange.

 

[kennythewelder]

I don't deal with high humidity personally, so it is good to have your input on the matter.

Im sure the fans would help a ton at idle but it doesnt look like we have readings for pressure on the high and low side. That is still going to be my recommendation for first order of business.

Oh, I agree 100 percent. The system needs to be in proper working order first and for most. I did a lot of research before I did my electric fan swap. I looked at flex-o-lite fans first, and that is a grate product, but the fans are nosey. Foe the average person that doesnt have the skill to build there own brackets and doesnt know how to wire up there own relays, flex-o-lite, is a grate choice. I know that electric fans off of some Fords do well on a swap also, like the windstar mini van. When I was looking for my fans, I saw a Cadillac DTS in the junk yard. Knowing that the DTS has a V-8 and that being a cadi, I knew the fans would be a good choice. Also size wise, the DTS radiator is about as wide as the radiator in my 97 Silverado. I also figured that the DTS fans would be quit. I was rite. They are very quit, and move a lot of air. We do a lot of aluminum and stainless work at the shop where I work, so it was very easy for me to make my own brackets. Ots been over 2 years since Ive done the swap, and I am very happy with the results. I never have an over heating issue, and my AC is always cold. It also get clod faster. There is always enough air flow across the condenser core to keep the truck cold. Oh and I have an extended cab, so there is more space to cool and keep cold than a single cab.

 

[Supercharged111]

Efan FTW. I had a good working fan assembly in my 1500 that sucked at an idle. Put in a MarkVIII fan and problem solved. The dually has a factory aux electric fan that seems to do well, it's colder at an idle than the 1500. I think its compressor is a lot stronger too though.

 

[BNielsen]

Efan FTW. I had a good working fan assembly in my 1500 that sucked at an idle. Put in a MarkVIII fan and problem solved. The dually has a factory aux electric fan that seems to do well, it's colder at an idle than the 1500. I think its compressor is a lot stronger too though.

How well do the electric fans keep your truck cool towing? I've been toying around a set of Flex-A-Lite fans when I upgrade radiators.
I know it's apples to oranges in a way, the 454s run a lot hotter than the 350s it seems.

 

[HotWheelsBurban]

Big block engines live up to their name. They take up a lot more of the engine compartment space than their small block counterparts. There's not a lot of space in a 400 series truck engine compartment to begin with, and when it's full of engine, it's harder for air to flow around and help cool things down. Even in a square body truck, the 454 (any big block) takes up a lot of space, way more than a 350. And the 400s aren't near as roomy under the hood as the square trucks were. Not trying to be pedantic, just stating my experience with the trucks my family has owned over the past 40 years....

 

[kennythewelder]

How well do the electric fans keep your truck cool towing? I've been toying around a set of Flex-A-Lite fans when I upgrade radiators.
I know it's apples to oranges in a way, the 454s run a lot hotter than the 350s it seems.

Electric fans do a lot better job of cooling than engine driven fans do. Electric fans, pull the same amount of air at idle as they do driving down the road, when they are on. The trick is to put the biggest set of dual fans that will fit your radiator. Also you need to look at how much CFMs the fans pull, and a set of fans will work better with a fan shroud. The more air your fans pull through the radiator, the better the radiator will cool.

 

[BNielsen]

Electric fans do a lot better job of cooling than engine driven fans do. Electric fans, pull the same amount of air at idle as they do driving down the road, when they are on. The trick is to put the biggest set of dual fans that will fit your radiator. Also you need to look at how much CFMs the fans pull, and a set of fans will work better with a fan shroud. The more air your fans pull through the radiator, the better the radiator will cool.

That's my plan, I'm looking at a dual 15" Flex-A-Lite E-fan rated for 5500-6000 CFM, and then possibly replacing the 9" pusher fan on the front with a 16" pusher rated for 3500 CFM, I'm hoping that will be enough to keep both the A/C ice cold and the truck cool.

 

[564crewdog]

FWIW...I had the same issue with a 90 Corvette, A/C worked great at speed and once stopped at a light the air became warm and muggy. It turned out to be a pressure switch inline with the A/C freon lines. Once I replaced it, the A/C worked like a champ. I'm not as familiar with the A/C routing on our GMTs but when I looked at my 97, there is an electrical switch behind the compressor on the left. The guru's in this forum will be able to weigh in on if this is a valid area to look at or not.

 

[Supercharged111]

How well do the electric fans keep your truck cool towing? I've been toying around a set of Flex-A-Lite fans when I upgrade radiators.
I know it's apples to oranges in a way, the 454s run a lot hotter than the 350s it seems.

My truck doesn't have any issues with heat when towing, and the fans are set to turn off above 35mph. Were the truck to get hot and need a fan while moving, engine driven is superior. I will not remove the engine driven fan from my dually, but I haul big and heavy with it. What radiator are you looking at for an upgrade? Stock 3500 or aftermarket?

Big block engines live up to their name. They take up a lot more of the engine compartment space than their small block counterparts. There's not a lot of space in a 400 series truck engine compartment to begin with, and when it's full of engine, it's harder for air to flow around and help cool things down. Even in a square body truck, the 454 (any big block) takes up a lot of space, way more than a 350. And the 400s aren't near as roomy under the hood as the square trucks were. Not trying to be pedantic, just stating my experience with the trucks my family has owned over the past 40 years....

Depending on what you're working on, the size isn't always an issue. The air doesn't cool the engine though, that's what the coolant is for. The dually will throw some serious heat though after a mundane drive. I'm amazed the stock cooling system works so well on it.