Hot air from vents when pulling trailer

[dbamber]

Hi folks
I have a 2000 7.3L and whenever I pull a trailer, the vents blow very warm to hot air, even though the temp control is set to cold. When I turn on the A/C, it does get cold, but I was wondering if anyone else has had this problem and had a fix for it. I just don't want to run the AC compressor when it really isn't needed.
Thanks for any thoughts you might have.
Dan.

[JSchuricht]

You need to install a valve to shut off the heater core.

[dbamber]

Thanks for your thoughts. Is that because the existing valve is leaking by or is this normal?

[JSchuricht]

It's normal. On most trucks the heater core dosn't have a valve and is always getting hot coolant pumped through it. When your towing, your creating even more heat than normal and it ends up coming out the vents. If you don't mind popping the hood when it gets hot/cold, just install a brass water shutoff on the line. Otherwise you need to make something work, either electric or vacuum. I have a vacuum one from a ranger that is controlled by the max ac position, but as I recently discovered, it dosn't help when towing through the desert and the ac goes out.

[aawlberninF350]

The heater valve is #74809 at Autozone. They probably cannot look up that number, but it fits a 98 Ford Ranger, plus many others. Splice the valve into the two heater hoses on the right side up near the cowl, then route about 5 ft of 3/16 vacuum line and T into the white vac line behind the glove box. When you select max ac the flow of hot water to the hvac is stopped so the ac is much colder. IIRC if you get the vac signal from the red vac line behind the glove box it will work on both ac settings, but then you will not be able to blend the temperature. I may have those colors reversed, been a while since I did it. There's a writeup around here somewhere. It's a great mod for scooting thru the desert in cool comfort!

[dbamber]

Thanks guys for responding. I am going to tackle this shortly.

[dbamber]

Another Question. When the cooling fan engages as we are pulling our 5th wheel, it sounds like the truck if going to launch as it is so noisy. Do you know if there are aftermarket electric fans available? Do you have any experience with these and do they work?

[JSchuricht]

Yes there are aftermarket electric fans. No they can't keep up when pulling a load. Stick with the mechanical.

[audioguru76]

i so need to do this on mine, but I always forget about it when I'm looking for a quickie project.

[dmd]

I just have a switch under the dash that I use to turn the valve open or closed. This
way in the spring and fall I can just use the vents and that air is cool. The MAX A/C
method only turns off the water when set at MAX, I can have it off and then
dont need to run max and the A/C is much cooler and quiet all the time.

Just get a electric over vacuum valve, you can get them from a place I think
is called Vintage Air.. Google them..