I have a 2003 Lariat Supercrew. I have been reading a bunch of places and I have a feeling that the problem now has to do with a vacuum line (which, I am cluesless), but I just wanted to make sure. Similar to other post, I also had a problem when I accelerated. The vent would swith to defrost. However, I had some mechanic fix that but there are other problems.

I also noticed that when I would be riding with the ac on, that air would be forcing its way in from the sliding rear window. It sounded like air was being pulled from the outside like a vacuum. I figured their is a problem either with the recirc or something.

I just replaced the compressor but it's still not cooling until I accelerate. It runs cold at night (still with the hissing sound from the sliding door) but I know something is wrong.

I live in Miami and the heat is just killing me! Any ideas?

Thanks in advanced!

Wayne

 

Barring other issues you might have with the control system, low speed cooling is very often low charge in the A/C system.
Big reason is at low speeds and at a stop, the condensor cannot cool and condense vapor back to fluid at the rate needed to provide re-vaporization again in the inside evaporator, the inside fan pushes air through.
I would also check the the fan clutch is not faulty or nearly free wheeling.
The condensor must rely on the fan to cool at low speeds and normal front airflow pressure at road speeds when the fan clutch disengages under heat from both the cooling system and the condensor, at road speeds
A shop needs to use a thermometer and check the air temp at the farthest outlet registers after the correct charge is determined and installed.
Then drive the truck and check the temps again for a drop and find out what is causing the control system to redirect or ?? airflow.
There is one other item that is seldom known; do not use straight water in the cooling system for A/C use. A really good operating A/C could actually freeze the water in the heater core that is right in line with the evaporator in the duct work.
Good luck.

 

Thanks for your reply. I was in the truck a lot this weekend. And it really has to do with low speeds. If I am reving at low RPM's it just doesn't cool. When I am bookin' down the highway, nice and cold. Then, I went fishing this weekend and having the trailer on confirmed that when the engine revs at a high RPM, it cools way better.



Again, thanks for all your help.