I have a 99 f350 and my a/c does not work at idle at highway rpm it blows cold. but once i let it sit and idle even on 1300rpm high idle it will now blow cold. it blows hot untill i rev it up aroung 2000rpm or drive down the road. I have charged the a/c system it has the proper about of refidgerant in it compressor gap is correct. Is it supposed to be like this? If not what are some things to check? Thanks Justin

 

OBS truck I had showed similar problem. Replaced the condensor up front and that cured it. Seems over time sediment fills up the lower part (like a radiator) which causes it to be ineffecient.

 

Is the fan turning fast enough at idle?

 

Check the front of the AC compressor to see if the clutch is staying engaged at idle. If it doesn't, tap on the clutch and see if it starts working.

My AC stopped working a couple of years ago at idle, but worked fine when driving. My issue was a worn AC clutch. Autozoo fixed me right up with a replacement clutch.

New pulley and clutch on left, old, grooved pulley and clutch on right.



No more problems since June 2010

 

What's it take to put a new comp clutch on. I have basic tools I'm visiting family in Missouri I mean is it somethin I can do real quick?

 

If the clutch is clicking, but not locking up, you may be able to take out some shims.
This may help.

https://www.ford-trucks.com/forums/5...ml#post4464164

 

X2...My A/C did the same thing, and removing a shim cured it.

 

Just going off memory, you need a small ratchet to pull the little bolt out of the center and a pair of snap ring pliers to remove the snap ring. That and a breaker bar or 1/2" drive ratchet to get the serpentine belt off.

I tried to adjust the air gap on mine. My problem was the face had deep grooves worn in it.

 

My bet would be on the fan clutch . If the ac seems to work on the high way and when you rev it up the fan isn't pulling enough air through the condenser at idle. How hard is it to turn the fan by hand ? When you first start your truck and take off in it and I mean drive it right after start up do you hear the fan for a minute or two till the truck warms up? You should be able to feel air blowing decently from the fan after warm up. It's also possible the radiator,cac or condenser could be plugged up with bugs or dirt not letting air flow just use some compressed air to blow it out . I'm not sure about the comp clutch though I think it wouldn't work at all if it was worn maybe some others can chime in.

 

Yep same thing happened to me, fan clutch no good!

 

More good info

 

well i redid my a/c system new compressor, orifice tube, drier, blew out evaporator and condenser. and i do not think it blows as cool as it should i have used many thermometers and driving down the road 110 degrees out and a/c on high it blows about 45 degrees out the vents. sitting still on high idle 1300 rpm it blows about 55 degrees. does this sound right?

 

check for vacuum leak and blend door under dash

 

If checking for a vacuum leak is not detected. crimp off the heater hose and see if the a/c temp drops. Also what were the pressure readings for the high and low sides at idle and 1300 rpm's.

 

I know you said you changed the compressor. Did the new compressor come with a new clutch assembly? The clutch air gap should measure between 0.014 inches to 0.030 inches. Most people just say a minimum of 0.020 because it is in the middle of the range. To verify this gap, ensure your engine is NOT RUNNING. Turn the key to on but not started and turn the AC controls on like you want to run the ac. The compressor clutch should energize and now you can measure your gap without incident. Don't leave it enengized forever...ok. It will drain your batteries over time as it takes some power to pull that coil armature in.

The heater core always has hot water running thru it. Take a cloth or rag and wrap it around one of the hoses going to your heater core to protect it and then use a pair of long bill or duck bill vice grips to gently clamp it shut. Only use just the amount of force necessary to clamp and hold the vice grips in place. Does this help with the temps at idle??

You can remove your blower fan and use a garden hose to rinse out your evaporator core inside your truck. You want High pressure and low/slow volume from the hose so that the drain line can accomodate the drain rate that your hose is producing. In other words, don't put too much water in too quickly or you will have a leak inside your cabin floorboard area. When you initially start this spraying of water for like 10 or 15 seconds....ensure to look under your truck to make sure the water is actually draining.

You can purchase a ford ranger 4 way valve and some vaccum hose and make the water shut off to your heater core automatically when you go to MAX AC but that is another thread entirely. This is why you are clamping off the hose to see if this improves the efficiency to see if you want to do this mod to your truck.

Ok. You have plenty to do now to make it better. Make it happen.
Dwayne