AC Issue

[lmorgan]

My AC is blowing cold intermittenly. Checked the freon and it checks out full. The AC will blow fine most of the time, however, whenever I'm towing my horse trailer, it will sometimes stop blowing cold air. This seems to happen mostly when I'm in stop and go traffic or slow down considerably. I haven't noticed it when I'm not pulling a load so far. Sometimes when I accelerate, the air will start blowing cold again, but not always. I can sometimes turn it off and let it set for awhile and it will start blowing cold again. The pressure coming out of the vents is fine. The AC guy who checked my freon said the compressor was kicking in and out like it should.

Any clues?

[the trav]

sounds like it is condenser air-flow related...

condenser fins smooshed flat...
condenser full of bugs/dirt...
aftermarket partially-closed grille...
excessively worn fan clutch...

if the pressures check out fine when the a/c is blowing nice and cold... my money is on a air-flow related problem.

is is possible for the orifice tube to be partially/mostly clogged, but USUALLY if this is the case, it will never work properly.

-my .02

[jesilvas]

Sounds like the compressor. Get out and watch it one time. If it will kick on then cut off, sounds like the air gap needs to be adjusted.
Mine would do it. The clutches got so worn out that they wouldn't touch all the time and it would cut it off. Had it readjusted and it worked great.

[tracer7900]

2001 f350 7.3 a/c odor problem, condensation drain is draining any suggestions?

[lug]

Your odor could be coming from the under the hood to windshield panel. Lift it up and look for leaves, dead bugs, etc.

[ryno1121]

Put a thermometer in my vent. 58F while not moving and 72F at 70mph. The door that shuts the vent is closing and the compressor runs constantly while on max ac. Any ideas on what is causing this? Thanks

[lug]

Right around 77-78F outside air temperature and depending on humidty levels the compressor will stay on without cycling. You could check your freon pressure levels to make sure you have enough freon to ensure a proper vapor cycle or your blend door may be partially open. If it's your evap core orifice it can be water vapor icing up and causing a restriction, or worse your filter/dryer desicant material maybe circulating and causing the restriction. Since you said the compressor stays running you can put the cycling and cut-off switches on the back burner. I figure if your cooling system was jacked up you would have mentioned that so I would start with the easy stuff first. Try the blend door first.

[ryno1121]

Is the blend door on the passenger side behind the glove box? I can see the door open and shut as I turn the switch to AC or vent.

After I posted I went out and started the engine, let it reach operating temp. The vent temp was 59F, revved the motor to 2000 and temp went to 55F (truck not moving). Does this rule out any of the other causes you listed?

Seems like the problem is when the tuck is moving and not with engine rpm's. Makes me think it is the blend door also. Is there more than one door?

No issues with the cooling system.

Have not checked the freon pressure levels.

Thanks for the help. Trying to avoid the stealership!

[lug]

The blend door can be viewed at the floor board on the passenger side. There are two rectangles, shine a light in one and view through the other one. Turn the key to on, place the knob into the floor position. This will move the damper door out of the way so you can watch the blend door move. Move the hot/cold knob to each extreme position and view the door. The door should move smoothly. One position you can see it closed and the other the door disappears from view. If you have good hearing you can pick up the motor moving the door. The other door that is really easy to watch is the recirc door thats up under the glovebox. It will close when MAX AC is selected.