I just bought a 1999 F-150 yesterday and when i was driving it today the A/C turned hot when i accelerated. If i turn it off and then turn it right back on it does the same thing again when i accelerate.

I believe it is my vacuum hose but i dont know where that is on the truck any help or suggestions on what else it might be. If someone could show me a picture of where the hose is would be great too thanks for the help

 

The A/C compressor is disabled under WOT. Under an extended WOT run on a hot day this is normal. If the A/C gets hot under part throttle acceleration you have other problems.

 

Well if i am idleing or maintaining a constant speed i am usually ok it is when i am accelerating normally i hear a faint click "i think" coming from the engine area and it starts to blow hot air even if i stop it does not return to cold it stays hot i have to turn the a/c off and wait a second and then turn it back on and it will blow ice cold until i accelerate.

 

If I remember correctly, a vacuum leak will cause this. When you accelerate, you no longer have enough vacuum to keep the blend door in the right position.

 

The click is the compessor clutch dropping out.
I bet the system needs a charge.
The pressure switch on the dryer controls the compressor clutch.

 

Busted blend door.

If the clutch were dropping out, the problem would be loss of cooling, not getting HOT.

Vacuum has nothing to do with the temp control.

 

Could also be the clutch wear. If you take off the 8mm bolt on the front of the clutch there might be shims (washers) under the clutch face. If so try removing one and see if that helps. This changes the gap in the clutch. Had it happen to my 97 150 and it has been working great now for two years.
You don't even have to take off the belt.
Here is a picture of the breakdown.....

Ron

 

lots of vehicles shut off the A/C compressor during acceleration; automotive engineers figure you might need the extra power to pass or in an acceleration emergency, like getting around that truck before the next bridge.

 

Guys, he said the air was getting HOT, not that the A/C stopped cooling....

That's a difference of several dozen degrees.

If his description is accurate, the blend door is BUSTED. Seen it too many times.

If the clutch were dropping out due to either air gap problems or the WOT was cutting it out, the outlet air would go to outside ambient or so, not HOT.

Have to look at the indicated symptoms. Now, if he exaggerated the description of the symptom, then the clutch would most likely be the problem.

Steve

 

Could be an accumulator comin apart too. We see this in the super duties(infact i just did one yesterday). where the orifice tube gets clogged and the high goes very high and the low side fluctuates fast as the compressor draws a vacuum on the system. you need an ac gauge though.....usually under highway conditions this happens.

 

Ive seen this before on a few F150s.

On a really hot day,AC works fine when cruising,but when you step on it.A/C cuts out and air is no longer cold or even warm.Instead you get hot air(Arizona)
3 out of 4 times,it was a coil pack causing a slight misfire under load and PCM disabling A/C compressor.
When you cruise again,A/C is restored.

So my suggestion is,power brake your truck and if you feel even a slight misfire.Then you have found your problem,now all you gotta do is find out which coil pack is misfiring and replace it or the defective boot.