Air conditioner prob?

[paineszj]

1999 PSD when im driving with the air on high it looses power after about 20 min of usage and feels like it is on low? The first time it did it I was towing in the mountains and I thought that the truck was turning it down itself to prevent over heating or engine damage from running hard. It did it to me this weekend again without a trailer just the truck. No rise in engine temp, no loss of power. I cant figure it out?? it blows really cold, but with very little power? Any Ideas?

[mschn99]

just out of curiosity, feel up and see if the cold air is coming out of the defrosters instead of the vents, i wonder if your electric vacume pump might not be getting weak and the air is getting diverted to the wrong place becuase of it...

[paineszj]

I will give it a try tonight after work, I will let you know what happens tomorrow thanks alot!

[paineszj]

Gave it a try! It doesnt blow out the defrost, just gets really weak as if someone turned it on low! But it does it after about 30 min of running everytime?

[fordman1]

It almost sounds like the evaporator is freezing up.You may need a new cycling switch .

[mschn99]

does it pick back up if you take it off A/C and just run it on the vents?? is it the A/C or the blower motor for the fan is what im getting at???

[paineszj]

Im thinking its the fan! If I shut the air off for 10 min after it craps out it blows hard again.

[overl0rd]

Maybe the resistor is bad and getting hot.

[fordman1]

it will blow normally again after the frost melts off of the evap .Put in a new clutch cycling switch .