Hi guys i have a early 99 F-250 PSD a while ago my ac started acting up so i started playing with it. if i put it on AC or MAX AC and set it to all the way cold with the fan all the way on it is good and cold for about 10 to 15 min then goes warm..... or i should say hot. it is like i switched it to the heater. if i turn off everything for about 10 15 min then back on it starts to work again but then goes hot but does it faster then the first time. If i turn the fan down it takes longer for it to go hot. and i found that if i put the fan in the middle and turn up the heat selector *** about 1/4 off of full cold then when it does start to go hot it still feels some what cold and will stay there for a good long time.

My dad thinks that my evaporator is frezzing up but i'm not sure..

any help will be awesome. I have no idea where any switches and stuff like that are so any threads or pics will help me tons...

Thanks guys
Jeron

 

If the air goes to near ambient temp, the evaporator may very well be icing up.
If it seems to go to full hot, you have the dreaded Blend Door issue. It will be either a failed actuator or a broken blend door shaft.
Most of these require removal of the whole instrument panel to repair, but I'm not sure about the 99. I suspect so.

 

well sometimes it gets hotter than other times. and like i said if i turn the heat up a little bit it seems to stay cooler longer, thats why my dad thinks its the evaporator.

if i check one will the other be close by to check also or are they in completely different compartments. and if i am checking the evaporator will i still be able to drive my truck and stuff to see if it is icing. because another thing i forgot to mention is sometimes i let my truck idle for 10 to 15 mins. sometimes as long as 30 min, in the morning time while i eat my breakfast. if i forget to turn the ac off when i start the truck when i get in it it is like a ice box and the vents are pouring out ice cold air.

where is the evaporator and blend door located at and how is the best way to check if they are the problem.

Thanks

 

It really sounds like a blend door problem.
When it quits cooling, look at the 2 metal AC lines where they come from the firewall under the hood. They will be frozen over and the line back to the compressor will likely be iced over in the sections where it's metal.

If not, it's time to dig into the instrument panel. The actuator is behind the glove box and can be replaced without major disassembly (I'm told).
If the shaft on the blend door is broken, the entire instrument panel needs to be removed to replace it. Your best bet would be to find the factory shop manual.

 

ok i'm leaving in about 10 min so i will look at the lines before and after and tell you what i see.