Hello,

I have a 2011 Crown Vic P71 Interceptor.

I had the A/C system worked on and recharged. When I start driving the a/c works fine and flows fine. After around 20-30 minutes the air will not blow as hard even on max and the only way to get air flow back is to put it on vent on max blower and eventually the air will come back and I can switch it to a/c again. What little air is coming out is cold there is just no pressure. I replaced the blower motor and blower motor resistor. Any help would be greatly appreciated.

I am in the same boat, though I'm not sure if it's the air blowing less or it's not as cold. Probably a little of both.

Ours takes a good hour or so for it to become "inadequate". My mechanic mentioned the low pressure switch at one point but he also said it was likely the compressor clutch getting weak, which can be replaced.

Al

When mine starts to weaken I can feel the cold through the vents but it's like the blender door started open then closed slowly over time. I know the HVAC controls work off of tubing so I wonder if it could be a leak.

I can feel cold also, but there's "cold" and then there's "COLD!". I think it's related to the compressor because even if the fan is blowing less on the higher settings, it should still be at least equivalent to the lowest setting on the fan, which is typically enough to maintain the temperature.

Al

Sounds like the evaporator is icing. You can counteract that by adjusting the cycling switch. Pull the plug and you'll see a small screw in there. Just a small tweak is all it needs. I think it's CW for less compressor time, but I could be wrong.

Cool Stu, I'll take a look when I get home, is that the switch on the compressor?

Not sure where it is on a late-model. Mine's on the low-pressure line (the larger one) near the drier.

It could be the icing i've heard where people need to switch to norm from max/recirc or it freezes and stops cooling. Can happen to home units too if the fins get clogged with debris. Do you have any sort of a mold smell from the vents by chance?

Mine doesn't matter if it's on max or normal, it doesn't cool enough when it's acting up. Doesn't smell like mold either.

But Rob did mention the compressor could be freezing.

Al

Uh, not the compressor, the evaporator.

Can you visually see the icing?

Al

Not without tearing the dash apart. The evaporator is the first thing they put on the car and everything else is built around it. You might see some frost on the low-pressure lines, though. That's not a sure-fire indicator, but it's a pretty good one. If the frost is heavy (more than just a skin) then icing is a good bet.

If you pull the blower motor you can see the evaporator.

Another symptom I forgot to mention: the defrost doesn't work in summer rainy conditions. It puts condensation on the outside of the window, which you have to keep the wipers on.

Normally turning up the temp to warm would eliminate that condensation, but it does nothing in this case.

Al