97 F-150 Lariat 5.4, 4X4, auto.
I noticed last year on a long drive, the AC stopped putting out Cold air after a long time.
It's working fine for short periods. Good n' cool.

This year I noticed the same thing, and when I had the hood up, I see this white thing out under my hood that's all frosted.


What is that? What does it mean to me and my problem?

Is this a simple fix, as in more R-134 fluid?

 

The evaporator is freezing up.

Usually, this is caused by a cycling switch that is not opening when it's supposed to.

What you are seeing is the accumulator that is frosted. The switch screws into a port on the top of it. There is no need to worry about the charge when changing the switch as there is a valve under the switch that prevents leakage when the switch is unscrewed.

Replace the switch, available from almost any auto parts store. Just ask for the low pressure cycling switch.

Steve

 

Oh thanks for the good news. I was hoping it would be something simple I could do myself.

 

The problem can also be a slightly low freon charge. This is causing the evap coil to freeze up.

Another easy fix.

I dont think the low pressure switch goes out that often.

 

Hmmm, I should try to add some Freon first I guess. Since I dont even have the money for gas to get to the parts store, what would I do when I got there?
Thanks for the help.
We have a hot muggy summer going for us down here now. AC is as necessary as Food!

 

No. If you don't have gauges, you should replace the switch first!
If you blindly add refrigerant to the system you could damage the compressor. If it is fully charged and you add more to try it you will then be OVERCHARGED.

 

Change the LOW PRESSURE SWITCH.

IF the system was low and "freezing up" it would STILL be the low pressure switch NOT OPENING when the pressure got that low that it allowed it to freeze.