AC question

[Gregorio]

My AC blows arctic cold. Problem is, it never stops! After a couple of hours on the road it gradually freezes till no air is coming out but the fan is still running. I turn it off for a while and when I turn it back on small pieces of ice and very cold water blow out the vents.

Any ideas?

[Snakeyes_Tx]

Yeah.. I'm jealous!

Uhh.. just dont turn the thermostat to full cold? So it turns the compressor on and off.

Notice how there is no "In between" temperature... actually.. maybe your 86 does. I think mine did.

My 83 Has COLD and OFF. The thermostat switch just makes it blow full cold on and off and the "in between" is the compressor not shooting the juice through the system and you get that watery smelling air.

[Gregorio]

I think I understand you, Snake. You said set the temp slide somewhere to the warm side of cold, right?

I'll try that after while and see what happens.

[Bob Barry]

And I thought "it blows ice-cubes" was just a figure of speech!

;)

As Snakeyes noted, the temperature lever on your dash not only affects the heater, but the A/C output as well. Or it should. There is a sender that touches the coils inside the air-box, and if it's not working, the unit won't know when to cycle off and on.

Try the dash lever first, though, and see if that helps.

[Lindel]

Greg, when it freezes, is there actually ice on the hoses, and evaperator coil? If so, then you're under charged on freon, be it R12, or R134a. It sounds to me like you need to add a little freon to your system.

[64Trvlr]

I think the reason your a/c is freezing is the humid air where you live. When you have humid air and the a/c turned down as low as it will go the moisture in the air freezes on the condenser and eventually builds up to the point where no air will flow through. If you have a recirculate position use it if not, try to leave the temp control in a slightly warmer position. I think that will do the trick for you. :cool:

[Gregorio]

I tried sliding the temp control to a warmer position. In fact, I slid it all the way to Hot! and turned the fan to low and all points in between. The thing still froze me out this morning.

Plan 2, anyone?

[Ralph]

Most likely, you've got debris in the evaporator housing and/or the fins of the evaporator itself that will need to be cleaned out.

What happens is that moisture is drawn to the cold surfaces of the evaporator. It's supposed to drain neatly away and out through the tube. But when you have debris and even fungus in the evaporator housing, these things absorb and hold moisture, which in turn freezes to ice and thus causes drain blockage.

The fix is as follows:

(1) Lower the evaporator and blower housing;

(2) Carefully unpeel all the insulative tape (it's gooey and don't throw it away);

(3) Clean out the debris out with a vacuum attachment, and use a cleaner to get the gunk out of the fins;

(4)Carefully rewrap the insulative tape -- I just did this a week ago and basically went nuts with duct tape;

(5) Bolt it all back up.

Total time is about two hours.

You don't need to discharge the refrigerant. But I know the job was easier for me because my system was completely empty of refrigerant: I could unbolt the evaporator hose (larger hose) from the compressor, giving me more room to pull the evaporator housing from under the dash to work on it.

[Gregorio]

Thanks, Ralph.

[Michael F]

Lindel, Ralp, You all are correct on that when the pressure in the evaporator drops down to a point that it can freeze water it may be low on charge or have debris that are restricting air flow.

The FSJ a/c system runs close to freezing (40deg discharge at max) with pressures below freezing (average 20psig with R12) to be able to overcome the extreme temp load of a FSJ interior that has been locked up in the sun.

What keeps the system from turning into an ice ball is the temperature control stat that should be on the evaporator or real close to monitor the discharge temp.

Gregorio stated that the system would run real cold and after a couple hours he would get no air at all after it had froze. So it sounds like it has good air flow at the start and the compressor never turns off even with the temp contol set warmer. If the compressor does not turn off then the most likely problem is the temp control as Snakeyes sugested or the temp sensor is not seeing the correct temp and turning off the compressor in time.

[Lindel]

The thermo couple was going to be my next suggestion, since it sounds like it might not allow the compressor to cycle, but in the Texas heat, there's a good chance the compressor won't cycle on and off. Mine doesn't, when I've got the temp control set to max. But mine doesn't ice over, either. Checking the evap core for debrise blocking it is a good idea, as well as checking the condensor coil for blockage. But check the freon level, too.