Why do both ac units ice up?

[dutchie01]

01 dsdp with 2 roof mounted ducted ac units, turned ac on about 4pm and by 1am both are frozen over and not cooling.
Anyone have experience with this?

[Shadowcatche]

There are a number of possible causes, low freon is one of them and restricted air supply/fan speed not high enough. The first thing to do is see if the indoor (evaporator-air handler) fan and compressor are both running at the same time, and at what speed the fan is running. Check to see there is sufficient air movement and that the evaporator coil is clean and not obstructed and the air filter is clean. That they are both both freezing argues for too low a fan speed or clogged filters restricting flow.

["007"]

What you may need is a good cleaning of your AC's.

[Senior Chief]

Our AC repairman just told us to keep fan speed high and turn temperature warmer (when we wanted less cooling) to control the icing on the front AC (which also suffered from low freon- recharged- nice and cold!)

[TXiceman]

90% of the problem with RV A/C is low or restricted air flow. On occasion, you will have one with a refrigerant leak.

With the age of your units, you need to check the evaporator coils, air filters and for air leakage between the inlet and outlet.

Leave the fan running on high, full time after cleaning.

Ken

[dutchie01]

The rear ac is new and the front is original. My set up has the little round filters in the ceiling seems if I remove them it does not freeze up, is it going to cause a issue running without the filters? Have even tried replacing them with new ones and it still freezes the front unit.

[TXiceman]

Without the filters you evaporator coil will load up with lint and cause more problems. Removing the filters helps to increase the air flow, so your problem is leading toward air flow problems.

Pull the interior unit covers and see if there are air leaks bypassing the unit internally. Get a roll of the aluminum tape from the hardware store and seal any seams. Checl where the duct connect to the ceiling and plug the leaks. Also plug the leaks around the wiring in the ceiling.

The last couple of units I put in had really poor sealing from the factory.

Ken

[George Z]

It would seem your problem is inadequate return air to the units. You might consider adding a few more return registers or use a coarser filter material to alloy more air to pass thru the units

["007"]

If your seals were not installed correctly you maybe drawing to much outside air and not directly out of your ducts.
Here is a Tech Bulletin as to proper installation.
Your bolts may have come loose and need to be tighten also.

["007"]

Here is another detailed cleaning process I had over looked.

[Don M.]

Dutchie....Had the same problems, same suggestions but nothing I did work. Took it to the dealer they said it worked fine but it kept freezing up (it didn't do it for them. Had to 3 different techs... finally they found it. It was some kind of sensor that had fallen off into the bottom of the unit and wouldn't sense the freeze-up. I'm no tech just telling you what they told me....But It works just fine now...

[footdoc]

I modified my wiring in both units so the fan will ONLY run on high instead of throttling back to low when getting close to the set point...

["007"]

This first link I gave you will tell you how to set AC to high speed just scroll down further and do follow the cautions described.

[wa8yxm]

I have heard of of seen A/C's ice up for the following reasons:

1: Dirt on the evaporator coils (mine did this)
2: Low coolant (Whatever they are using now days) Several commercial units I have "lived" with.
3: low air flow
4: Frost sensor (if so equipped) not properly positioned in the evaporator.

In my case, a good cleaning and making sure fan on high did the trick.

Very high humidity may do it too, if it's not warm enough, or so some suspect.

Recommendaton.. To "Defrost" run on fan only mode.. Do not shut off or niagra may fall when it melts.