Main A/C froze - Montana Owners Club

brenkco · 08-29-2009, 02:21 PM

We are at the state fair in Sacramento...around 100 today in our new 3455. We got back and our main a/c unit had frozen over. I ran the fan on the unit until the ice melted and then turned the temp back down. Fan was set to auto and thermo set to 72 on both systems.

The unit has cooled off considerably but still around 80 inside. I have a 2nd factory a/c unit in the bedroom.

I have a few questions.

Should I expect better cooling performance?

Any tips for running the a/c at night? The bedroom unit kept comming on/off at night. Even though we had the thermo set at 71, it was uncomfortable and never got to 71.

Do I have a defective main a/c unit causing it to freeze?

Thanks!

Ken

FLSTS03 · 08-29-2009, 04:50 PM

Ken, I'd PM OZZ on this one as A/C is his thing. Typicaly in a stick house dirty coils (indoor or outdoor) can cause freezing, dirty filters can also be a problem. I would also suspect that 100 outside temp and 80 indoor is not for from expected in a RV. Steve

Mrs. CountryGuy · 08-29-2009, 05:22 PM

Many times what is suggested is to run the unit on HIGH fan, if you have that choice. Surely not LOW fan. They tend to freeze up on LOW fan.

This is when day shades pulled, and vents covered/blocked (from the inside) can help. Try to keep the heat OUT.

But in those temps, as FLSTS03 states, a 20 degree differential is not so bad.

Run fans, like the ceiling fan, to help circulate the air, but I'll bet you know that one!

Enjoy that new unit!!

Ozz · 08-31-2009, 03:21 PM

Carol is a sharp gal!
Fan on high, 'on' setting, shouldn't freeze then. Problem with these units is that the ducting is rather small, not enough airflow. If it continues, use the 'dump' damper, ceiling fans on high.
Good luck
Ozz

brenkco · 08-31-2009, 06:35 PM

Thank you!
I'll give it a try.
Ken

Driftwoodgal · 08-31-2009, 06:55 PM

I just posted this on the thread titled "2nd AC" Sorry for those that have read it before.

We have a 2006 3400RL and live near Austin TX. We lived in our rig 9 months last year from July through April. Summer months were in Harlingen and Sept-April in Kemah. Have camped in 106 degree weather this summer too! When we first bought our Montana we only had one AC. Even with the silver sunshade panels on the windows we were unable to cool our RV so the second year we added the BR unit.

Just thought I would add a few comments about our bedroom AC. I love it as it drowns out all of the campground noise. I use it as a white noise machine and run it on fan mode during the winter. We can have a diesel truck start up in the early morning and not hear it. I love the fact that I can freeze during the summer by having it on high or just set it on low and close the bedroom door or leave it open to regulate the temperature. Closing the bedroom door allows you to really get it cold in the BR. We are like Glen and set the LR on a higher temperature.

The first thing I do once we plug in the 50 amp cord is to turn on our refrigerator and then I turn on the bedroom AC even before I put out the slides. This AC will start to quick cool our Montana. Our AC has to vents on it, one pointed towards the closet and the other toward the LR. I close the one closest to the closet and force all of the cold air down to the LR. The toilet area does get hotter with the door closed, so when it is real hot I open the door all of the way so air filters in there. We also keep the vent open in the LR almost all of the time. Hubby got tired of having to use an umbrella to open the vent so he put a file folder clip on it to hold it open.

Once we cool our rig down we are able to run one or the other unless it is over 100. The cooling down process can take 12 hours depending on when we setup.

One last thing, I have found that if you cover the vents to the basement with something you can keep the hot air from the basement from rising up into the rig. We don't keep anything down there that has to be cooled so the AC is better off keeping me cooler. I also keep the floor vents covered with a small mat so keep cat litter and debris from falling in there.

Colleen

PS Until we get our rig cooled off, that means internal temperatures of furniture wood etc our RV needs both ACs on almost all of the time. We have to put the LR unit down to about 68 or 70. When it is really hot I keep the windows covered with the silver sunshade stuff until the sun is not beating against the window, or I just leave the picture window uncovered.

sreigle · 09-04-2009, 01:00 PM

As far as performance, I would think it would take some time to cool down from that high temperature but with both A/C units running it eventually should do better than 80. Since we added the second A/C the highest outside temperature we've had is 96, with high humidity. The upstairs non-ducted unit was on high at the coldest thermostat setting. The ducted downstairs A/C thermostat was set at 73 and it was able to attain the 73 degrees and occasionally shut off the downstairs AC, but only for a short time before it started again.

snfexpress · 09-04-2009, 03:48 PM

Another thing you might look at is the freeze temperature probe that is stuck in the coils. When the coils start to freeze, the probe is supposed to kick the A/C into fan mode to thaw the ice (for want of a better explanation). Try moving the probe down to the first 5 inches or so of coils (the coils freeze from the bottom, up): this was our problem and when I moved the probe down, we no longer had any freezing because the A/C was doing what it was designed to do.

footloose · 09-12-2009, 11:32 AM

Quote:

quote:Originally posted by snfexpress

Another thing you might look at is the freeze temperature probe that is stuck in the coils. When the coils start to freeze, the probe is supposed to kick the A/C into fan mode to thaw the ice (for want of a better explanation). Try moving the probe down to the first 5 inches or so of coils (the coils freeze from the bottom, up): this was our problem and when I moved the probe down, we no longer had any freezing because the A/C was doing what it was designed to do.

Where do you find the probe? Do you have to take the cowl off of the roof or can you get to it from the inside?

snfexpress · 09-21-2009, 11:09 AM

To get to the probe, remove the interior white plastic cover. There are two screws under the plastic discs near the rear of the A/C and two that you will immediately see when you remove the filter grill. The two plastic discs can be removed with a thin screw driver or kitchen knife.

Once you have the cover off, you will see a white wire (if memory serves) going up towards the back of the A/C (back being closest to the rear window) and at the end will be a probe stuck into the coils.

If this isn't clear, let me know and I will try to clarify.

footloose · 09-21-2009, 01:22 PM

Thanks snfexpress. We haven't had a problem yet, but happy to have the info just in case.

You may also like: