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harleyman134 · 04-10-2012, 06:11 PM

My evaporator coil is freezing up, so it looks like I need a new a/c unless somebody has a better idea. I have a heat pump right now that I never use so I'm considering an a/c unit only, will this be a problem. Also I need some tips on installing it in a 2005 MADP 4304.

targaboat · 04-10-2012, 06:31 PM

You do not need a new AC for it IS getting cold. My guess is that one of the sensors is not function. Replace that and truck on. It you are considering installing a new one than it appears to me that you can figure out what to replace.

Or you do not have enough air flow for some reason.

oh no · 04-10-2012, 06:49 PM

check the filter it needs air flow. Or it will freeze up,

harleyman134 · 04-10-2012, 06:52 PM

Quote:

Originally Posted by targaboat

You do not need a new AC for it IS getting cold. My guess is that one of the sensors is not function. Replace that and truck on. It you are considering installing a new one than it appears to me that you can figure out what to replace.

Or you do not have enough air flow for some reason.

It cycles off before reaching target temp. The compressor cuts off and fan switches to high for about 3 minutes before cutting off. I went out this morning and pulled the temp sensor out of the coil and it ran a good hour then the flow from vents slowed down and I went up and the coil was frozen over. I believe I have good airflow, all intake filters are clean and I have a good seal on the unit. I'm guessing low freon.

TXiceman · 04-10-2012, 08:16 PM

First thing to check is the air flow....yeah, I know you THINK you have good flow. 95% of the cooling problems with RV A/C units related to air flow.

Clean the filters, check the evaporator coil and make sure there is not build up. Next, check the baffle between the inlet and outlet side of the fan. Any leakage can cause it to freeze-up the evaporator.

On the remote possibility of a refrigerant leak, look the unit over for any oil spots on the tubing and fittings. If there is oil, you have a leak.

Cleaning the evaporator may mean pulling the unit from the roof, removing the top sheet metal to the evaporator and using a foaming coil cleaner and a water hose.

The units are hermetic and the only way to get a leak is a hole in a line, so that is WAYYYYYY down the list of problems, but it does happen.

PandK · 04-10-2012, 08:28 PM

What you are describing is exactly what I saw last year on mine. Low freon was the cause. Started to ice up at the bottom first then the ice would work its way up the coil. I replaced the A/C unit in about 30 min after the dealer put the new unit on the roof for me. Easy job.

Romeo · 04-10-2012, 09:53 PM

Quote:

Originally Posted by targaboat

It (if) you are considering installing a new one than it appears to me that you can figure out what to replace.

???????

ottffss · 04-10-2012, 10:54 PM

Quote:

Originally Posted by harleyman134

...Also I need some tips on installing it...

Newmar's HVAC guy, Norbert, has a couple of install tricks I like. It's a 2-man job getting the unit up/off the roof. One guy carries the unit on the ladder on his back the other guy removes it.

1) When installing the roof units use silicone caulk spread all over the aluminum tape used to seal along the duct edges and seams - use lots of silicone spread around with your fingers. This is to keep the aluminized tape edges from tearing. Newmar now also uses a pretty high quality and thick aluminized tape (I don't know the brand) as the cheaper stuff tended to shred/peel and then vibrate in the duct airflow.

2) The bolt support blocks, typically the white styrofoam-like junk, instead buy a second square main gasket (usually grey in color and much denser) and cut these 2in bolt squares from that material. They also stick to the bottom of the AC when installing making that easier. Compress to about 50%.

I'll add to make sure and set the DIP switches on the new unit to match you original unit DIP settings.

"007" · 04-12-2012, 03:55 PM

If you have not seen it you need to install the AC seals correctly for the Newmar ceiling vents.

harleyman134 · 04-12-2012, 05:38 PM

007, thanks for the link, that's the kind of info I'm looking for

harleyman134 · 04-29-2012, 10:19 AM

UPDATE Before I did anything else I decided to check the seals on the roof as suggest by you people. Problem No. 1 the metal tape used to seal the ducts off from the roof were torn and needed to be replaced. Problem No. 2 the Newmar Service Bulletin link provided by 007 shows a gasket to seperate the cold air from the return air which was not in place on this unit and I could definately see how this could have an impact on my air flow. I got some gasket material and make a gasket to seperate the air and this should solve my problem. I feel good about this. I ran it for about an hour with the generator without any problems, I look forward to my next trip so I can give it a good workout.

Thanks for all the help

PS. The a/c I was having a problem with looks like it had been replaced before I bought it (plastic evaporator coil cover vs a metal one on my rear a/c) I can only surmise that when this was replace the repair tech did not know to put a gasket here.