Community Forums

adoc1989 · 11-11-2012, 03:35 PM

I have a 1999 National Tropical 37 footer. Has anyone ever charged their roof AC unit, one of mine seems to be low on refergerant. What type of Refergerant does it have in it, R-134a, R-12, R-22 or something else? I'm not sure where you connection at is it inside or up on the roof?

clyon51 · 11-11-2012, 03:47 PM

My understanding is RV ACs are closed systems. In other words, you cannot re-charge them. I suppose a good HVAC person could put the hardware in place to do this, but that's just a guess.

TXiceman · 11-11-2012, 03:56 PM

Roof top units are sealed and require a lot of work to recharge properly. 9 times out of 10, the roof top unit does not need recharging. The most common problem with this type unit is the air flow caused by dirty filter, dirty evaporator coil or air leaks between the inlet and out let of the unit.

Lets start by running the unit on high fan and set the thermostat lower than normal. Let it run for 15 minutes. Now get an air temperature reading at the inlet to the unit and an air temperature as close to the unit as possible. The should be an 18 to 20 degF difference in temperature.

Check the unit amps when loaded and running as well.

Tha age roof top will be R-22.

Ken

adoc1989 · 11-11-2012, 05:54 PM

Thanks Ill try to check the air flow & filter, the other unit works fine

adoc1989 · 11-11-2012, 06:16 PM

Thanks TXiceman for your information. I have some automotive ac experence but nothing on RV units. I will look into the air flow problems and dirty evap or condensor.

smiller · 11-11-2012, 07:41 PM

As was mentioned your problem likely isn't low refrigerant, but if it is... attempts to recharge sealed units result in various levels of success and reliability. If you do end up diagnosing a problem with the refrigerant system or compressor then with 14 years on your current unit you may be dollars ahead in the long run to just replace it with a new model.

George Lewis · 11-11-2012, 08:08 PM

What the iceman says is correct...probably dirty, etc.... I had the same problem and the tech said "watch" and blew a pound of dirt, dust and assorted crap out of it and it works fine...do both ac while on the roof...

If cleaning does not work and there are internal problems, freon, etc...put in a new one...not that expensive as things go....you will have to down the road anyway...

Heating man · 11-11-2012, 08:36 PM

Quote:

Originally Posted by adoc1989

I have a 1999 National Tropical 37 footer. Has anyone ever charged their roof AC unit, one of mine seems to be low on refergerant. What type of Refergerant does it have in it, R-134a, R-12, R-22 or something else? I'm not sure where you connection at is it inside or up on the roof?

These units are sealed which means after they are charged at the factory the charging points are soldered shut and should not ever need refrigerant unless there is a leak. A leaking coil replacement on one of these units would be as expensive as replacing the unit.. unlike automotive units which have mechanical connections and rubber hoses. RV roof A/C units are all soldered copper which should not lose charge or need recharging.

adoc1989 · 11-12-2012, 01:41 PM

Thank you everybody I'll try to clean the units as soon as the weather permits and get back to you with the results.

TXiceman · 11-12-2012, 06:59 PM

As noted, it is not worth the expense of major repairs on a 14 year old unit.

I have worked with industrial refrigeration for 42 years plus and try to avoid A/C units. But I find I wind up helping on them in any case as there are a lot of A/C techs that are just parts changers.

Ken

whem2fish · 11-13-2012, 04:47 AM

I agree clean maybe you can this weekend if it doesn't work for a new unit I would call united Rv in ft worth good prices I think they are in haltom city on airport freeway at haltom road maybe 50 miles west of you join their membership save 10 percent that would pay the membership if you need help pm me I'm at 67 and 35 w maybe I can help. Dave

wickedrevs 56 · 11-14-2012, 04:24 PM

Iceland is correct, only time roof air actually needs freind is due to a leak. I use mag wheel cleaner from auto parts store to clean the condensed coils....be sure to rinse thoroughly. Amazing how much more efficient it makes the unit operate. Recommended once a year minimum, but we are un a coastal environment..