Roof A/C unit - blowing warm

[donschager]

Hello,

I have a Class A motorhome with 2 roof A/C units. The front one has started blowing warm air after only a few minutes use. Do these unit use freon like a front dash unit does, and if so, can they be 'recharged' by adding freon to them? If not, any ideas on why a unit would start blowing warm after a few minutes use? thanks!

[RVNewbie55]

I had one of mine do that a couple months ago. The shop I took it to said they don't try to repair them anymore as new ones are not that expensive relative to paying shop rates to diagnose and repair. My extended warranty paid for a new unit. IIRC the new 15K BTU with heat pump was around $1100, plus an hour or more time to R&R...Bob

[Old Scout]

The fact that the unit initially works upon start up but quickly fails after running for awhile suggest perhaps an electronic issue like a start capacitor or something. Older units use 134a while newer ones use 410 for coolant--most A/C shops wont mess with them for the reasons mentioned. You might find a tech who will "entertain" working on it but with a 10 year old system, you are already on "death watch" for something else to happen. Lot of good info on the forum regarding unit replacement and compatibility issues between a new one and your old unit--eg thermostats, mother-boards, and dip switch settings.......

[jcgribks]

Older units use 134a while newer ones use 410 for coolant

My 96 Itasca uses R12 in the roof a/c and R134a in the dash a/c.
I was told the same, they don't re-charge as there is no re-charge port on my Coleman roof units. But a previous owner added a clamp on port to my forward unit so I can re-charge mine. Got some R12 off e-bay. One unit takes 16oz of Freon.

[Sky_Boss]

You don't tell us what brand AC units you have so here is a possibility...

Our 2006 Newmar came with Dometic, Penguin AC/HP units. If you have similar AC units this may NOT be a refrigerant issue. This could be a problem with the reverser valve since it defaults to HEAT PUMP mode if it isn't activated properly. It is the reverser valve that puts your AC unit in HP or AC mode.

3 things can cause this:

1. Control board failure. - Replace Control Board.
2. Reverser Valve Solenoid Failure - Replace Solenoid.
3. Reverser Valve failure/stuck - Replace entire AC unit. There are no serviceable parts in the refrigerant system.

Newer Dometic units default to AC now.

Let us know what you have and I can provide you some more information on a couple issues if you have to replace a Dometic AC unit using a Duo-Therm 5 button CCC thermostat.

[TQ60]

Get the exact model number from the unit.

If dometic remove inside roof panel and look there.

Google that with manual and get a copy of the service manual then read the troubleshooting procedure 3 times so your brain is in gear.

Then proceed with the tasks in the list.

Could be a thermo protector on compressor or loose connection or bad board.

Many throw parts at the issue until fixed but that is waste of time and money.

[donschager]

thanks! Our RV is a 2013 Monaco Monarch, the AC is a Coleman Mach, model # 48004-969, and uses 410A refrigerant.

[brisath]

Originally Posted by donschager

thanks! Our RV is a 2013 Monaco Monarch, the AC is a Coleman Mach, model # 48004-969, and uses 410A refrigerant.

Any resolution to this? I have the exact same model number and it is not blowing cold air anymore.