Adding Second A/C

tech740 · 05-10-2018, 12:05 PM

I have the opportunity to get an A/C unit to add to my 5th wheel. It is already wired for 50 amps and has the wiring next to the vent as a prep package. I understand that I remove the roof vent and the A/C unit goes through that hole. My question is what do I put between the A/C and the roof to seal it. I have never had a vent off the coach and would like to do this only once if I make the decision to add it. Thanks for any and all help.

**JRTJH** · 05-10-2018, 12:16 PM

A NEW air conditioner will come with a foam rubber gasket that sits between the roof and the "top unit". That foam rubber gasket seals the roof to prevent any water intrusion. If the air conditioner is USED, then you should purchase a new foam rubber gasket to preclude any potential for leaks from the old gasket not conforming to the roof and not sealing properly. Depending on your trailer, you may (or may not) have thermostat wires, access to the ducting and electrical power at the roof vent. So, you may find it much easier to use a "inside cover" that has thermostat and fan switches rather than attempting to connect the unit to existing ductwork and the trailer thermostat system.

Installation is "straight forward" once you get the upper unit positioned on the roof. The hardest part is lifting that 75 pound, very awkward component up a ladder and across the roof without damaging the side of the trailer, the roof membrane or your back..... Be careful and think it through BEFORE you get half way up the ladder with it on your shoulder..... BTDT

**chuckster57** · 05-10-2018, 12:23 PM

The other part is cleaning off the sealant from the membrane. I’ve seen people just plop the AC unit right on top of it, makes it near impossible if you have to replace the AC unit.

tech740 · 05-10-2018, 01:18 PM

Thanks for the replies! Sorry I see now that I did not post all the information. The unit is used. It is a unit that has the knobs attached. It is currently on my parents motor home that they no longer use and plan to sell to a demolition derby. The A/C worked great just other parts were wearing out and they wanted a toy hauler 5th wheel. I will have to stop and get a new foam rubber seal. I am hoping to do this at the end of the month because the motor home is parked next to my 5th wheel. Make it easier to hand it from one roof to the other. There is no R/V dealer within about 45 minutes of where the units are so I would like to make sure I have all that I need when I go up there.

**JRTJH** · 05-10-2018, 01:48 PM

If the A/C is used and currently installed on an RV, I'd urge you to plug in the RV, turn on the A/C and see if it even works, blows cold air and doesn't have noise issues. Those things are not "repairable" and call for replacement. In other words, I'd suggest you not install it on your RV, find out it's low on Freon and doesn't cool. The "fix" for that is to replace the top unit. Might as well not waste the time and effort of getting a $25 gasket, installing the A/C to find out it's junk. On the other hand, if it works on the motorhome, chances are it'll still work after making the 10' journey to your rooftop. You can buy the gaskets at any RV store, Amazon and EBay or at any internet RV parts site.

tech740 · 05-20-2018, 06:15 PM

So I have the new seal and plan to do this over the weekend. I have tested the A/C and electric heater that is built in. I think the only question I have left is how tight do the 4 main bolts need to be? Are they torqued?
Thanks for all the help.

**chuckster57** · 05-20-2018, 06:21 PM

We try to get the gasket cinched to about 1/2 it’s orignal thickness. Don’t try to do it in one step, work your way around and slowly pull the gasket down.

tech740 · 05-20-2018, 06:25 PM

Quote:

Originally Posted by chuckster57

We try to get the gasket cinched to about 1/2 it’s orignal thickness. Don’t try to do it in one step, work your way around and slowly pull the gasket down.

Thanks, That is what I will do then.

tech740 · 05-29-2018, 06:33 PM

So as a follow up, this project went well. A little wire had to be added to get it routed to the preexisting wiring in the ceiling. Only issue I ran into is that the 96 motor home that we took it off of had a roof that was thinner. Had to get some threaded rod to get it bolted down to at least be weather tight. Other issue is that the cold air discharge doesn't meat up with the mounting plate anymore. Found a Duo-Therm duct extension online and have that ordered to fix the issue. That comes with longer bolts also it seems. So all in all I still only have 40 bucks into a second A/C and seems like it should work great. Thanks again for all the help.

**chuckster57** · 05-29-2018, 06:38 PM

Your way ahead of the game! Good going .

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