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Roof air service


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Morning everyone, so i was scrolling thru my pics today and remembered i wanted to start a topic on what was supposed to be about of servicing the roof airs, however its now more about water leak prevention. 
So originally bought a cover for my front ac unit cause it wouldnt latch in place on one side.. which is now a different issue, however when i pulled the entire roof plate i saw the evaporator core looked dirty. So i used some shop air to blow out all the dirt witch made a dirty mess by the way, but the intresting part was when using the blower valve i bumped one of the bolts that holds the entire unit to the roof and it rattled! So i used my 1/4 in ratchet an was supprised to find 3 of the 4 bolts holding it on the roof were finger tight, not able to find a torque i just tightened them all even an “snug”. I pulled the rear unit cover an found the same thing, so i dont see ANY signs of water intrusion, however it would have been just a matter of time.

So with my roof faceplate there were only 6 screws holding it in place, however 2 of them were covered by the little covers that popped off with a little prying with a small blade screwdriver, then when reinstalling the faceplate it just takes a little effort to reindex the tabs back into place then put all the screws back in.

Tip: before using shop air turn on both roof Max air fans (cough, cough) and also have duct tape available cause there were  insulation flaps partially covering the passage ways heading to the roof ducts.

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yes, because of water intrusion and condensation, the bolts of the AC units frequently get loose due to the plywood they typically are screwed into gets soft.

You can inject some resin into the bolt holds, wait till dry, drill and rescrew with new galvanized hardware.  You can also redrill the bolt location near the original (so it hits the plywood plate in the ceiling).  And don't forget to silicone all holes when done.

Better than duct tape is actual HVAC metal foil tape for resecuring the internals.  Available at HomeDepot et al in the HVAC department.

I put a towel over the ducting entrances before cleaning the unit.  Compressed air is good.  I also use a pressure washer when I am impatient and cleaning rest of roof.  Must use with care.  And don't spray under the AC unit or the high pressure water can leak past the flimsy gasket material.

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Great timing on this post, especially with the warmer weather ahead.  I have a couple of questions, please?

What encompasses a proper roof air service?  Is it something I can do, or does it require the services of a shop?  I noticed our roof air (front and back) weren't really blowing all that cold this past weekend. 

Our roof air units are original to the Coach, complete with the persnickety 4 button DuoTherm tstat...would it be wise to budget in a replacement of both units with newer, more efficient units and tstat?  What would be considered a good replacement option?  And of course, is this something I could do on a weekend?  🤔😆

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About roof air service, when i owned my mobile rv bussiness i found that “some” savy techs can recharge some units, however i found that by the time some one relizeses the problem then the damage has already happened an theres no cost effective way to repair a old unit. What i have done in the past is to carefully remove the outer shroud covering the top of the unit, then carefully blow out the coils with air, then I use a water spray nozzel and spray from the inner side of the coils towards the roof, avoid flooding the inner workings of the unit. Leave the cover off in the sunlight a couple hours to fully dry. While thats happening go inside an remove the faceplate an use air pressure to blow out the dirt an such from what you can see on either side being carefull not to bend any fan blades or bend any fins( its pretty straightforward in that once in there you will see what NOT to do) Also i say this only for “what if” do all this with unit OFF an NO POWER GOING TO THE UNIT!!! Unplug your entire coach an turn off the generator. Then wash out or replace the filter inside an reassemble once its all dry.

As for replacing the unit, before concider doing it, realize how much that unit weighs, you will need to asses your own capabilitys, plus BEFORE you remove the old unit contact the manufacture an tell them what your taking out with the type of roof vent configuration you have so you will have all the pieces needed BEFORE you make a gapping hole in your roof an have to wait a week for parts to arrive from back east somewhere.

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Also I forgot to mention when checking A/C performance use a pin style thermometer an turn on your unit, a good performing unit should be able to achieve a difference of 20 to 25 degree difference between ambient temp to duct temp. When I take the temp I take it at the dump port on the faceplate of the air conditioner, using that you get a quicker response to the ability rather than waiting for the ducted roof outlets to cool down to be able to achieve the true output temps. When I am out in the Nevada desert where its dry and can get quite hot, I will start my units right around 7:30 am, that gives the units plenty of time to get the roof ducts cool so the coach stays nice inside.  My last trip there was 101 outside while the inside was 75 degrees, now this is with a coach that has 2 AC units and that was one of the things my new to me coach had to have. My 1st coach only had 1 air conditioner and I felt it was a total waste of money to run that on a hot day due to it couldn't keep up. On another note I do demand a lot from the air conditioners, however I demand more from my generator, having to output high amps for hours on end during the extreme heat, I always ensure I perform high maintenance before those trips. Then one other maintaince item I have incorporated into my routine is at the end of every season I now torque the connections at my transfer switch, common knowalge is high amp draw with loose electrical connections cause high heat, and on a older coach it is soooo important! It's funny I always envisioned having a motorhome meant being able to enjoy more time relaxing and taking in the sights, which is true however im finding the trade off is the more you use it the more your maintaince schedule needs to encompass more things, more often. Stay cool and enjoy the good times!!!

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