A few years ago I bought a used Carriage 30RLS with ducted AC. This has always been stored inside a storage building. This building has 2owners who I will call A and B. The door is just barely high enough to get my unit into. The door stop springs have to be compressed to get the fiver inside. Last fall when I was putting the unit away the wife of owner B was the person who opened the building for me. I specifically asked if the door was open all the way and was told yes it was. As I was backing up, the door seal contacted the AC was tapped. I stopped right away and checked. The AC unit was knocked slightly out of position. The AC was twisted slightly, by about an inch. How much damage have I done? Will this cause leaks next summer when using. What about when I am driving down the road in a rain? The roof does have a slight crown so water should run off, if no wind, but I am concerned about wind driven rain.

If it was knocked out of position as you say, I'd get it looked at just to be safe.

At the least it'll need to be removed and the new seal installed under it.

The next time you are going in or out, make a visual inspection of the door before moving your unit to assure that the door really is where you need it to be. As the driver, YOU are responsible for making the clearance.

Probably no damage. But the 14 inch square hole the AC covers does not have a tolerance for a AC out of square. So, on your unit you just loosen the 4 mount bolts and then align the roof AC and then retighten the bolts. Doug

If the AC unit has been moved, something structural was damaged.I lived on a street with a big oak tree overhanging the street. I drove my unit under that tree a hundred times and never had an issue. One day the limb contacted my AC unit. I had the same issue. There was barely any noticeable damage. I took it to the dealer to be checked out and they found that the joists in the ceiling had been broken. The total cost was 3500. I paid the 500 dollar deductible and the insurance covered the rest.

AC knocked while crossing door? | Good Sam Community

30 Replies

dougrainer
Nomad
Feb 13, 2015
Cloud Dancer wrote:
Thanks for the information on different A/C mounting methods. This kinda explains why I was only able to tighten the bolts on both of mine a whole 1/4 turn. Now I'm curious to know if lag bolts means there's some kind of wood structure up there. All I can see inside the ceiling is aluminum super structure. It looks like all this framework is fabricated in-house,.....mig welded.
My guess is that if I ever drive under a low bridge and hook a A/C unit it'll probably total my motorhome. Scary

The Newmar Lag bolts hit Aluminum. That it is IMPORTANT to never apply too much torque to those lag bolts. You can easily strip out the aluminum and then have to go to a large diameter lag bolt. Doug
Cloud_Dancer
Explorer II
Feb 12, 2015
Thanks for the information on different A/C mounting methods. This kinda explains why I was only able to tighten the bolts on both of mine a whole 1/4 turn. Now I'm curious to know if lag bolts means there's some kind of wood structure up there. All I can see inside the ceiling is aluminum super structure. It looks like all this framework is fabricated in-house,.....mig welded.
My guess is that if I ever drive under a low bridge and hook a A/C unit it'll probably total my motorhome. Scary
Dutch_12078
Explorer III
Feb 12, 2015
As Doug said, it doesn't take a lot to move the typical RV roof A/C that's been in place for awhile. Other than the Newmar type, they're not actually bolted to the roof, but rather clamped in place with the roof sandwiched between the inside and outside sections.
dougrainer
Nomad
Feb 12, 2015
Cloud Dancer wrote:
All these posts have made me very curious. All of these A/C units are bolted on with 4 substantial bolts (at least all the ones I know). Therefore, I have to wonder what kind of weak attachment could there be that whenever the A/C is impacted in the way this one was, that there would not be damage to whatever member receives the bolts? Did the bolts break and cause the unit to move? Did the bolts pull out? What?

The AC gaskets compress over time. That means, if you hit the roof top unit just a little, it can move. I have repositioned scores of roof AC's that have had this type damage done. Now, if you have a Newmar type unit that is bolted (Lag screwed) from the top down, then all bets are off. To move a top bolted down AC will mean there IS damage. Doug
trailerbikecamp
Explorer
Feb 12, 2015
Cloud Dancer wrote:
All these posts have made me very curious. All of these A/C units are bolted on with 4 substantial bolts (at least all the ones I know). Therefore, I have to wonder what kind of weak attachment could there be that whenever the A/C is impacted in the way this one was, that there would not be damage to whatever member receives the bolts? Did the bolts break and cause the unit to move? Did the bolts pull out? What?

OP here. This is why I asked the original question. When I got up on the roof to check, the AC had only been shifted/twisted out of position by about an inch. There was no visible damage to the AC. When I moved the AC back, it moved pretty easily. Because it moved fairly easy I am not sure if there is any damage. It was only the weather stripping/seal that contacted my AC.

I have never had to take the AC off any trailer before so I don't know what to expect when I do this, or the best way to do it.
Cloud_Dancer
Explorer II
Feb 12, 2015
All these posts have made me very curious. All of these A/C units are bolted on with 4 substantial bolts (at least all the ones I know). Therefore, I have to wonder what kind of weak attachment could there be that whenever the A/C is impacted in the way this one was, that there would not be damage to whatever member receives the bolts? Did the bolts break and cause the unit to move? Did the bolts pull out? What?
Huntindog
Explorer
Feb 12, 2015
dougrainer wrote:
Huntindog wrote:
TucsonJim wrote:
I'd loosen the mounting bolts, reposition, then put a sprinkler on the roof for a while to check for leaks. If you don't have any leaks and the unit is functioning okay, you're good to go.
NO!!! Water can cause damage. Whether from rain, or a sprinkler.

I would pull the unit, inspect the area for damage, fix as needed and install a NEW gasket.

If you want to check for leaks, have the unit pressure tested.

This is good. NEVER use a rain booth or sprinkler to check for leaks. Use a "pressure test". Yea, right. water only causes damage if not caught in a timely fashion. Most AC's can be slightly moved like what the OP had happen as long as they are bolted from the inside. The "tell" if the roof is probably damaged is the damage on the roof top unit. If it is creased or smashed in the odds are the roof material may be damaged. You can take the AC loose and lift up and easily inspect for damage. Then align and re bolt down. Unless the gasket is old and extremely compressed, there is no need to replace it. Doug
Well I gotta disagree. Using water to "check for leaks is ALWAYS a bad idea. One never knows just where the leak is, and where it will show up. Sometimes it can enter at one place on the roof, and run over to a wall and down the inside of it. You may not even see it if you are looking where you think it should be. So you could proclaim it good, only to have wall damage later on down the road... And that is just one example of what can go wrong.

TO the OP... Though it is unlikely that you have serious damage, the consequences of being wrong are severe... I would remove the AC, and give it a really good inspection. LOOK, LISTEN, and FEEL the rafters etc, while someone else walks around on the roof. This will give you the best chance of discovering hidden damage such as a cracked rafter that will get worse when the unit is bouncing down the road.

A fix NOW if needed will be MANY times cheaper than a fix later.

Good luck, and let us know the outcome.
mabynack
Explorer II
Feb 12, 2015
jmckelvy wrote:
mabynack wrote:
If the AC unit has been moved, something structural was damaged.......

Not necessarily. On our Alaska trip last year my brother went under a really low bridge and knocked his AC completely off the top of his trailer. No damage other than to the AC unit and wiring harness. Didn't even tear the rubber roof. RV repair guy couldn't believe it.

I suspect this is not the usual case though.

It's possible that I'm just jinxed. I blew a tire on my FW several years ago and it didn't look like there was any major damage. I took it to the dealer to get the fender replaced and they found 1600 dollars worth of damage. He showed me pictures and gave me a detailed breakdown of the damage so I know he wasn't lying.

The same with hitting the tree limb. I didn't see any damage when I looked at it from both above and below, but the dealer said that the ceiling framing had been broken. That was several thousand.
j-d
Explorer II
Feb 12, 2015
trailerbikecamper wrote:
The door is manual chain operated. To compress the springs, I have to pull a little harder on the chain that operates the door. Then there is a notched holder that one of the chain links slides into.

My idea of a "prop" of some kind was to be able to know you had clearance if it was in place. With this chain-pull door, how about this:

Pull till you know it's clear, then mark the link that has to be pulled down to the top of that chain stop. The one above the one that bears on the slot from the bottom. Use paint, tape, the like. And, not that you won't after this experience, look for that link every time.
dougrainer
Nomad
Feb 12, 2015
Huntindog wrote:
TucsonJim wrote:
I'd loosen the mounting bolts, reposition, then put a sprinkler on the roof for a while to check for leaks. If you don't have any leaks and the unit is functioning okay, you're good to go.
NO!!! Water can cause damage. Whether from rain, or a sprinkler.

I would pull the unit, inspect the area for damage, fix as needed and install a NEW gasket.

If you want to check for leaks, have the unit pressure tested.

This is good. NEVER use a rain booth or sprinkler to check for leaks. Use a "pressure test". Yea, right. water only causes damage if not caught in a timely fashion. Most AC's can be slightly moved like what the OP had happen as long as they are bolted from the inside. The "tell" if the roof is probably damaged is the damage on the roof top unit. If it is creased or smashed in the odds are the roof material may be damaged. You can take the AC loose and lift up and easily inspect for damage. Then align and re bolt down. Unless the gasket is old and extremely compressed, there is no need to replace it. Doug

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AC knocked while crossing door?

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