Are three bolts enough?

[Newback]

So I accidentally cross threader one of the 4 lag bolts holding on my Coleman Mach 5 roof top AC, the other three are snugged tight and are fine. Is it safe to tow for a trip I have planned in two days?

[chuckster57]

You’ll be okay, but you’ll want to fix the problem asap. Those 4 corner bolts pull down the foam seal to keep water out. If one is loose, or missing that’s a possible leak.

[Newback]

I may have to drill a new hole, the original hole has the cross threaded bolt sheared off in it.

[chuckster57]

The AC will have “nutserts”, you may be able replace it.

[notanlines]

OK, I'll ask, how does one 'cross-thread' a lag bolt?

[Newback]

Thanks for the tip! From looking at the parts drawing, it appears that I may be able to get at the nutsert from the roof once the plastic shroud has been removed.

[chuckster57]

Originally Posted by Newback

Thanks for the tip! From looking at the parts drawing, it appears that I may be able to get at the nutsert from the roof once the plastic shroud has been removed.

You will have to remove the other 3 screws, and lift the AC off, then turn it up on its side.

[linux3]

The way everything in the RV industry is built "Just good enough" and sometimes not even that good I would really worry about having only 3/4 of the design spec.

[Newback]

Originally Posted by notanlines

OK, I'll ask, how does one 'cross-thread' a lag bolt?

I installed an RV Airflow system and thought I had the bolt lined up correctly and tightened it with my drill, before I realized it the bolt was cross threaded and it snapped.

[Newback]

Originally Posted by chuckster57

You will have to remove the other 3 screws, and lift the AC off, then turn it up on its side.

Do you think the nutsert will be “removable” from the underside of the AC basepan?

[NH_Bulldog]

Our last camper had one cross-threaded mounting bolt from the factory. We discovered it when we opened up after the first winter and the ceiling was water damaged. Jayco denied the warranty claim, saying that we never had it in for any of the half dozen “required” service checks in the first year. I filed a complaint with with our State AG Consumer Protection Dept and after what seemed like forever, we got it settled.

One little 20¢ bolt that failed to adequately compress the roof seal caused over $1,800 in damage.

[chuckster57]

Originally Posted by Newback

Do you think the nutsert will be “removable” from the underside of the AC basepan?

You will have better access to it.

[flybouy]

"One little 20¢ bolt that failed to adequately compress the roof seal caused over $1,800 in damage."
Newback you came to the right place and it's good you asked. The bolded quote above is so true. An inexpensive, seemingly "minor" part or event can cause damage. Sometimes catastrophic and deadly. Never assume "it's no big deal" or "it won't matter" especially if you don’t have a deep knowledge or an understanding of how it works. In this instance the mfg designed the unit with 4 points for sealing/securing the a/c unit. There isn't a redundancy built in and shouldn't be because when the 4 screws are secured properly as designed it works.

Let everyone know how your repair progresses and keep asking the questions.

[Newback]

Thanks for all the inputs and ideas. It does sound like that the three bolts I have remaining will get me through the trip I have planned in a few days, and I'll be able to fix this properly when I return home in a couple of weeks.

Thanks All!

[Newback]

Originally Posted by flybouy

"One little 20¢ bolt that failed to adequately compress the roof seal caused over $1,800 in damage."
Newback you came to the right place and it's good you asked. The bolded quote above is so true. An inexpensive, seemingly "minor" part or event can cause damage. Sometimes catastrophic and deadly. Never assume "it's no big deal" or "it won't matter" especially if you don’t have a deep knowledge or an understanding of how it works. In this instance the mfg designed the unit with 4 points for sealing/securing the a/c unit. There isn't a redundancy built in and shouldn't be because when the 4 screws are secured properly as designed it works.

Let everyone know how your repair progresses and keep asking the questions.

Will do, I'll post the solution and take some pictures.

[Hballer21]

You can drill the center of the sheared bolt and back it out. You can get a removal kit at the auto parts store (how do I know). Or, just drill it with a reverse twist drill bit which will remove it.

Buy a threading tool and rethread the hole (possibly with the same size if it wasn’t too boogered up, and replace the bolt. If not, you might have to go larger.

[chuckster57]

Originally Posted by Hballer21

You can drill the center of the sheared bolt and back it out. You can get a removal kit at the auto parts store (how do I know). Or, just drill it with a reverse twist drill bit which will remove it.

Buy a threading tool and rethread the hole (possibly with the same size if it wasn’t too boogered up, and replace the bolt. If not, you might have to go larger.

That usually works on a bolt that’s broken off in a solid surface. A nursert is a threaded rivet, and the shaft of the AC bolt is about 1/4” if that. If you try to drill or use an ez out you’ll most likely twist the nutsert out. BTDT.

[Todd727]

Originally Posted by Newback

I installed an RV Airflow system and thought I had the bolt lined up correctly and tightened it with my drill, before I realized it the bolt was cross threaded and it snapped.

I think his point is that what you are talking about isn't a lag screw (often mislabeled as a bolt because of the hex head), but a machine thread that threads into a nut. Lag screws thread into wood or concrete and do not use a nut.