AC not cooling.

My AC struggles when it get's above 100 and my TT is only 25' long. Honestly I think you just don't have enough air for a trailer that big, it's going to take two units to do the job all the time.

ANY RV over 28 feet needs 2 Roof AC units. Your unit is to large for 1 AC. The largest roof AC is 15k. You either have a 13.5 or the 15k. If you have the 13.5 going to a 15k will not help at all. You need 2 roof AC units. Even if the existing one is working to spec, it will NOT cool your RV at all in temps higher than 80 degrees. Doug

Check out a couple of things.

Ex has the first thing to look at.

If it is not blowing air out that is 20 degrees cooler than the intake air is is not running sat peak efficiency. Some will not quite make 20.

Why add another one and keep the lame one setting in the hole also?

Get a 2nd A/C installed. Worth every penny. :) One was just not enough for our 32' 5th wheel.

Very possible that the evaporator coil is freezing over with frost/Ice which indicates dirty coils, air leak between intake and discharge sections, freeze sensor dislodged from evap coil.
When this coil freezes, air can not pass through it. Do you have better air flow just as you turn it on and then air flow decreases?

I added a single 5K window unit to the bedroom of my old 5th wheel. Used the top as a makeshift platform for a night stand (to one side of the bed) It's pretty easy to make good looking flashing to border the unit on the exterior. At night, it is magic, with the door closed. Ten plus degrees cooler than before. No need to keep the canned peas in the kitchen cool at 2 AM. During the day the bedroom door stayed open. No need to fool with mandatory 50 Amp shore power with this setup, either. I used a 10.6 EER 5K window unit with remote.

You could always try a portable one. They work pretty well.

Upgrading the existing one on the roof won't do anything you really need another unit.

Copy. Do you think i can buy one bigger unit or do u think i need two units

Depending on the outside temps, one A/C is going to struggle in a trailer that large (35 feet). Usually trailers that long have 2 A/Cs.