Air flow in ducted roof AC systems

I found part of problem. Rear unit blower wheel was installed too far on the shaft placing the wheel about 1 1/2" from Styrofoam opening to evap coil. I moved it close to Styrofoam and air flow is much better. I think the ac should work okay now. Also blocked the duct forward of front unit as suggested.
Thanks to all, Jerry

Also there is a divider that separates the supply air from the return air in the bottom of the A/C unit. take down the ceiling cover and make sure the divider is there and sealed. Also seal to the cover when you put the cover back on. With out the divider the air just goes from the supply right into the return and not much to the ducts. I fixed mine and now and I can easily keep low 70 degrees when its in the 90's outside.

I had a 1998 Pace Arrow. I removed the front vent. The duct work continued past the vent over the tv. I cut a piece of styrofoam the size of the duct and placed it in the duct just in front of the vent. It helped increase the air flow. Not a whole lot, but it did help.

Thanks for the replies. I have checked for blockages and found none. No matter how the vents are regulated, the units will only push air to the rear of each unit. Virtually no air will flow forward. I am thinking of perhaps cavitation problem. Thanks again, Jerry

Don't expect too much. The roof units only move 350 CFM. Not a lot, just enough to get the cooling into the coach

Also pull of the bottom of each AC unit and make sure that they are sealed to the AC duct. If not taped properly, the air will leak into the roof structure rather than all of it flowing in to the duct work.

I experienced this problem as well. You need to get to the front vent duct at the front unit. I'll bet you find the insulating foam was not trimmed enough to allow good airflow. I trimmed mine and it did make some difference. However.!..!The airflow is still not as strong as the rear direction. It almost seems that the fan is managing to blow that direction. A small tower fan on the front console for additional air movement keeps us cool though; even in the hottest weather! I also agree that the proper air restriction with the vents is an added benefit.

Run both a/c units for max flow. If only one unit, close or almost close air vents where lots of air flow and leave the others open and it should improve. If it does not, I would look to see if something is blocking air flow or if something is misaligned. Good luck.

Mine has great air flow to rear bedroom and over kitchen. Adjusting vents and restricting where I do not need air as much has worked so far.

Is that with both running at the same time?