I have a 1986 RV with the orginal Rooftop AC made

Question edited for clarity.

Check out the link for fan motors.

https://www.google.com/search?q=Coleman+TSR+replacement+fan

..

low ac and low air only

yes

Controls at wall thermostat, or manual at ceiling?

COLEMAN R.V. AIR CONDITIONER SERVICE AND REPAIR QUESTIONS
COLEMAN R.V. PRODUCTS
GO TO rvcomfort.com
Click on RVP (RV PRODUCTS)
Click on type of AC, if you can’t find the information you want there,
then click on contact us on the Green Bar.
You can get Service Support or Email address and Phone numbers.

COLEMAN R.V. PRODUCTS
GO TO rvcomfort.com
Click on RVP (RV PRODUCTS)
Click on type of AC, if you can’t find the information you want there,
then click on contact us on the Green Bar.
You can get Service Support or Email address and Phone numbers.

Is this a new unit/RV by any chance?

It probably has a clogged condensate drain. Take off the cover on top the RV and check hoses or tubes leaving unit for debris or lint. Often this water is used to help cool the condenser so look for leaves pine needles etc in the pan. There may be a cover you can remove on the evaporator section that will allow you to clean the collection pan and hose or trough. Is it possible the RV is far enough out of level that the condensate can't "run uphill"? Always power off while working on this unit unless you are electric savvy. Good luck!

COLEMAN R.V. AIR CONDITIONER SERVICE AND REPAIR QUESTIONS
COLEMAN R.V. PRODUCTS
GO TO rvcomfort.com
Click on RVP (RV PRODUCTS)
Click on type of AC, if you can’t find the information you want there,
then click on contact us on the Green Bar.
You can get Service Support or Email address and Phone numbers.