Evaporator fan sucking in rain

[wsmcycle]

I woke up in the rain storm last night to water dripping on my feet from the rear AC. I had replaced the base seal on the unit last fall. I thought it might need pulling down after settling. So I got a screw driver and a ratchet to get into it. When I got the face down I saw the water was coming in with the blowing air not the peripheral seal. I turned off the unit and the dripping ceased.
I reason that since the blower fan is a vacuum fan on the back side of the coil. There must be a seal that has failed on the evaporator box. I will have to go to the roof today and dig into it. Is there a commonly replaceable seal? I would like to go up there armed to repair. I hate that last step off the ladder onto the roof and that that fear is eclipsed by the first step onto the ladder from the roof.
Thanks

[Spk64]

Could be a clogged drain line.

[Solo_RV_Guy]

Originally Posted by Spk64

Could be a clogged drain line.

Helped a buddy with his "spitting" air conditioner and found the clogged drain. Compressed air and soft aluminum wire to "snake" the first couple of feet of the drain line and it was fixed.

[wsmcycle]

It is not a condensate problem. The drain line works all the time. I run this unit often. This problem happened while it was raining; no other time. I guess I will have to reconnoiter the evap box to see how it is sealed. I think i'll try and find a diagram of the the unit.
Thanks

[Old-Biscuit]

Not sure which A/C Unit you have????


Mine......fan room air shaft goes thru a seal on mounting plate which then is attached to evap coil housing
To access shaft seal you have to remove motor assembly with evap housing plate then squirrel cage air wheel then motor from housing plate


Could just be housing plate seal......any gasket material or goo can be used on it.
Motor shaft seal......might be able to find ????

[wsmcycle]

i went up top and took off the shroud. with the inside ON and water sprayed onto the roof under the pan, no leaks. when i sprayed water into the pan it began sucking in the water and spraying it out into the room.

it is a 9000 series coleman Mach unit from a 2005 country coach .
9023C876

a good diagram would help with search. i will google one if i can

thanks

[Old-Biscuit]

Exploded View
https://www.airxcel.com/DesktopModul...t/Pdf/r487.pdf


Technical Documents
https://www.airxcel.com/DesktopModul...t/Pdf/r487.pdf

[wsmcycle]

I bit the bullet and climbed on the roof to examine the rear AC. With DW inside,Ii sprayed water onto the unit. She exclaimed STOP! IT'S BLOWING IN. So I took off the AC shroud and removed the condenser fan so I could get into the evaporator fan box. The bottom tray of the box is molded Styrofoam (# 1) and it was in good shape. It is about 1.5 inch deep. Around the tray and extending from the base to the upper lip (#2) is a sheet of insulation.(# 3). the insulation was pushed down behind the wall of the tray. But in a few spots, the insulation (#6) was lying over the lip of the tray (# 4). The insulation was wet at these places from the test and water was dripping into the Styrofoam tray. The evaporator box operates in a vacuum created by the fan pulling air through the evaporator coil. This vacuum coupled with the miss-placed insulation had sucked water up the protruding insulation and into the Styrofoam tray. from there it was blown down into the bus.
I pushed the errant insulation back against the wall and behind the Styrofoam tray. And, to prevent this happening again I pushed a piece of thin plastic sheet (# 5) between the insulation and the tray from the base up to the lip (about 4 inches tall) all of the way around the tray. With that, I reassembled the unit and tested the "water invasion" again with a garden hose. No leaks, no water blowing into the bus. Good success.

KEY POINT Water was not leaking down into the box, it was being sucked up into the evaporator fan box from the base it was attached (but not sealed to). Any airflow restriction aka dirty filter, dirty coil creates greater vacuum in the evaporator box which increases the potential for leaking so I cleaned the coil and made a new filter.

[erkme73]

I know this is a year old thread, but I figure people like me will still find it years from now. I had the same issue with my 9024 series Coleman Mach unit, and unlike yours, my water ingress was from the fan motor shaft itself. Since the motor on these is vertical, and the motor is exposed to rain, any leak in the shaft seal at bottom of the motor will allow water in the motor to be sucked into the airbox. Note, this is a leak of the dynamic seal that prevents water from moving along the shaft itself - it is not the same as the gaskets and other seals at the motor base or mounting points.

I must had taken my AC apart and resealed it 5x before finally figuring out that it wasn't the condensate line, pump, fittings, gasket, etc.... The last time I opened the air box and found standing water in the styrofoam tray, I realized the water as getting in through the motor.

With the motor and airbox lid set aside, powered, and driving only the lower scroll fan, I slowly poured water on the top shaft. I watched as the motor wicked/sucked the water inside. Almost immediately, that same water came out below the lid, on top of the scroll fan. From there, it sprays out all over the airbox.

Since my coach has three identical units, I performed the same test on the second AC. No water came through the shaft below the lid. So I moved that motor/lid/fan assembly to the unit that we use all the time (bedroom).

I also reached out to Airxcel/Coleman (rvpsupport@airxcel.com), and that generously offered to send me the new seal at no cost for the motor seal (PN 8333-383). They said that seal can fail, and the replacement parts are available only through them directly, not distributors or resellers.

Again, apologies to the OP for being a thread necromancer, but I'm hoping this will help others who end up with a failed shaft seal like me...

[THenne1713]

Originally Posted by wsmcycle

It is not a condensate problem. The drain line works all the time. I run this unit often. This problem happened while it was raining; no other time. I guess I will have to reconnoiter the evap box to see how it is sealed. I think i'll try and find a diagram of the the unit.
Thanks

While your water issue maybe rain/ external drip down on fan, etc. SUSICION/ EXPERIENCE on (most/many) that throw water off the coil is that it is a (symptom of) a COIL that is DIRTY. E.g. As the coil gets dirty, it gets dirty FIRST in the center of the circle on an axial fan; i.e. coil surface for CFM decreases, AIRFLOW VELOCITY INCREASES across the fins of the coil (2-3x design) and water is no long able to DRAIN; due to the AIR VELOCITY (speed) it becomes AIRBORNE vs draining properly. HOPE this helps :-) PULL covers and inspect well while up there :-)

[erkme73]

Thanks to a PM from another user here, I was reminded to come back to post my final solution. As it turns out, the shaft seal on the blower motor had nothing to do with the water ingress...

It was the Styrofoam liner under the fan that had a barely-visible crack in it. As the interior blower fan runs, it creates a negative pressure dead center below the fan. Under normal conditions, this vacuum helps draw inside air through the evaporator. However, with a crack in the liner, it pulls in outside air into the plenum.

And since the only thing separating space between the bottom of the AC unit and the rooftop is that liner, if there is standing water in that space, that vacuum sucks the water up through the crack in the liner - and promptly dumps it into the supply ducting.

The fix is very straight forward... Remove the lid containing the blower motor to access the white Styrofoam liner, and then coat it with several coats of Drylok waterproofing paint (you can get it at Lowes/HD). It have virtually no smell, so it won't stink up the coach, and it completely eliminated the water ingress on all of my units. I can now run all units full blast in a torrent of rain without any concerns for water getting in.

Here are some pics showing the points of water coming in from underneath.

[THenne1713]

CLOGGED DRAIN a common problem on many auto air conditioners, (usually) related to (LACK of) a SCREEN at air intake at windshield base, putting leaves into the fan/ coil; later models also have potential for clogged CABIN FILTER, WHICH can cause HIGHER VELOCITY around the unclogged filter/ coil area, resulting in water not draining, but traveling into the airstream off of the coil.

[Old-Biscuit]

Originally Posted by THenne1713

CLOGGED DRAIN a common problem on many auto air conditioners, (usually) related to (LACK of) a SCREEN at air intake at windshield base, putting leaves into the fan/ coil; later models also have potential for clogged CABIN FILTER, WHICH can cause HIGHER VELOCITY around the unclogged filter/ coil area, resulting in water not draining, but traveling into the airstream off of the coil.

It was an RV Roof top A/C unit and OP posted resolution/fix on 4/24/21

Nothing to do with dash A/C

[THenne1713]

THX, missed that, but not sure how/why, as what I see NOW w/ pics is NOT what I was seeing that popped up ealrier on my screen