Roof Air Blows Warm When Moving

[Ex-Tech]

Never saw this issue before.
My friend has a Duo Therm roof air on his ice cream truck. When parked, it works fine but when he drives, it starts blowing hot air within a few blocks.
Any ideas what would cause this?
I'm thinking he may have installed it improperly and outside hot air is being introduced into the cool air stream out of the evaporator coil.
He is in Lake Havasu at around 110 degrees outside.

[Sam_Spade]

Sam Spade wrote:
And what kind of POWER runs this unit ?
A generator that runs full time ??

Hello. Anybody in there ??

[dougrainer]

Ex-Tech wrote:
Hi, Chris! It has been a while.
The first thing I asked is if he installed it backwards and he did not.
Only thing I can guess is outside air is entering from somewhere.
The local shop tried to tell him that he had bought a park model roof air rather than a RV model and that park models aren't made to be run while moving and the problem is the vibration causes bubbles in the refrigerant oil.
I told him to run away from that shop.
Wish I was closer to help hm.

As with everything for unusual complaints---Your friend needs to
1. Post Model of unit
2. Can he post a pic of the install Upper and Lower?
3. Is it NEW or refurbished or used that he purchased.
4. HOW does he know he did not install it backwards? He may think he DID install it correctly.
5. Did he make SURE he installed the Plastic or Metal exhaust collar that directs COLD air from the upper unit to the interior plenum? Doug

[Ex-Tech]

Hi, Chris! It has been a while.
The first thing I asked is if he installed it backwards and he did not.
Only thing I can guess is outside air is entering from somewhere.
The local shop tried to tell him that he had bought a park model roof air rather than a RV model and that park models aren't made to be run while moving and the problem is the vibration causes bubbles in the refrigerant oil.
I told him to run away from that shop.
Wish I was closer to help hm.

[garyemunson]

RV Acs don't have any air path from outside to inside.The evaporator draws air from inside and blows it back inside, The outside just passes outside air through the condenser. Mr. Wizard is probably right. If the unit is installed backwards on the roof, as your friend drives, the forward motion of the truck is fighting the condenser fan and not enough air is passing through it. The AC cannot work if the condenser is overheating.

[Chris_Bryant]

Hey- it's been a while- good to "see" you. That's an odd one- note that Dometic changed the air flow with the BriskAir II- I don't remember which was which, but one sucks, the other blows 🙂 It would be good to see if the compressor is still running, and cycling off because it cannot dump the heat outside, or if outside hot air is being sucked in somewhere- or something else...

[Sam_Spade]

And what kind of POWER runs this unit ?
A generator that runs full time ??

[dougrainer]

He must have installed it backwards. Doug

[MrWizard]

could be, i think it will do that, IF he has it mount backwards
with the tail end coils facing the front of the truck,

noway the condenser fan can compete with external air pressure from a moving vehicle

remove (4) mounting bolts from inside
left up turn around
bolt back down