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Old 07-16-2017, 12:59 AM   #1
Senior Member
Brand: Thor Motor Coach
Model: outlaw 37ls
State: Europe
Posts: 230
THOR #6831
a/c vents cold air repair

being a victim of no cold air in my coach. i added a can of freon and it did not work. after research it is shown that the control valve for the hot water to the heater core is the issue.

there is a control valve that is the main culprit, please refer to the link from:

this is a complete service manual from evan-tempcon, the supplier of most motorhome a/c units. the service manual indicates also the the water control valve is the issue before any other service is to be done to the a/c unit.

i purchsed a new control unit from ( comfort air in grand rapids michigan, they were helpful, friendly and had the parts in stock, it was $170 delivered, picture shown below,

it is super easy to install, the photo show it is above the battery and had 2 normal hose clamps used for installation ( credit to thor on this issue.

i did not drain the radiator the high location had very little loss of coolant, ( about 1 pint) took less the 20 min to install. getting the right screw driver took most of the time.

testing the result was more of a weird issue. to check the hose connections i had to turn on the heat for water to flow to both sides of the valve.

after getting normal engine temp. and plenty of hot air out of the dash vents, the a/c was turned on,

it took a long time to get cold air out of the dash vents

why? the heat setting had heated the the ventalation up to engine temp. it took about 15 min for the a/c unit to cool off the "ventilation core- box- air handling unit"

***if you do not wait long enough you can think the valve repair did not work****

then i had ice cold air and this was with the coach not moving just using the fan to draw air ( not best )

below are a bunch of photo's of the valve being taken apart for research.

there are 2 issues for failure of the valve, both are minor and could be serviced putting the valve back into use again

1st cause:

the large bull gear ( largest white gear) has a o-ring at the bottom between it and the actual control valve, this o-ring broke into 2 pieces jamming the gear. ( this gear will turn the valve). the o-ring is a dirt seal so i did not have any coolant leak.

2nd cause:

the valve was stuck, the valve is a simple ball valve design. debris from coolant had lodge into the valve causing a sticking condition. washing out the valve removed debris and allowed valve to move freely. i can assume that most coaches sit for long periods and many probably never get there heating systems really used,

the lack of use of the heating system means no water flow to clean out debris/sludge.

so a habit of turning on the heater for awhile will wash out the valve .

on the road service??

if your valve goes bad during a trip can it bee serviced on the side of the road?? yes, the circuit board / gear section could be removed and the valve turned manually.

with the broken o-ring i could not turn it with my fingers, the valve when removed from control section also could not be turned with my fingers, but after cleaning i could. small pliers was all i need to move a clogged valve

comments on photos

broken o-ring and large gear shown

control unit with circuit board/gears and valve separated

gear box and circuit board

valve location in engine compartment

the new valve

all the pieces ( yes it went back together)
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Old 07-16-2017, 01:26 AM   #2
Senior Member
Oneilkeys's Avatar
Brand: Still Looking
Model: Travato
State: Florida
Posts: 2,475
THOR #1765
Great post! Thanks for taking the time and effort to provide such a thorough explanation including excellent pictures, the manual and address of the company to purchase parts. I did not even know this part existed. Living in south Florida, I'm not sure I have turned on the heater in the year and a half I have owned the coach. I will gave to put that on my periodic checklist. Thanks again.
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Old 08-13-2017, 03:22 AM   #3
Senior Member
Brand: Thor Motor Coach
Model: outlaw 37ls
State: Europe
Posts: 230
THOR #6831

since the valve has been working, the ac from the dash vents is very good, a side problem now is that the dash heater/ac core can freeze up causing symptoms of a bad valve.

so now if i have warm or not so cold air, i turn off the ac for a bit so the ice can melt, you can also turn the temp control to hot to speed up the process but it will take bait cool off everything again.

how the duct work can flow air wit the core frozen ?? it will take some investigation
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