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Old 09-26-2021, 07:31 PM   #1
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Max A/C not as good as A/C - 2002 W22

I just drove my 2002 Itasca Suncruiser 35U (W22 chassis) and it seems like the Max A/C is less effective than the regular A/C setting. What should I look for and where? We haven't used it for over a year due to Covid so, other than periodic short drives it hasn't been driven.
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Old 09-27-2021, 12:36 PM   #2
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Winnebago installed the dash portion of your system , any indication of what manufacturer they used ; Evans or Denso are common suppliers .
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Old 09-27-2021, 01:50 PM   #3
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Go down where pass side foot well.. use magnet to find screws that hold kick plate to dash.. standing on head.. should be 2 wood screws... unplug rv.. if you have 110 outlet there.. mine does.. there you can pull blower and clean nest out.. start rv and see what is not moving.. there are all kinds of motors and cable driven doors.. look under dash at pass side.. while standing on head and you can see all the plastic shafts on top of HVAC box.. clean and lube.. lube cables.. lube door hinges.. use cell phone with camera and flash and record up under dash on HVAC box.. see if anything moving or broken.. put cell phone with camera and flash and record inside blower housing to far left and right.. record over far right over top of evap.. you are watching for critters, nest, shorts, or eaten wires.. ect.. pull out blower resistors pack.. clean and inspect

Your cell phone with camera and flash and record is your best friend and fits where your head cannot.. use it.. that should get you started
As always good luck and let us know what you did and maybe better members then me will help you
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Old 09-27-2021, 03:15 PM   #4
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Check to see if the air is going somewhere else...

I saw this on our 2009 W24 chassis. Max air didn't work as well as regular and sometimes all dash AC seemed to cut out, especially if accelerating (even a little).

The dash vent system is all run by vacuum. If there is too little vacuum, the vent settings don't hold. In my case, the cold air was being diverted to the defroster vents up near the windshield. While driving, have a helper check for this in your coach?

The vent system connects to a vacuum canister (looks like a baseball) on the firewall with the vacuum line running off to the engine. It is supposed to temporarily maintain vacuum for the vents when the engine isn't providing enough. That may not be happening. You may have a leak in the canister, the line or in the lines under the dash.

You might try installing a one-way check valve in the line coming from the engine to the canister. I did this, but haven't driven anywhere to see if it helped. I see those in the vent diagrams online for other GM vehicles (you can find the part on Amazon) but my chassis definitely didn't have one.

Worth checking for anyway.
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Old 09-27-2021, 05:41 PM   #5
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Max AC will still allow water flow thru the heater core - there is nothing to block it.

What Max AC does is recirculate only cabin air rather than pulling in some outside air and mixing with cabin air.

As mentioned above, making sure all internal dampers within the air box are working properly is key to identifying the problem, if there is a problem.

The one thing you didn’t mention is how long you let it run or drive the coach to make your determination. There is a lot of mass in an AC system and the cab of the coach itself - it can take 15-20 minutes of running, preferably at highway speeds, for things to normalize sufficiently to “feel” a difference.

You might also take the subjective assessment out of it by buying a good digital thermometer and sticking it in the closest vent to the air box. Go for a drive and monitor the two operating conditions.
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Old 09-27-2021, 11:33 PM   #6
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When that happened to my RV, it was a vacuum leak right at the switch. A hard area to get to (at least on my dash) but an easy fix.
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Old 09-28-2021, 08:44 AM   #7
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Thanks for the suggestions. I'll have to check things out.
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Old 09-28-2021, 09:14 AM   #8
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It should be noted that MAX AC only works better than normal AC once the ambient inside air temperature is cooler than the outside air temperature.
Use Normal AC to start, then switch to MAX for the best results.
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