Author Topic: Dash heat/air  (Read 6689 times)

Adam Hicklin

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Dash heat/air
« on: July 02, 2015, 05:05:23 AM »
Second problem.  I can't get heat to stop coming through the dash vent, hence when I turn the dash air on, it's mixing with the heat.  I noticed this phenomenon this morning when I had the dash heat on.  Turning it colder as the temperature increased until finally the dial was on full cold but there was still a significant amount of heat coming through.  I know there is probably some type of mixing box controlled by the dash dial.  Anyone know how to access it and is it something I might be able to do on the road?  Temps are going to be in the triple digits tomorrow and I need some AC!

Bob Stone

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Re: Dash heat/air
« Reply #1 on: July 02, 2015, 06:48:08 AM »
Adam, I'm sure you are on the right track suspecting something amiss with a temperature mixing valve. However sometimes it is the very simple things that are overlooked. For some reason ACME (if that happens to be the heater, A/C in your rig) has  in some models reversed the temperature control knob. Where usually fully left or counterclockwise is cool or cold and right or clockwise is warm the opposite is true in some control units. As we would expect, blue is cold and warm is red.


Just a thought....

Bob Stone
'05 Monterey Laguna IV  Cat C-9

Joel Ashley

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Re: Dash heat/air
« Reply #2 on: July 02, 2015, 07:48:42 AM »
Even when it's working right, our dash air doesn't put out much cool air and never has, even when new.  Some have indicated that's the nature of the beast, and simply run the genset and forward house air while on the road.  Yeah, it uses more fuel, but can keep the interior tolerable when the mercury skyrockets, at least until you can check the control box gates.

Joel
« Last Edit: July 02, 2015, 07:52:07 AM by Joel Ashley »
Joel and Lee Rae Ashley
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David T. Richelderfer

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Re: Dash heat/air
« Reply #3 on: July 02, 2015, 02:10:27 PM »
When we first purchased the coach in August 2012 we were told the refrigerant level had been brought up to full.  At that time the coldness of the air coming from the vents was pretty chilly.  Now, three years later, that air ain't so chilly.  Two weeks ago I purchased the A/C Pro refilling system (20 oz. can and gauge attachment) at Autozone because it was on sale and my Avalanche needed a squirt.  I put over half the can in the Avalanche and nearly the remainder of the can into Leslie's van.  Now I need to find the fill port on the Marquis and get another can of stuff.  It's probably a fantasy anyway to expect the dash a/c to cool the coach much anyway... but in this heat having the dash air blowing directly on us sure helps.
« Last Edit: July 02, 2015, 02:13:21 PM by David T. Richelderfer »
2004 Beaver Marquis Sapphire

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Adam Hicklin

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Re: Dash heat/air
« Reply #4 on: July 02, 2015, 02:50:25 PM »
It's something about my return trip. AC was just serviced and was working fine on the way up. Granted it would never cool the coach but with it blowing right on youwhe driving, it did the trick. I'm sure it's a mixing problem. May have to follow Joel's advice and run the generator and house AC as a temporary fix. But I'd still like to fix the problem.

LaMonte Monnell

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Re: Dash heat/air
« Reply #5 on: July 02, 2015, 02:54:09 PM »
I have had issues with my dash air. First it was low on refrigerant, now after having the valve lash adjustment done and CAT looking over the coach I was told there is a compressor line leak at the compressor.

I haven't fixed it yet as it doesn't do that great when it did work, I just run the generator, the front roof air, and a big fan on the center console blowing air on me. Works better than the dash air so staying that way for now.
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Gerald Farris

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Re: Dash heat/air
« Reply #6 on: July 02, 2015, 03:53:18 PM »
Adam,
It sounds like you have a mix door adjustment problem. The dash A/C system has a door that controls if the air entering the coach comes through the heater core or the evaporator core. At max cool, all of the air should come through the evaporator core, and at max heat, all of the air should come through the heater core. At any level between, the air should be a mixture of the two. 

I have not worked on the dash A/C in a 98 Marquis, but it is probably just a cable adjustment at the dash control panel or the evaporator case. There could also be an issue with a heater control valve (assuming you have one) not closing when needed so the heater core is much hotter than needed and any leakage at the mix door causes hot air to enter the coach. You just need to spend a little time checking the system to determine the exact problem.

Gerald

Fred Brooks

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Re: Dash heat/air
« Reply #7 on: July 02, 2015, 05:19:02 PM »
     To prove Gerald's suggestion, here is an easy way to take the heater control  valve out of the equation. With everything running, block the wheels and crawl up under the front cap under the drivers windshield. You will find the evaporator attatched to the firewall. nearby you will find 3/4" heater hoses. Feel which of the hoses are warmer to the touch Take a needle nose vise grip plyers and pinch off the hose. If the a/c starts to cool, then you know you have hot coolant circulating into the evaporator which means there is an issue with the heater control valve. Check for proper operation. If the valve is "off" and have hot coolant hoses on both sides it is defective. Also make sure your condensor fan is running when the air is on.
          Hope this helps, Fred
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