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Discussion Starter #1
My wife and I have a 2006 MDX. As of yesterday, the front ac has stopped working, only blowing hot air regardless of the temperature settings. The rear ac blows and works normally. The front AND rear ac both blew normally and cold just the night before so I'm not sure what happened.

Of course this happens 2 days before we have a road trip to visit family in NY and we'll be bringing rain with us so, no ac, no defrost. Foggy windows suck!

I looked through a bunch of threads and, originally, thought the issue could be the blower motor resistor. However, it seems, if the resistor was dead, there would be no air blowing at all (please correct me if I am wrong). My issue has to lie elsewhere.

You cannot hear the compressor engaging when trying to turn on the front ac but you do hear it engage and disengage when you turn on/off the rear ac.

I tried running the self test but couldn't get it to work. In order to do so, would it be keyswitch on while holding the AUTO-OFF buttons simultaneously or is it keyswitch on then hold the AUTO-OFF buttons.

Please advise so I can test this later and report back for further assistance.
 

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My 03-06 manual says to hold Auto and Recirc buttons w/ Key Off, and then start engine. Codes are displayed in the display.

You will need a shop manual to follow the rather complicated sequence and decode. Some have found the older manuals online.

good luck
 

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You're right - it's not the resistor (that only affects fan motor speed).

I wonder if it'll blow cold with the engine cold, first thing in the morning. If a heater blend door (the "flaps" inside the dash that route the air either through the heater core or the a/c evaporator) fails you can end up with full heat all the time, but it should blow cold until the engine warms up.

You can see if there's an error code stored in the system - turn the ignition switch to the II position (but don't start the engine), then press and hold the Auto button on the A/C control, and while holding it, press and hold the Off button. While you are holding these down, the temperature display should toggle between displaying "88" and an error code (if there IS an error code).

Or, it could be as "simple" as something clogging up the front evaporator core (which probably involves a whole lot of disassembly, parts buying and agony). Hope not...

Here is a chart showing how to interpret the error codes:


The manual I'm reading shows a different method than TexasHonda's - I'd say if one method doesn't work, try the other... ;-)
 

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The front air in my '06 gets stuck on hot all the time (seems to happen mostly when I roll the windows down; change in cabin temp confuses it?) and here's what I do to fix it: 1) dial CC all the way up to 'Hi', 2) let it blast heat for 5 seconds, 3) dial CC all the way down to 'Lo', 4) enjoy frosty AC (every now and again I need to repeat the process). I don't know if that will work for you, but it only takes 30 seconds to try and it's free, so what the hey.

I remember when I was researching the problem (search for "hot air in front, cold in back") that the usual suspect is a stuck blend door or possibly the air mix motor.
 

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Thanks for all the replies! We are heading out of town tomorrow but I have a few mechanically inclined friends who are going to take a look at the issue in my absence. I will let them know all the suggestions here and report back my findings for further assistance or a fix, which could benefit someone else.
 

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Hey everyone. So my friends weren't able to look at the car while I was away due to torrential rains.

I just tested for error codes. All I get is a toggle between 88 and _, so I assume no errors.

I tried pibcak's advice to no avail.

I did notice that, when the engine is cold (the car has sat, unstarted, for a week) cold air did blow out. Once the engine heated up, however, full on hot air.

What should I be checking next?
 

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Is the compressor running when hot air occurs? Is air heated or just not cooled?

If no, then first thing to check is whether the AC compressor is getting a 12V power at compressor connector to close the clutch and activate the compressor. If no, then either compressor relay fault or possibly other fault in AC controls; hi/lo pressure switch, evap thermostat, PCM.

If 12V power is available to the compressor, then either compressor clutch coil is open, or excess clutch gap.

good luck
 

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Discussion Starter #8
Is the compressor running when hot air occurs? Is air heated or just not cooled?

If no, then first thing to check is whether the AC compressor is getting a 12V power at compressor connector to close the clutch and activate the compressor. If no, then either compressor relay fault or possibly other fault in AC controls; hi/lo pressure switch, evap thermostat, PCM.

If 12V power is available to the compressor, then either compressor clutch coil is open, or excess clutch gap.

good luck
I will check this when I have a chance.

I also wanted to add that, even with the entire system off (heat, a/c) you can feel nothing but hot air entering the front vents when the car is running/driving. This is coming from the engine, no question. Straight, hot as can be, engine heat entering the cab.

Someone mentioned something about a flap not opening/closing properly. I'm starting to think this is the issue. Can someone elaborate on this?
 

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Discussion Starter #10
Thanks pibcak!

I pulled the air mix motor assembly and wanted to make sure I understand how it works:

The unit has an attached arm that raises and lowers the blend door depending on the heat or cool temperature selected, yes? So, in essence, when I press the red up temperature button or the blue down temperature button, the unit should rotate accordingly to raise/lower the door. This action shouldn't matter whether the car is actually running or just on (no engine on).

Is this assessment correct?

Also, is there an air mix motor fuse I can check? If so, where is it located?
 

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Re: fuses, check here for a nice little upload of the fuses and their locations: http://www.mdxers.org/forums/73-first-generation-mdx-2001-2006/37520-2002-mdx-center-console-power-out.html I would guess that fuse #3 in the driver's side panel might be it, since it's the fuse for the "climate control unit"? But it's also the fuse for a bunch of other stuff and if you blew it, you'd probably know.

Re: the operation of the air mix motor: I believe you are correct. Shouldn't need the engine running, just the ignition to ON. That arm coming out of the unit push/pulls the blend door and is attached to a gear inside the unit (that gear is often the problem when it breaks down and usually needs to be cleaned up and lubricated). You should be able to see it moving when you dial the temps up and down. That's my understanding, anyway.
 

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Discussion Starter #14
Well...thank you all for your assistance.

I followed every single guidline, suggestion and test outlined and, wouldn't you know, the damn air mix motor, which wasn't working at all, started working!

I reinstalled it and so far, so good. At least I know, if the issue occurs again, it's that part.

Thanks again for all the help. I must have magic hands or something lol.
 

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The problem w/ air mix motor is contaminated grease on the circular strip contacts (part of worn strip material causes grease to become conductive leading to shorts between strips). A large movement may temporarily remove offending grease blob allowing unit to function correctly. It may last a long time or a few days.

good luck
 
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