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"MAX" Button

G

GregAbell

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Location
Itasca, IL
The "MAX" button is for the recurculation valve motor. Where is this motor located? The service manual just says its on the HVAC ducting, but doesn't call it out in the diagram. The truck was sitting for a while (as I'm sure others have been with fuel prices), and now when you start the truck and after you shut it off, I get a knocking sound from the duct. I've timed the knocking sound and its 21 seconds - the manual states that the recurculation valve motor doesn't have a potentiometer feed-back, so it runs for 21 seconds. The rod has probably disconnected from this motor, so I need to know where its at to either fix it or just disconnect the motor. Is it possibly between the duct and the firewall (I pulled the glove box and couldn't locate it, but the sound seems to be coming from the back-side behind where the blower resistors are located)?
 
You are technically correct in posting this in Interior Components, but I am going to move this thread over to the 6.5 forum for better exposure as it relates to your '94.

Bud
 
This button will engage a flap in the heaterbox. If engaged, the flap will open and the heating system will suck the air from inside the cab. If closed, it sucks the air from the outside. Also known as SMOG button. Run the blower, press the button and have a look up to the heaterbox from the passenger feet aera and watchout for a flap moving. Try to engage and disangage, so the flap will open and close. Normally, you should be able to push it open by hand. Be careful that you don't damage something.


Hope this helps.

Cu,
Sven
 
I know that's what it does - where is this motor physically located on the HVAC ducting?

The Service Manuals (Helm Inc) call it out and describe it's function, so I'm confidant this is what is now causing the noise, but for the "diagram" the manual just states "not shown"
 
I just finished reinstalling my evaporator case/airconditioning unit. I had pulled it out of the truck to replace the evaporator core and the heater core. Tons of fun. OK, here's how to find your recirc door actuator:

Look under the dash on the pax side. Find the a/c blower fan. Put your hand on the lower left side of the curved blower housing. Now push your hand forward, towards the firewall insulating pad. The LAST thing you feel before your fingers touch the insulation pad will be the actuator motor. You'll be able to feel it operate as you cycle the MAX button. HTH!
 
Good chance the gears are worn or the troll beating the plastic plate with a wooden spoon is angry.

My answer was to fire up the truck, place the system is recirculate, and then pull the connector from the stepper motor so it stays in recirculate. Occasionally, my system freezes up so I turn the air off until the volume of air picks up then its back to ac. No big deal; you won't miss it.

BudTX, I complement your thoughtful moderating. Thank you.
 
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In my old truck, I did the same thing Dan is suggesting. Worked just fine, until winter rolled around... as soon as the recirc started picking up the humid air (humidity caused by the snow melting off my boots), it circulated that moist air up onto my windshield (the outside of which was, like -30*C) and PRESTO!... I had an instand skating rink on the inside of my windshield! Fogged the damn thing right up!

Solution #2: I got a vent control off an old farmer's field car and used it to open and close that recirc door. Also gave me the ability to partially close it...


And I agree with Dan... good job, Bud!
 
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