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Recirculate door malfunction Help!!


M.Richter

Question

I am at a loss I have a 2001 GMC Yukon XL slt with dual heat and AC, I will try to explain this as simple as possible, since I purchased it about a year ago the Fresh/Recirculate Door stays in the Fresh position! I have replaced the Recirculate Actuator the one close to the passenger defrost vent, It has power because when I push on the door through the glove box it fights back! The switches on the heat AC control module work (so it seems) the light switches between the 2 modes as I would expect but the door will not change position! I know there are modes that recirculate is not available! I can get the recirculate light to stay on but the door does not move! Now to explain everything I have done to hopefully fix this and other issues, ( replace orifice tube, Receiver/Drier, Recirc Actuator, vacuum down system, add 5oz of Pag oil plus 5 more (the amount recovered from Drier) added 3 lbs of R134a (what the system called for) I pulled the schematics from a Mitchell manual for the AC wiring but can't make heads or tails of why it has 2 high pressure cutout switches? I did check a repair chart that mentioned one of the high pressure switches causing the recirculate door to malfunction? But causing it to stay in recirculate not fresh, I don't know if I should look at the control module below the radio(could it not be sending the right signal?) I see 3 wires in the schematics for the recirc motor I attached a photo of the schematics I am trying to use to figure out why the actuator won't change modes? Everything else works in the heat AC system (hot/cold) (vent switching) the rear system works great! Sorry if it was confusing I am at my wit's end with this up to today every one tells me it the actuator they don't seem to hear that I ripped the dash cover off and made my hands and arms bend in ways they should not to replace the actuator motor! I just need to find someone who knows how this actuator is wired and how to eliminate things without replacing good parts till it works again I have several volt/ohm meters and a 5mm bore scope to get into tight places I just need to know were to start and what to look for?

 

Thanks I am loosing sleep over this.

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this is the best I can show of were the acuator is located in the dash you can't see it but imagine about 3/4 toward the windshield and about 7-8 inches down and 18 inches from the passenger door down in that dark abyss is were it resides. under the defrost duct it was not something I was looking forward to at least if I have to take it to the dealer I can tell them it's not the acuator so they can't charge me 10 hours labor tearing the dash apart.

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Recirculation Operation
The HVAC control module controls the air intake through the recirculation actuator. The recirculation switch closes the recirculation door in order to circulate the air within the vehicle. The outside air switch opens the recirculation door in order to route outside air into the vehicle. Regardless of the blower motor switch position, recirculation is available only in the panel and bi-level mode switch positions. Including the OFF position. The mode switch must be placed in either the panel or bi-level position before the blower motor switch is placed in the OFF position. In order to reduce windshield fogging, outside air is circulated when the mode switch is in the defrost or defog positions. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times. If the HVAC control module detects a fault with the recirc door the HVAC control module will try to drive the actuator for a predetermined amount of time, to outside air, which is the defaulted position for the recirculation actuator.

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Thanks! Just found an explanation for the phantom recirc switching my truck has done since day 1, assuming my '07 retained the same setup. Haven't looked it over close enough to notice yet.

 

That always aggravated me. Seemed no matter where I set it, it would select the opposite automatically. Seems to be the way with me and electronics!

 

Our Volvo 940 has THREE high-side pressure switches. One for safety, one to control fan high, and one for fan low. Plus the one low side, of course, for a total of FOUR!

 

These things sat unused with air in the system for who knows how many years. Sat 1.5 years in my yard, and spent 2 months of one winter completely buried under 10' of snow while car was parked on dirt. Every one of them worked normally when I rebuilt the system last month. Some impressive quality components right there. :smoker:

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How I miss the days of levers and cables! My El Camino was over 40 years old, and every part of the HVAC system still worked.

 

Ain't electronics great? :nonod:

 

Since you're most of the way in there, you should be able to get to the wiring and test it to see if it's getting power, ground, and 5v reference - if that all checks out, the actuator motor is probably bad.

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There are 3 switches on my system 1 low pressure and 2 high pressure, my question was why does the system need 2 high cut outs? It is setup like this, the low is on the receiver/Drier, and high #1 is on the compressor high #2 is on the line between the condenser and orifice tube. Have 2 high pressure switches doesn't make sense, I thought it was a error in the schematics but I confirmed it on is on the back of the compressor and one between the headlight and condenser.

 

the first picture were the low side is 95 the engine was just restarted but the compressor will not restart because the low side switch was bad and was acting like a high pressure cutout above 80 psi! I replaced the low side switch and it has worked fine since! See photo #2 (this was right after replacement of the low/recycle switch)

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Yea one issue down now the recirculate door is my next task, then I have to replace both knock sensors :( that should be straight forward (fingers crossed) then I should be ready to hit the road in my travel trailer(I am planning on retiring in it roaming the country)

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Usually the one on the compressor is a safety one - it'll cut clutch voltage above a certain pressure threshold.

 

The other one could be to control the e-fans, if you have them. If not, could be a redundant safety - not sure there.

 

At least you had an easy fix there. Good deal.

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Stuff like this drives me friggin nuts. They should call that an "ILLogic circuit" ... :banghead: Thank GM for that brainstorm ...

 

I can't make heads or tails of these new diagrams. Looks like there's a diode there where you highlighted - not sure if that's what the symbol is now. Those should have voltage one direction (about half a volt) but ZERO in the other - I'd imagine a failed one having continuity in both directions would cause some strange issues. Could be a transistor of some sort, since there's "lightning bolts" next to it.

 

Sorry I can't be more help on this. When I run into stuff like this, I engineer a choke cable to manually open/close the flap. FIXED! :dunno:

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I know my post was long :( I already changed the actuator and the issue is still there :( what should be simple to diagnose is like brain surgery GM made this a whole lot more complicated than it needs to be! It's like why does it have 2 high pressure switches on the AC? I guess I will have to wait to get to a junk yard to pull a module and hope it's fixes it :) the closest junkyard is a hours drive so I have to plan the Trip.

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I did fix one issue I thought was either the compressor since the AC would work erratic when real hot out if I stopped to long, I replaced the orifice tube and drier and vacuumed it before recharging it but it kept acting weird turns out the low pressure(cycling switch) was bad it would not turn on the compressor if the low side was over 75 psi such as when I was running it hard and shut it down to run into a store for a few then the low side would be high without the compressor running, and it would not start again for 15-20 minutes until the system and equaled out, now it blows 36f out the front and 33f out the rear :) all the time now the switch was acting like a low and high cut out at the same time.

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A/C Pressure Sensors

The A/C system is protected by two pressure switches. The A/C high pressure switch interrupts the A/C request signal when the A/C line pressure exceeds 2896 kPa (420 psi). The A/C low pressure switch interrupts the A/C low pressure switch signal when the A/C line pressure falls below 145–172 kPa (21–25 psi). When the PCM sees an open in either signal, the A/C clutch relay control circuit is no longer grounded, thus shutting off the compressor. The low pressure switch will close when pressure reaches 262–290 kPa (38–42 psi).


Recirculation Mode

The recirculation door will move automatically with an input from the A/C high pressure recirculation switch at approximately 2413 kPa (350 psi). The PCM will place the A/C system in recirculation mode when a signal is sent over the A/C refrigerant high pressure cut-out switch signal circuit. The recirculation actuator door control circuit is grounded by the PCM to ensure that the actuator is forced to the recirculation position. This allows for the cooler inside air to flow over the A/C evaporator and cool the refrigerant, until the high side pressure returns to normal. This action will allow the high side pressure to return to normal pressure at a faster pace. The recirculation door will move back to the outside air position when the high side pressure reaches 1724 kPa (250 psi).

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Yeah they have some strange failures sometimes. At least yours didn't totally fail, causing the oil to slug the compressor. That's a fun one. Thing will just run and run and run, never cycling, bringing the low side pressure down so low that the evaporator freezes up, and turns the oil into molasses, starving the compressor.

 

Happened on my '94 K1500. I caught the problem before it became catastrophic, as I started to hear a clicking sound. I cycled the thing manually after that, but would occasionally forget. The R4 compressor that had in it didn't have much tolerance to slugging - thing got LOUD. About as loud as a jake brake on a fully loaded semi with straight pipes. :lol: Still cooled though! Ended up doing the entire system over. Was just as well, since the condenser was trashed, and all the fittings snapped off when I tried to remove them.

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Try this for starters

Recirculation Operation
When air recirculation is selected, a signal is sent from the HVAC control module to the recirculation actuator through the recirculation door control circuit. The recirculation actuator closes the recirculation door in order to circulate the air within the vehicle. The outside air switch opens the recirculation door in order to route outside air into the vehicle.

Regardless of the blower motor switch position, recirculation is available only in the vent and bi-level mode switch positions. Including the OFF position. The mode switch must be placed in either the vent or bi-level position before the blower motor switch is placed in the OFF position. In order to reduce windshield fogging, outside air is circulated when the mode switch is in the defrost, floor, and mix-blend positions. If the recirculation switch is pressed into the ON position when the mode switch is in an unavailable mode position, then the recirculation switch LED will flash 3 times.

When the recirculation door moves to a desired position, a variable resistor within the actuator is used to create the recirculation door position signal. The HVAC module uses the recirculation door position signal to determine the actual recirculation door position. The left instrument panel fuse block provides power to the recirculation actuator through the ignition 3 voltage circuit and the IP wiring harness junction block. Power and ground are provided to the HVAC control module by the fuse block through the ignition 3 voltage circuit and the ground circuits through the right instrument panel junction block. A 5 volt reference signal is sent to the actuator through the 5 volt reference circuit, through the right instrument panel junction block, to the recirculation actuator.

When the automatic setting has been selected, the HVAC control module will recirculate air whenever system temperature performance is insufficient to provide the desired temperature. The recirculation switch LED will not be illuminated. If either the outside air or recirculation switch is pressed during automatic operation, then automatic operation will be over ridden. The appropriate recirculation or outside air switch LED will be illuminated. The recirculation door will be opened or closed depending upon the selected override. When the ambient air temperature is below 4°C (40°F) the recirculation override of the automatic setting will only be available for 10 minutes.

When the automatic setting has not been selected, only the outside air or recirculation switch will be used to determine the recirculation door position. When the ambient air temperature is below 4°C (40°F) any recirculation selection will only be available for 10 minutes.

The A/C high pressure recirculation switch can cause the HVAC system to recirculate air. When the high side pressure reaches 2206–2620 Kpa (320–380 psi), the PCM will place the HVAC system in recirculation mode. The high side pressure is lowered when the inside air cools the refrigerant within the A/C evaporator. When the high side pressure reaches 1447–1861 Kpa (210–270 psi), the PCM will place the HVAC system out of recirculation mode.

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Thanks Tom but I have the manual climate control module, it doesn't have the temp based control the temp selection only moves the blend door to a set position based on were I have the knob set, I took the climate module apart today looking for broken leads or obvious damage but found none, it looks like they may have it designed to control to acuators position based on which one of 2 grounds is active? the acuator is really difficult to access I had to remove the entire top of the dash, the passenger airbag, just to reach it. I am going to try grabbing a used module from a upull it since new ones are no longer available and rebuild ones are insanely priced $150+ I hope it fixes it! I really don't want to to pay the local dealer to scan it with a tech 2 just to figure this out! I wish there was a shop in my area with a tech 2 scanner to get into the climate system for a resonable price, but we're I live there are only a few garages for the whole county that can be trusted our ac guy is booked for 3+ weeks and he's the only ac place that has a recovery machine not that I need one now :), I was hoping someone here had the same issue before and can tell me were to look for the problem?

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