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2010 ac only blows cold air sometimes

wakebdr

Full Member
Joined
May 25, 2006
Messages
264
Location
Cumming, GA
My 2010 LTZ AC is acting up.  Sometimes it will blow cold air, sometimes it won't.  I got one of those AC Pro things hoping that would fix it.  The pressure on the low port was fine so I didn't add any.  The compressor runs, but it just blows warm air sometimes.  Where/what do I need to check next?
 
Blend door actuator?
 
EXT4ME said:
Blend door actuator?

OK, I've looked up what that is, but I'm unclear on a couple things.  Are there multiple blend door actuators in the vehicle?  Is there a way to test it?
 
Well I take that back.  Sitting in a parking lot waiting for my wife and decided to pop the hood to take a look.  Compressor wasn't running.  Then it clicked on for about two seconds and stopped again.  Should the compressor be on all the time if I have my air set on 60 and it's 80 outside?
 
Sounds like you are low on Refridgerant or have bad low pressure switch.

Suggest going to good AC mechanic.
IF low you need to find leak and repair.
 
Had the same problem in my '07.  First I recharged the system and didn't help.  Then I replaced the pressure switch (https://shop.advanceautoparts.com/p/factory-air-system-mounted-cycling-pressure-switch-37308/18893472-P) and it worked great for about a week then started doing the same thing.  Finally took it to a good A/C mechanic and they used a dye to find a leak in the condenser.  Once that was replaced it has worked great since.
 
If the compressor is clicking on and off it's almost certainly low and needs a recharge. Mine was acting the same way and provided no cold air. Dealership did a recharge and added a dye to determine if there's any leaks. No leaks were found so they told me to keep an eye on it. Been only a few weeks but still blowing freezing cold!
 
So it was just blowing ice cold on the way home from the store just now.

Is a recharge the same thing that the DIY AC Pro stuff is for?
 
Is the A/C kicking on even when the button isn't lit up?

If your compressor isn't kicking on and off constantly then I'd say you've got another issue going on. It could be as simple as a failing Ambient Temp Sensor (located right above the driver's head in the headliner). Have you noticed any issues with heat output recently or strictly A/C?

As far as the AC Pro type of stuff, theoretically they're the same, but personally I would never trust the gauges on those cheap things.
 
wakebdr said:
So it was just blowing ice cold on the way home from the store just now.

Is a recharge the same thing that the DIY AC Pro stuff is for?

If you are getting "ice cold" air randomly, my guess would be the refrigerant charge is most likely close to being right.

Do not go and just add refrigerant to try and chase down an unknown a/c issue.

Having too much refrigerant can cause it's own set of problems, possibly even damaging the system if way too much is installed.

If the actual problem extends beyond a user changeable part, like a sensor or a blend door actuator, a/c repairs are usually best left to someone with the tools and experience to properly diagnose and repair the system.

Without the proper tools, it would be very difficult to evacuate the refrigerant, pull a vacuum on the system, check for leaks, replace parts and properly recharge the system again to the exact level of refrigerant for correct operation.

Some DIY'ers are capable, but I would imagine most are not.

I know I'm not.

Some things are best left to the qualified for proper repair.

A/c systems are one of those. IMO.

 
I've had two friends who know more than me tell me I need to replace the blend door actuator.  However, when researching them it looks like there are multiple part numbers and multiple actuators in the vehicle.  Anyone know what part number I need to look for?
 
If you have dual zone climate control then you have 2 blend doors. Plus a re-circulation door. Good news is they probably don't need to be replaced -- odds are the sensor contact wiper inside the actuator needs to be cleaned. The actuator is greased at the factory and eventually some grease makes it's way onto the sensor. It tells the computer the position of the door and if the computer loses that signal, the door is locked in the current position.

The bad news is they are a b i t c h to access, at least on my 2004. Actually the driver's side one wasn't too bad, can be accessed from under the passenger side dash. But the passenger side one (and the recirc one) require complete disassembly of the dash to access them.

All that said, if your compressor clutch is not engaging even though the AC is turned on and the temperature is above freezing, then there's an issue in the cooling system. Intermittent operation like you describe may be as simple as excessive clearance in the compressor clutch. As they wear the gap increases. Eventually the gap is wider than the electromagnet can overcome. But a bump or facing uphill can give things just that extra little nudge so the clutch engages -- for a while. The gap can be adjusted, but requires a compressor clutch adjustment tool and may be too rusty to move.

As for AC pressure: AC pressure tells NOTHING about the state of charge. If there is ANY liquid in the system, even just a drop left, the pressure gauge will show the vapour pressure of the refrigerant at the ambient temperature and will be the same as if there was 20 ounces of liquid in there at that temperature. IE: pressure = temperature, not quantity. AC gauges should have temperature equivalents printed right on the face, or you can google a temperature/pressure conversion chart. The low pressure gauge should show the ambient air temperature when the system is off, and cycle down to no less than about 2?C (34?F) when the compressor is running. If it gets that low, then the compressor should kick off until the pressure rises to ~30?C. That is just about the ONLY thing a cheap low pressure gauge from a kit is good for.

Quantity can only be determined by weight. Evacuate the system and weigh how much is recovered, or fill with a known weight of refrigerant is the correct way to fill the system.

One can approximate the correct fill by comparing the temperature of the line going into the evaporator to the line coming out of the evaporator -- they should be equal when the compressor is running steady. If the line coming out is warmer then there is no residual liquid exiting the evaporator and the charge is probably too low. If the line and accumulator are frosted over, then it is probably overcharged and you run the risk of liquid getting to the compressor. Since liquid cannot be compressed, this qualifies as a Very Bad Thing.

Bear in mind that if you lost your refrigerant, there is a very good chance that you also lost your lubricating oil since it is carried around the system by the refrigerant. Charging the system indiscriminately could mean running the compressor dry and dry compressors don't last long. There are little testers that are pressed on the low pressure valve with the system running and can give an idea of the oil concentration in the refrigerant. In general, it is better to have too much lubricant than too little. Too much will reduce the cooling capacity, but at least the compressor will survive.

If the system pressure leaks down to 0psi, one must assume that moisture can enter and the system will require a long hard vacuum at least and if it sat at 0 for any length of time the accumulator (which contains the dessicant) should be replaced.

Finally, beware of kits marketed to do-it-yourselfers that contain sealants. They rarely work as advertised and some can ruin your system. The ones that claim to cure seal leaks aren't too bad, but any sealant that claims to fix holes in the metal parts generally leads to "Black Death" if it meets any moisture in the system and the entire system will have to be replaced.
 
Two times I have had a problem with intermittent cold air and failure of the compressor to (intermittently) run on my 2001 Blazer which has the same basic A/C system.  Both times, I found compressor oil in the low pressure cycling switch and replacement of the $10 switch cured the problem at least for a couple of seasons.  This is a switch that is on a Schrader valve and is replaced without discharging the A/C system.  My system probably has too much compressor oil or the wrong type, but the actual repair alternatives cost far more than $10 - so I just replaced the switch again. 

Just unscrew the switch from the accumulator (in front of the evaporator core) and see if oil drips out of it.  If it does, then simply screw on a new switch and see if problem goes away.
 
Got out there to take a look at the actuator.  I don't know how it's supposed to operate, but it didn't seem like it was operating correctly.  I took a video of it, but it didn't move until I took the temperature up to 90 degrees.  Then when I took it back down to 60, it adjusted again.  However, i manually adjusted whatever the actuator would be moving and never really felt a difference in the temperature of the air coming out of the vents.  So, to my untrained eye, it doesn't look like the actuator was working correctly.  But with the actuator not installed and me manually adjusting, it didn't seem like it affected the temperature of the air either.  So it looks like there may be multiple things going on.

Video: https://photos.app.goo.gl/zQftbV1kjFbTxtYQ8
 
Little more info.  Family and I went into town just now.  When I turned the passenger climate control on, the passenger side blew cold air but the driver and rear air stayed the same.  How many actuators are in the vehicle?
 
So I guess the driver side actuator controls the rear also?

I think I misunderstood what the actuator does.  I thought it controlled the temperature of the air, but it sounds like it opens and closes something that allows the air the flow properly.

Why would I be getting cold air on the passenger side, but not on the driver side if I have what the actuator controls open?  I obviously have very little knowledge on what I'm talking about so please be as specific as possible in any answers.  ELI5
 
Ok, the actuator controls the temperature by blending hot air (from the heater core) with cold air (from the AC evaporator). All air passes through the AC evaporator first, to remove humidity, then it is re-warmed as needed by passing some air through the heater core.

If you set the air temperature to the hottest temperature setting available, the system will pump all air through the heater core. If you select the coldest possible setting, no air will pass through the heater core. In between, sensors monitor the cabin temperature, duct temperature, sun load, etc. and the climate control computer calculates the optimum blend and fan speed. I believe the rear is fed from the DS ducting. The passenger has a separate blend door in dual-zone systems. There is also a third actuator that controls the blending of fresh outside air with recirculated inside air (max AC modes generally try to recirculate pre-cooled inside air) The passenger and vent actuators are buried deep in the dash, very difficult to access.

The actuator contains a motor, driven by the computer outputs, to move the blend door and a sensor to tell the computer what the current door position is. The sensor consists of a resistive material swept by a brass (IIRC) contact tied to the output shaft, so the resistance changes as the door is moved.

The actuator is heavily greased. If grease migrates onto the resistive strip, between the strip and the contact, the resistance will change and may actually become infinite. At this point the computer throws up it's metaphorical hands and says "damned if I know what to do now", locking the door in whatever position it happens to land in -- usually hot.

Each time you cycle the key, the computer tries again. So in the early stages, the problem may be intermittent. Eventually there's too much interfering grease and it never works again.

Unless there is a physical problem with the actuator, the fix is easy. Carefully open the actuator case (several tiny flat screwdrivers and an extra pair of hands may be beneficial as you release all the plastic tabs) and gently clean off the excess grease from the sensor. I like to use a Q-tip or tissue soaked in brake cleaner for this sort of operation. Leave some grease on the gears though.

Reassemble, reinstall, and test. Clear as mud?
 
Wow!  That was an excellent reply.  Thank you so much.

I opened the actuator yesterday but didn't know what I was looking for.  Which part is the sensor in there?  If I were looking for it, is it obvious?
 
A picture is worth a thousand words. Look at this video, starting at 2:10
https://www.youtube.com/watch?v=XluNt-e3QAI
 
Opened up the actuator and cleaned the grease off the sensor.  Hopefully will get some time to today to put it back in the truck and give it a shot.  Keeping my fingers crossed that this solves it.

Thanks so much for the information.
 
As an aside, I have found that sometimes when I have disconnected the battery in my truck, the blend door actuator (and also my sun roof) tend to forget their settings and limits.

I have found it best to make sure I completely have my a/c system turned off before removing the battery.

When I have done this, the blend door actuator tends to "reset" itself properly the next time I start the truck and turn the a/c system back on.

My sunroof must be cycled to all extremes of travel for it to reset properly, but that's another story.

What I have described concerning the a/c system has been referred to many times in this forum.

Some call it a relearn of the blend door system.

When I have forgotten to do this relearn, my a/c will sometimes do the "blowing hot air out of the driver's side dash vents" thing, until I go back and do the relearn procedure.

Just a thought.
 
Cleaning the grease off didn't seem to do anything.  Have a new actuator being delivered today, so hopefully that will get it.  If not, then I guess I'll try to find a good AC shop.
 
Put the new actuator in last night and went through the calibration procedure.  Ice cold air was flowing.  Today...different story.  Still off and on cold air.  So it must be something else going on now. 
 
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