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Discussion Starter #1
I have an 08 Pilot EX-L with about 160K miles. I've owned it for just over two years and the majority of the use is a fairly short commute to work or local errands. The A/C has always worked, but recently I've been doing some longer trips in hot weather and discovered that apparently the A/C does not work as well as it should. Over the course of an hour of driving the air coming out of the vents just keeps getting warmer and warmer and finally gets to the point where it really isn't much cooler than the outside air. I know that when I park it after one of these drives, plenty of water drips down under the car, so I'm assuming that the system is "icing up", or something like that. I used to know more about this stuff when I was younger, but I'm getting old enough where I usually just take it to a mechanic and tell them to fix it...

I'm planning on taking it in to my favorite mechanic this week to have it fixed, but I'm wondering if anyone can identify common issues that should be investigated or parts that may as well be replaced if they end up tearing into the system anyway. I suspect that the refrigerant needs to be recharged, but that often points to the fact that some other piece may be failing and allowing it to escape.

Thanks for any input!
Bob
 

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Sounds like a freezing evaporator coil due to low refrigerant level. Your mechanic needs to do a leak test to find the leak and fix the system. Just putting in more coolant will be a temporary fix and you will be dumping coolant into the atmosphere.
 

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Pardon @Daltongang as he has several young voluptuous front heavy bikers zipping pass him but refrigerant would be more accurate term.
Get the refrigerant levels checked, look for leaks and look over the condenser which may have damage.
 

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Pardon @Daltongang as he has several young voluptuous front heavy bikers zipping pass him but refrigerant would be more accurate term.
Get the refrigerant levels checked, look for leaks and look over the condenser which may have damage.
"Freon is the cooling agent used in most air conditioning systems. Every air conditioning system needs a refrigerant (also called a coolant) that actually creates the cool air -- that's the role of Freon"


 

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Probably improper refrigerant level but I would make sure the cabin air filter is clean first if you have never changed it. If it is low on refrigerant the best course of action is to find the leak but that is not always the cheapest option. Since you really don't know if this is a very small leak that has lost refrigerant over 12 years or a bigger leak that has lost this refrigerant over the two years you have owned it, you might consider just topping the refrigerant level back to where it should be and see how long it take to leak down again. If I were in the situation you describe that would be what I would do if I owned it. I would also put some dye in the system when I topped it off to help identify the leak more easily.
 

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Discussion Starter #7
Update / additional thoughts:

I replaced the cabin air filter with my last oil change, so I don't think that's a problem. I did realize that in my initial description of the problem I failed to note that the blower fan for the rear seat passengers does not work. Is it possible that because that fan doesn't work, the A/C system may not be working properly due to lack of proper air flow?

I have been meaning to fix the rear fan, but haven't got a "round tuit" yet.
138223
 

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Rear blower thermistor (aka thermal resistor aka transistor). Just did this and that was the cure.

138234




But start by seeing if just cleaning the rear blower motor fan with a vacuum cleaner might do the trick. To clean the rear blower fan, remove the driver's side panel under the center console between the driver's seat and the gas pedal. The panel just snaps out and it's easiest if you start pulling near the gas pedal.

138235





Thermistor installation tips:
  1. Remove wiring harness connector.
  2. Depress little black metal tab just outside housing and rotate old thermistor clockwise so notches align and it pulls straight out easily.
  3. Install new thermistor by sliding in and rotating counterclockwise so notches no longer line up.
  4. Rebend little black metal tab to hold thermistor in place if necessary. It should snap into place.
  5. Reconnect wiring harness.
  6. Test. If it works you've just saved hundreds of dollars.
 

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Discussion Starter #9
I popped the cover off the rear blower fan. Certainly some dust build up, but I don't think it was completely blocking the air flow. I cleaned it up and tried turning it on, but the blower just wiggled like it got power for about a half-second, then quit. I disconnected the transistor and tried again and it didn't even wiggle.

I ordered a (cheapo) replacement from Amazon and it should show up Wednesday. We'll see if that will fix the problem at that time. I have an appointment on Thursday to get the A/C inspected/repaired.
 

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Update / additional thoughts:

I replaced the cabin air filter with my last oil change, so I don't think that's a problem. I did realize that in my initial description of the problem I failed to note that the blower fan for the rear seat passengers does not work. Is it possible that because that fan doesn't work, the A/C system may not be working properly due to lack of proper air flow?

I have been meaning to fix the rear fan, but haven't got a "round tuit" yet. View attachment 138223
Yes, no airflow = freeze up
 

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Discussion Starter #11
Updates:
  • I replaced the resistor for the rear blower fan and that got the fan working again. Yay!
  • I just got a call from the shop and they said the A/C charge was a bit low, but not excessively low. They feel it may have just been low enough that it allowed the system to ice up gradually and once the ice buildup was far enough along, it just went into a vicious spiral until no cold air was being allowed to reach the interior.
Tomorrow I will be making the same hour+ run that previously created the problem. It won't be quite as hot as the last time I made the trip, but it should be close enough to know if the problem still exists.

After I fixed the rear fan, I was testing the various settings. I never looked in the owners manual regarding the rear heating/cooling controls (my bad), but I always thought that when I gave control to the rear passengers, that knob controlled fan speed. I discovered that it doesn't control fan speed (other than the ability to turn it off), rather it just gives the rear passengers the ability to control the temperature of the air coming out of the vents. It's amazing what you can learn if you actually take the time! o_O
 

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After I fixed the rear fan, I was testing the various settings. I never looked in the owners manual regarding the rear heating/cooling controls (my bad), but I always thought that when I gave control to the rear passengers, that knob controlled fan speed. I discovered that it doesn't control fan speed (other than the ability to turn it off), rather it just gives the rear passengers the ability to control the temperature of the air coming out of the vents. It's amazing what you can learn if you actually take the time! o_O
Glad switching out the thermistor fixed your rear blower motor.

As for the subtle difference you found in how the rear AC / heater control knob works, great! To add to the confusion, it works like you initially assumed on the LX model and how you describe on EX and EX-L models. Furthermore, this subtle difference in wording, which I've highlighted in the attached excerpt from the Owner's Manual, appears on two different pages, so by the time you read the second one, the human brain has a tendency to anticipate it's the same as the previous one.

However, what still confuses me is that for the EX and EX-L models, the Owner's Manual reads:
Cool Air​
Turn this dial​
counterclockwise to increase the​
temperature.​

Shouldn't it be:
Cool Air​
Turn this dial​
counterclockwise to decrease the​
temperature.​


Guess it's up to us to test this out and post results. :)
 

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Glad switching out the thermistor fixed your rear blower motor.

As for the subtle difference you found in how the rear AC / heater control knob works, great! To add to the confusion, it works like you initially assumed on the LX model and how you describe on EX and EX-L models. Furthermore, this subtle difference in wording, which I've highlighted in the attached excerpt from the Owner's Manual, appears on two different pages, so by the time you read the second one, the human brain has a tendency to anticipate it's the same as the previous one.

However, what still confuses me is that for the EX and EX-L models, the Owner's Manual reads:
Cool Air​
Turn this dial​
counterclockwise to increase the​
temperature.​

Shouldn't it be:
Cool Air​
Turn this dial​
counterclockwise to decrease the​
temperature.​


Guess it's up to us to test this out and post results. :)
These instructions aren't to confusing! Lol
 

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Discussion Starter #15
Final resolution update:
I made two 100+ mile runs over the last two days and the A/C worked perfectly. It wasn't quite as warm as the days when I had the problems, but it was close enough to call it a successful fix. Yay!

While making the run, I was alone in the vehicle so I was able to play with the rear controls to see what I could determine. As near as I can tell, turning the knob counterclockwise makes it colder and clockwise makes it warmer. It was kind of hard to tell on the cooler side because at the time I was playing with it, the system was pretty much running at max cool and so I couldn't really tell if the temperature of the air coming out of the vents was changing that much. When I turned it to the warming side I could definitely tell that the air got warmer as I turned the knob clockwise. I am really just assuming that the air would get cooler when you turn the knob counterclockwise.
 

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Final resolution update:
I made two 100+ mile runs over the last two days and the A/C worked perfectly. It wasn't quite as warm as the days when I had the problems, but it was close enough to call it a successful fix. Yay!

While making the run, I was alone in the vehicle so I was able to play with the rear controls to see what I could determine. As near as I can tell, turning the knob counterclockwise makes it colder and clockwise makes it warmer. It was kind of hard to tell on the cooler side because at the time I was playing with it, the system was pretty much running at max cool and so I couldn't really tell if the temperature of the air coming out of the vents was changing that much. When I turned it to the warming side I could definitely tell that the air got warmer as I turned the knob clockwise. I am really just assuming that the air would get cooler when you turn the knob counterclockwise.
I am having the same problem with my 04 EXL-RES. I set it at the lowest 68F and gets cold minimally, less on hot muggy days. It was working fin last summer. Wondering if this is the same fix? Do you have a part number you could share for this thermistor?
 

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Discussion Starter #18
I am having the same problem with my 04 EXL-RES. I set it at the lowest 68F and gets cold minimally, less on hot muggy days. It was working fin last summer. Wondering if this is the same fix? Do you have a part number you could share for this thermistor?
Just to be clear, I really had two separate issues. The blower fan that blows air out of the vents for the rear seat passengers was not working. I bought the resistor to fix that. Here's the part on Amazon that I purchased:

I don't believe that the rear blower motor not working actually affected the ability of the system to cool my Pilot. The system is designed that the rear blower motor can be turned off independently of the front, so I don't think it's a requirement that the rear blower actually works.

My A/C system was also a bit low on refrigerant and that's what caused the system to gradually ice up and quit blowing cold air into the car. I brought mine to a shop and had them check it and as far as I know they just added refrigerant and did not do an extensive diagnostic to see if they could find a leak. Yours may have a leak serious enough to warrant more work.

Hope this helps!
 

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Just to be clear, I really had two separate issues. The blower fan that blows air out of the vents for the rear seat passengers was not working. I bought the resistor to fix that. Here's the part on Amazon that I purchased:

I don't believe that the rear blower motor not working actually affected the ability of the system to cool my Pilot. The system is designed that the rear blower motor can be turned off independently of the front, so I don't think it's a requirement that the rear blower actually works.

My A/C system was also a bit low on refrigerant and that's what caused the system to gradually ice up and quit blowing cold air into the car. I brought mine to a shop and had them check it and as far as I know they just added refrigerant and did not do an extensive diagnostic to see if they could find a leak. Yours may have a leak serious enough to warrant more work.

Hope this helps!
Thanks. I want to try the easy fix first. Ill verify that the back is working or not. Kids in the back haven't complained that it's not working.

One thing I have been seeing on YT is that the system needs to be evacuated when adding refrigerant, otherwise more problems down the line. I am not sure I want to get into all that as I don't have a pump and accessories. Did they do this for you?
 

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Thanks. I want to try the easy fix first. Ill verify that the back is working or not. Kids in the back haven't complained that it's not working.

One thing I have been seeing on YT is that the system needs to be evacuated when adding refrigerant, otherwise more problems down the line. I am not sure I want to get into all that as I don't have a pump and accessories. Did they do this for you?
Evacuating the a/c system of moisture is important whenever the system has been opened up to replace components. I've purchased my a/c gauges and vacuum pump from HF and had a successful repair on my Avalon a/c compressor, drier before recharging with refrigerant.
 
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