Vehicle is an '09 Acura MDX. Driver side vents started blowing hot, passenger side and rear AC unit are ice cold. Before taking it in I checked relay, blend doors, refrigerant levels look good (only tested with the pressure gauge on a $40 bottle of R-134a), and couldn't see anything else out of whack. My guess was expansion valve, but that's where my knowledge and equipment come to end, so decided to take it to a reputable shop.

They found some dye from their leak test on the AC compressor discharge line crimp fitting, so looking at replacing that and recharging it. Quote came out to right at $1k after repairs and diagnostic fee. That check out or am I paying someone's bonus? Seems like a steep cost for what looks like a $40 part.

I'm starting to think it's time to take her out to the pasture.

Probably need to check high pressure and low pressure readings with an a/c gauge set. Get a cheap backlight flashlight and look for leaks as glowing green spots on all of the a/c parts. If you have a leak and the high pressure side is low, it could explain your symptoms. $1000 seems high to me, but renting the equipment to vacuum, store, and recharge the refrigerant can be a few hundred.

GrapevineAg said:

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Probably need to check high pressure and low pressure readings with an a/c gauge set. Get a cheap backlight flashlight and look for leaks as glowing green spots on all of the a/c parts. If you have a leak and the high pressure side is low, it could explain your symptoms. $1000 seems high to me, but renting the equipment to vacuum, store, and recharge the refrigerant can be a few hundred.

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High side read 150psi, low side read 30 psi. The only part with any kind of leak was at the AC compressor discharge line. Didn't look like a big leak with their pictures.

Ribeye-Rare said:

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Average Joe said:

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Driver side vents started blowing hot, passenger side and rear AC unit are ice cold. Before taking it in I checked relay, blend doors, refrigerant levels look good (only tested with the pressure gauge on a $40 bottle of R-134a)

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My money would be on re-checking the driver's side air mix motor (that's what Honda calls it).

I'll bet either that motor has a stripped gear, or perhaps the driver's side temp sensor has gone bad and is telling the door to give heat.

I really doubt you have a refrigeration system problem since you're getting ice cold air elsewhere (plus you've checked for a low charge). The front driver's side and passenger's side share the same evaporator so I wouldn't suspect an expansion valve either.

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Everything I know points to the air mix motor, as well, but I could see all of the motors on both sides moving as I turned the temp all the way up and back down. So, unless they are moving, but not moving the part behind them then I'm not not sure what the problem could be.

I did check the pressure, but only on the low side. I don't have a gauge to check the high pressure side. The pressures from the mechanic were 150psi on the high side and 30psi on the low side. So, it looks like the high side could be borderline low. I'm uncertain how that would allow for the passenger side to be cold and driver to be hot, though.

Many Lexus vehicles have this same issue with the problem being a Servo Motor. However, they typically just need to reset or reprogram the motor as opposed to replacing the part. These SM's are located behind the dash board depending on whether it's on the driver or passenger side that's not blowing cold. So replacing the part is not easy but dealerships can reprogram easily but typically charge around $200ish.