Strange A/C phenomenom

[SND2010]

I just purchased a very clean 2010 SLT Crew Cab. I was driving it home from the dealer (125 miles) and I noticed that when I was stopped or moving slowly in traffic the volume of air blown through the A/C ducts seemed normal and cool. However when I was at highway speeds (75) the volume of air coming through the ducts was almost nothing. The fan speed seemed the same and I had all of the windows up.
When I slowed down again, the higher duct air speed returned.

I have only had the truck for a few hours and haven't had a chance to check the A/C pressures yet, however I will do this tomorrow.

Does this behavior ring a bell with anyone?

Thanks...

 

[MRFREEZE57]

it could be low on refrigerant and causing the evaporator to ice up. did you try turning off the AC compressor and leave the fan running for about 5 min, then re start the compressor and see if is blowing cold air. you need to get a set of gauges on the system to see what is going on.

 

[csuder99]

Does the air come out the defrost or the foot area when that happens ?

 

[indept]

Sounds like a blend door issue in the dash

 

[Fast69Mopar]

I just purchased a very clean 2010 SLT Crew Cab. I was driving it home from the dealer (125 miles) and I noticed that when I was stopped or moving slowly in traffic the volume of air blown through the A/C ducts seemed normal and cool. However when I was at highway speeds (75) the volume of air coming through the ducts was almost nothing. The fan speed seemed the same and I had all of the windows up.
When I slowed down again, the higher duct air speed returned.

I have only had the truck for a few hours and haven't had a chance to check the A/C pressures yet, however I will do this tomorrow.

Does this behavior ring a bell with anyone?

Thanks...

Without seeing the gauges hooked up my guess is that the evaporator is freezing up due to low refrigerant level.

If you don't have the opportunity to connect a set of gauges to the truck, the next time the airflow gets low, press the snowflake button to turn the compressor off and continue to drive. If the airflow starts to feel normal again the the evaporator is freezing. The airflow will get better when the evaporator begins to thaw.

 

[danoday]

If you engage the AC. Pop the hood while at idle. You should hear an audible clicking noise every minute or so. That's the AC compressor, if it's not clicking or engaging then you need refrigerate.
If it's a cabin fan airflow problem, good luck.....lol

Sent from my SAMSUNG-SM-N910A using Tapatalk

 

[SND2010]

OK, finally got out the gauges... The system had about 22 PSI when I started the work. My AC chart says that at 80 degrees (F) the low side should be 40-50 degrees. It was 82 (F) in my driveway and I added 14 oz. of R134a and brought the low side pressure up to 42. The system was blowing plenty cold. I also thoroughly checked the AC box and found that the blend doors are working properly but my blower resistor was bad (ie. no fan on position 2, Pos 1,3,4 work fine), Blower motor is ok. My high side gauge has a stuck valve so I didn't check the high side like I should have.

I haven't had a chance to re test the system at highway speeds (75) where I first noticed the cooling issue. I will try and get to that very soon.

 

[SND2010]

Today I replaced the blower motor resistor. Part of it was rusted completely through. This fix restored my fan control speed#2 which was dead.