OK, so normally my fan speed is fine, but after driving about an our it starts to weaken, and at 6+ hours weakens significantly. The air is cold, so no problem there, and I can hear the fan blowing like crazy, but not much is coming through the vents, almost like it's being re-routed somewhere else.

And before it's suggested, the cabin filter is new, and all vents are turned off except the ones facing me (I'm driving alone). Also, there is a difference in air-speed between recirculating and fresh, but it's not as much as it should be IMO (kinda' like when vtec kicks in lol).

Posting this thread because all the others I found were a cabin filter issue, or didn't say anything about blowing fine until the car has been on the highway for a while.

Sounds like a vacuum issue to me, and I'm at a loss on anything else since it works perfectly on short trips.

ANY helpful info is appreciated.

 

Probably condenser freezing up. It's happened to me on long trips. Make sure it's not running in re-circulate mode. And I just turned of A/C (punch the A/C button on the right side) and let outside air circulate for about 30 minutes. Usually that does the trick.

 

Interesting. And the air still blows cold for you? And I'm talking 95° outside, the condenser can still freeze?

 

Yeah, all has to do with moisture from the air freezing. Has happened to me a few times, sometimes even when the relative humidity didn't seem too bad.

 

OK, sounds plausible. However, I don't ever remember it happening when the car was new, or even for years after that. Maybe there is something additional going on?

 

I need to correct myself: It's actually the evaporator that is getting iced up on the exterior due to moisture.

It's possible the expansion valve is going bad. IIRC, it has a temp sensor in it that is supposed to shut off the compressor if it detects icing conditions. That's not a cheap replacement because the system will have to be evacuated and refilled after the valve is replaced.

 

80560-SDN-A01 $28.23/$21.17 (Thermistor)
To remove:
Remove pass. lower cover
Disconnect 4P connector from the transistor
Remove self tapping screws
Remove transistor
Disconnect 2P connector from evap temp sensor
Remove connector clip
Remove self tapping screw and pull out sensor.

Test sensor
Dip sensor in ice water, measure resistance between its terminals
Pour warm water on sensor and check for change
32 degrees resistance 32k
86 degrees 9k

Pg. 21-66 FSM

 

Ah, it's separate from the expansion valve. Good to know!

I wonder if that will resolve his issue? Will be interested to hear the test results if the OP chooses to do so...

 

Whoa, interesting.

 

Mine was doing this. Took it in and it was a little low on freon, filled it up and its been fine and I just went on a 16 hour roadtrip. Guy at the dealer said it is very rare that the expansion valve goes bad.