Weird HVAC problem

[Slowrunner]

So I have a '05 SR5 V6. Normally, I can keep the inside temp. setting at 72 and be very comfortable, other than on a hot day, or a cold day, just to get the cab comfortable quick, but then 72 will do it. Last summer on a hot day it would work well and I would put it at around 68 most of the time. In December, while driving through Colorado, maybe 45 degrees out, I noticed at 72 it was blowing cooler air than I would have like...noticably cooler. Not a problem, just turn up the temp setting and the heater worked, just now 75-77was a better choice. In the spring once the weather started to warm up, I found that the thing worked great in the morning when the sun was coming up, but once it was up it would blow cold air all day. For example outside air 65, inside setting 72, cab felt comfortable but air coming out of the vents was cold enough you wouldn't want it blowing on the steering wheel. The dealership told me the computer was showing nothing abnormal, it wasn't a problem they ever see and I may just have to deal with it.
Now I know the air temp at the vents isn't the same as the temp it is trying to reach in the cab, but normally once the cab is at the temp, the air in the vents just matches it pretty closely. Now that summer is almost through, I haven't once set it below 74, and generally cruising on the highway for a road trip it is set at 77, still cold air coming out. I know this can't be right. I live in the desert, and I know I am probably the only person complaining that the air conditioning works too well, but I really can't get a comfortable temperature in my 'runner like I used to.
Anyone else have this problem? I'd like to have something to suggest to the service writer next time I take it in. My extended warrenty is out in about 10,000 miles, so I'd like to get a good paper trail on this thing now.
I feel like it could be a faulty sensor, computer etc. but maybe something mechanical like the blend door is jambed? Sorry for the long post, and thanks for any help you guys can give

 

[jharris2]

Have you checked the ambient temperature in the cabin to see how close the air temperature is to what you want?

The way the system was explained to me, it will do whatever the computer thinks is necessary to reach the temperature that is set. But instead of blowing air at the temperature you set, it cycles through warm and cold to maintain it.

Remember that the sun coming through the windows raises the ambient temperature, and body heat does, too. So it can be warmer than you think, meaning the system blows cold air.

In any case, it's definitely worth checking before the warranty expires. The system apparently has a computer that tracks a lot of data points and keeps them. Last time I had my system checked, the tech scanned the computer and found nothing unusual.

 

[drmorbius]

So I have a '05 SR5 V6. Normally, I can keep the inside temp. setting at 72 and be very comfortable, other than on a hot day, or a cold day, just to get the cab comfortable quick, but then 72 will do it. Last summer on a hot day it would work well and I would put it at around 68 most of the time. In December, while driving through Colorado, maybe 45 degrees out, I noticed at 72 it was blowing cooler air than I would have like...noticably cooler. Not a problem, just turn up the temp setting and the heater worked, just now 75-77was a better choice. In the spring once the weather started to warm up, I found that the thing worked great in the morning when the sun was coming up, but once it was up it would blow cold air all day. For example outside air 65, inside setting 72, cab felt comfortable but air coming out of the vents was cold enough you wouldn't want it blowing on the steering wheel. The dealership told me the computer was showing nothing abnormal, it wasn't a problem they ever see and I may just have to deal with it.
Now I know the air temp at the vents isn't the same as the temp it is trying to reach in the cab, but normally once the cab is at the temp, the air in the vents just matches it pretty closely. Now that summer is almost through, I haven't once set it below 74, and generally cruising on the highway for a road trip it is set at 77, still cold air coming out. I know this can't be right. I live in the desert, and I know I am probably the only person complaining that the air conditioning works too well, but I really can't get a comfortable temperature in my 'runner like I used to.
Anyone else have this problem? I'd like to have something to suggest to the service writer next time I take it in. My extended warrenty is out in about 10,000 miles, so I'd like to get a good paper trail on this thing now.
I feel like it could be a faulty sensor, computer etc. but maybe something mechanical like the blend door is jambed? Sorry for the long post, and thanks for any help you guys can give

Under the ignition key is a small air inlet. If you take off this panel you will find a piece of tubing that goes back to the blower and in the inlet to this tubing is a temperature sensing element (thermister). Mine was packed with dust bunnies and after I cleaned all the dust away from the thermister I noticed a large change in the the air temp coming out of the vents. I would suggest that you check and clean this area.:shrug:

 

[Kmvreter]

Under the ignition key is a small air inlet... is a temperature sensing element (thermister)... and after I cleaned all the dust away from the thermister I noticed a large change in the the air temp coming out of the vents. I would suggest that you check and clean this area.:shrug:

The good drm to the rescue! I second his suggestion.

Lately my fan speed was fluctuating noticably at lower speeds for short periods of time. Only noticed it after the cabin cooled down enough that it wasn't running flat out on HI. This thread reminded me of this sensor. Took it apart and cleaned the dust off with a Q-tip for the first time in 6 years. Makes a world of difference.

 

[Slowrunner]

Sorry for not responding quickly, but thank you guys for the suggestion, sounded promising and I tried it right away. To my surprise the sensor was very clean visually, but since I was that far I cleaned it off anyway, no luck. So I still have not set the thermostat under 72 this summer and its been 90-100* everyday. Hopefully it will blow warm air come winter. It is due for an oil change soon so I will have them check it out again. Thanks again