Since completing the heater core and evaporator install, I had the AC system recharged at a local shop. The tech told me the low side pressure is 30 psi. In 85° weather, I'm getting 55-60° air from the center vent w max-air and full fan. Quite frankly, I was warm. Before all this, my truck AC would freeze you out! I read the article at http://articles.mopar1973man.com/2nd-generation-24v-dodge-cummins/27-hvac-heating-ventalation-and-air-conditioning/58-recharging-air-conditioning-with-r134a-freon and noticed the performance temperature specs were exactly what I'm now getting. Is it unreasonable to expect my system to be as cold as it used to be? If its not unreasonable, what do I do to get my cold temps back? Although my blend door is stuck, I'm certain it is stuck in 'cold' position.

The first thing to check is the compressor suction line coming out of the evap. Is it cold? Beer can cold? If it is then you are getting warm air mixed with the cold air (blend door). If it is warm and the compressor is cycling then the system is a little low on refrigerant. With a normal charge in warm weather and the engine at an idle the compressor should be running just about all the time.

I'll check that tomorrow afternoon.. Should be close to 90°.

Thank you.

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Checked the line as you suggested. It was "beer can cold". But here's why I don't think the blend door is the culprit. One morning, After the truck had sat all night, I drove it to work using vent air only - no AC. I took temp of vent air. Then after the truck had warmed up to 190°+ for several minutes, I checked the vent air temp again. There was only a 2° increase. That tells me the blend door is not allowing any significant warm air into the vents.

I'm headed to Florida next week. I sure would like to lower the temp a few degrees.

So check the hi and lo side pressures with a manifold gauge set.Lo side should see about 35-40 PSI. Hi side will vary on outside temp bout typically I see about 200-250 PSI on a warm to hot day.