My 1984 300SD puts out 76 degree air at 65 mph on a 99 degree day with 40% humidity. Should it be colder than that? I am running the air conditioner at multilevel and the air is blowing through the defrosters, foot vents, and front panel vents. The blower is at high speed with the climate control set at min. It is also taking fresh air rather than recirculating the air. In the normal mode, the air blows through the defrosters and foot vents only.

What can I do to fix this?

It's time to pull out the ol Miti-vac and start doing some vacuum control testing. With it using fresh air at this temp, that is probably as cool as you're going to get.

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1971 R600 Mack toterhome (SuperDawg)
99 NU-WA Snowbird 34+2 SE 102 5er
If it's not diesel, it's not in my stable!
53 F100 617.951/auto
95 Dodge 3500 Cummins/5 speed service truck

You have a vac leak -- you should only get air out the center and side vents in "normal" mode.

Check the heater hoses for hot on the exit side -- if the hose is hot when the temp wheel is at the click stop cold side, your monovalve is leaking and giving you heat when you don't want it.

Also, check the sight glass on the receiver/dryer for bubbles -- if you see any, you are low on charge, too.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

My 1, 3, 5 vacuum actuators will not hold a vacuum. Looks like I will have to go to the junkyard to get some good ones. I can see that 99 degree air will not cool as well as recirculated air.

My charge seems to be fine. (I am using Duracool, but works better than the 134a that was in it.) It may be a little overcharged.

I don't think the mono valve leaks that much, but the main problem is the fresh air door.

For now, I will try to close the fresh air door until I get new vacuum actuators. I could smell the cigarette smoke from the car ahead with the air conditioner working.