AC PROBLEMS 300D 1978

I AM HAVING PROBLEMS WITH MY AC THE COMPRESSOR IS ON TEMP AT 65 BUT IT IS BLOWING OUT HOT AIR THE TOP VENTS BLOWING HARDER THAN OTHERS LIKE HEAT IS ON
BUT IT IS NOT. COULD U PLEASE TELL ME WHAT TO LOOK FOR
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I'd ask Tiger about this one but my guess is the vacuum actuators under the dash (somewhere) are not operating properly. Have a similar problem on my '81 300D and still haven't gotten up the guts to open things up under the dash.. Does yours have mechanical levers, etc., on the center console for the heater/AC settings? Also, if the compressor is engaged check the AC line going across the front of the engine to see if it is cold. If not you have a more serious situation, or perhaps the system is simply low on R12 or R134A if you've converted. My '81 240D is mostly mechanical and works much better than the '81 300D.

ON
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The logic board has a solder crack is is acting illogically!
The logic board or "amplifier" is located behind the glove box - remove it to access the amplifier which is attached to the firewall. It's about the size of a cigarette pack and has a perforated black cover.
These can be bought for about $100, exchange.
If the car's servo is old it might make sense to look at a new digital system, available from Performance Products, that replaces all this old junk. It's a $700 permanent fix.
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I would do basic check for all functionalities... When you turn on A/C, touch the fatter freon line... is it icy cold? You may have to wait five minutes with all windows closed... or if it is cold out there, leave it open. If the line is cold, then you got enough freon... if not, you are low or empty. Also look in the accumulator sight glass, you may have to put a drop of water in there to clear up the sight glass... if it is bubbling, you are low on freon... dry and oily is empty... clear is plenty of freon.
Then I would check the heater control valve... that big thing you have... find which one of the hose come from water pump... clamp it shut... if heat subsides, then yep, it is that logic board fried.
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