We are roasting alive here in North Arkansas. Tomorrow I'm going to try to fix the AC on my '85 300TD. My dumb question: Which button turns on the compressor? Let's number them 1 to 5. I know what 1 and 5 do, but what about the middle three? No owners manual came with this car!! Thanks....

I'll assume 1 is on the left and 5 is on the right:

1 is for the defroster and blows hot air out the vents at the windshield and the vents that you can aim at the passenger windows.

2 Blows cold air (if your A/C is working) out of the upper and lower vents. (Up and down white arrows.)

3 Blows cold air out of the upper vents only. (White up arrow and empty down arrow.)

4 has the letters EC on it and blows outside air into the cabin. EC stands for "economy".

5 has a circle on it and turns the whole system off.

So, to answer your question, 2 or 3 will turn on the compressor if everything is working properly.

Good luck. Hopefully in a few weeks the heat will mitigate and you won't need the A/C. I hope so.

Richard

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1, defrost, engages the compressor and heater on full.

2 and 3 engage the compressor if the cabin temp sensor says the cabin is warmer than the thumbwheel setpoint. That's a simplification of it, anyway.

4 and 5 will not engage the compressor regardless of cabin temperature.

Sixto
87 300D

Thanks for fine tuning my response. I did not know that about 1 and regarding 2 and 3, assumed the wheel would be set low enough to trigger the A/C. That is a good clarification.

__________________
85 300D 75K Anthracite Grey 0-60 in 13 seconds **For Sale**
84 300D 333K Black (The Velveteen Rabbit) 0-60 in 14 seconds
00 Toyota Sienna 208K (Sold)
15 Subaru Outback 43K
11 Subaru Outback 67K
98 Ford Taurus 100K (Gertie - Was Grandma's - drove it to church and shopping - really) Daughter's car now.
30 Model A Ford 2 Door Sedan (Sold) 0-60 in . . . Never reached 60

It's actually simpler than that. 2 and 3 engage the compressor. Period. If the requested temp is higher than the cabin temp, the heater is used to warm things up.

The ACC does not regulate temp via the a/c. The only "trigger" that is needed to engage the compressor clutch is push button 1, 2 or 3. The only thing that will (normally) disengage the compressor is the evaporator temp dropping below 36 degrees F.