Automatic climate control function - Mercedes-Benz Forum
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post #1 of 23 (permalink) Old 04-20-2019, 10:33 AM Thread Starter
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Automatic climate control function

Hi i'm wondering how the acc in my car works imagine this scenario:

outside temp 80 I set my temp at 70 middle button pressed low fan speed

what will the system do:

A. cool the evaporator just enough to keep the interior at 70 without using the heater and to save the compressor and increase gas mileage

or

B. cool the evaporator down to freezing and also use the heater to bring temp up
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post #2 of 23 (permalink) Old 04-20-2019, 01:27 PM
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I don't know the answer to this but I suspect it can be found in section 83-600 of the manual. It goes into quite a bit of detail.
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post #3 of 23 (permalink) Old 04-21-2019, 08:53 AM
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just set fan on auto and leave it alone. adjust temp dial in very small increments to compensate for various temp changes.

I think A is what happens.

I tell my wife all the time that setting the thermostat on the lowest setting doesnt make the car cool off faster. (After giving up on that conversation I finally got her to change because her CLS550 eco start/stop wont work if the interior temp is different that the thermostat setting.) The compressor is either on or off depending on demand.
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post #4 of 23 (permalink) Old 04-21-2019, 10:46 AM Thread Starter
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I think the answer is B

the 83-600 section of the manual for the middle button (button c) says this:

"The compressor is added, the evaporator temperature is held to approx. 0 C"

and this:

"The refrigerant compressor of the air conditioning system is switched on at outside temperatures above +4 C"

also if you read section 83-601 (function test) with button c compressor runs on every temp setting.

Test 6 shows button c and temp wheel at 22 C and both compressor and monovalve are switched on so I think the answer to my original question is B.


So the system in my 300SE is less efficient than in my old 240D which had manual climate control and had a separate rotary wheel for the air conditioner strenth setting while the heater had its own two rotary switches (left and right side) and it was just a simple linkage from the dash to the heater valve.
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post #5 of 23 (permalink) Old 06-15-2019, 11:44 AM
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A and B is wrong. 1. With the a/c on, heater control valve shuts off the hot water flow going into the cab. 2. The a/c system has a temp sensor that turns off the compressor when temp gets below your deg setting and turn on when gets above the deg setting. 3. The a/c system cycles the compressor off and on to your settings. 4. If the heater has hot water going thur the water control valve and at the heater/evap core then the temp would never get cold.
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post #6 of 23 (permalink) Old 06-18-2019, 10:00 PM
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In other words, the heater is not used. In short the compressor is controlled to cycle on and off.
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post #7 of 23 (permalink) Old 06-20-2019, 07:35 AM
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Quote:
Originally Posted by rumb View Post
just set fan on auto and leave it alone. adjust temp dial in very small increments to compensate for various temp changes.

I think A is what happens.

I tell my wife all the time that setting the thermostat on the lowest setting doesnt make the car cool off faster. (After giving up on that conversation I finally got her to change because her CLS550 eco start/stop wont work if the interior temp is different that the thermostat setting.) The compressor is either on or off depending on demand.
Hey rumb!

My CL550 doesn't do that I don't think?

Current Stable:
2012 CL550 C4 4MATIC Coupe


Past cars:
1991-560 SEC AMG - Coupe - 199/261 - 300 HP Custom Built Motor - Highly Modified Coupe.
1990-560 SEL - Sedan - 199/261 - Stock. Euro Headlamps & Wipers
1987 560 SEC Black/Tan
1988 420 SEL Champagne/Brown



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post #8 of 23 (permalink) Old 06-20-2019, 07:36 AM
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Originally Posted by zpa001 View Post
In other words, the heater is not used. In short the compressor is controlled to cycle on and off.
+1 - The heater is NOT used. The compressor IS cycled.

Current Stable:
2012 CL550 C4 4MATIC Coupe


Past cars:
1991-560 SEC AMG - Coupe - 199/261 - 300 HP Custom Built Motor - Highly Modified Coupe.
1990-560 SEL - Sedan - 199/261 - Stock. Euro Headlamps & Wipers
1987 560 SEC Black/Tan
1988 420 SEL Champagne/Brown



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post #9 of 23 (permalink) Old 06-20-2019, 07:37 AM
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Quote:
Originally Posted by zpa001 View Post
A and B is wrong. 1. With the a/c on, heater control valve shuts off the hot water flow going into the cab. 2. The a/c system has a temp sensor that turns off the compressor when temp gets below your deg setting and turn on when gets above the deg setting. 3. The a/c system cycles the compressor off and on to your settings. 4. If the heater has hot water going thur the water control valve and at the heater/evap core then the temp would never get cold.
This is correct.

Current Stable:
2012 CL550 C4 4MATIC Coupe


Past cars:
1991-560 SEC AMG - Coupe - 199/261 - 300 HP Custom Built Motor - Highly Modified Coupe.
1990-560 SEL - Sedan - 199/261 - Stock. Euro Headlamps & Wipers
1987 560 SEC Black/Tan
1988 420 SEL Champagne/Brown



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post #10 of 23 (permalink) Old 06-20-2019, 08:24 AM Thread Starter
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if you read section 83-601 (function test) with button c (middle one).

Test 6 shows button c and temp wheel at 22 C and both compressor and monovalve are switched on.
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