A/C Stuck in EC
Thread Starter
Super Member
Joined: Mar 2002
Posts: 664
Likes: 33
From: Ft. Lauderdale
2015 C300, 2025 GLC300 4Matic
A/C Stuck in EC
My A/C is stuck in the EC mode. No matter how many times I push the button, the EC light will not go out. Of course now I have no cooling. Any Ideas?
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Joined: Oct 2007
Posts: 1,564
Likes: 19
From: SoCal
98 Brilliant Silver E320 Wagon
DIY: Climate Control Diagnostics
How to run built-in Climate Control Diagnostics.
1 - Start engine
2 - Turn on Climate Control and adjust to 72F (22C) on both sides. This is done easily by holding UP and DOWN arrows simultaneously.
3 - Wait 3 - 5 min unless engine is already up to temp.
4 - Press and hold the REST button for at least 5 seconds and release when the left side of the display shows an '01'
5 - Record the left and right values on a piece of paper.
6 - Press the 'AUTO' button. The value '02' should appear on the left.
7 - Repeat while recording the value on the left and on the right.
8 - Some values on left will not be consecutive. Some will be missing. Just write down the ones you get.
9 - When you get to '24' press REST to exit.
Here is what the values mean. [Note: Some temp values may be in C instead of F.]
01 Inside (cabin) temp
02 Outside temp
03 Left heater core temp
04 Right heater core temp
05 Evaporator temp
06 Engine coolant temp
07 A/C Compressor pressure (bar)
08 Refrigerant temp
21 Engine rpm (x100)
22 Vehicle speed (mph)
24 Battery voltage
Most common problem with EC light staying on is low refrigerant. Low refrigerant will result in compressor not starting and compressor pressure (07) will be zero. At one time an older style Refrigerant Temperature Sensor was subject to moisture build up and that would cause the EC light to stay on. All newer models have an improved RTC design.
Here is a test run from my car.
01 27
02 23
03 06
04 07
05 05
06 51
07 12
08 39
21 07
23 00
24 13.5
Hope this helps some.
1 - Start engine
2 - Turn on Climate Control and adjust to 72F (22C) on both sides. This is done easily by holding UP and DOWN arrows simultaneously.
3 - Wait 3 - 5 min unless engine is already up to temp.
4 - Press and hold the REST button for at least 5 seconds and release when the left side of the display shows an '01'
5 - Record the left and right values on a piece of paper.
6 - Press the 'AUTO' button. The value '02' should appear on the left.
7 - Repeat while recording the value on the left and on the right.
8 - Some values on left will not be consecutive. Some will be missing. Just write down the ones you get.
9 - When you get to '24' press REST to exit.
Here is what the values mean. [Note: Some temp values may be in C instead of F.]
01 Inside (cabin) temp
02 Outside temp
03 Left heater core temp
04 Right heater core temp
05 Evaporator temp
06 Engine coolant temp
07 A/C Compressor pressure (bar)
08 Refrigerant temp
21 Engine rpm (x100)
22 Vehicle speed (mph)
24 Battery voltage
Most common problem with EC light staying on is low refrigerant. Low refrigerant will result in compressor not starting and compressor pressure (07) will be zero. At one time an older style Refrigerant Temperature Sensor was subject to moisture build up and that would cause the EC light to stay on. All newer models have an improved RTC design.
Here is a test run from my car.
01 27
02 23
03 06
04 07
05 05
06 51
07 12
08 39
21 07
23 00
24 13.5
Hope this helps some.
