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Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 28190
Experience:  Over 15 years experience as a Mercedes dealer technician
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S500: air conditioner..push..the ac to come on the red light stays on

Resolved Question:

S500 air conditioner light is red, now when i push it for the ac to come on the red light stays on and no ac
Submitted: 8 years ago.
Category: Mercedes
Expert:  Pete replied 8 years ago.
Hello,is this the ec button that lights up?Thanks Pete
Customer: replied 8 years ago.
ac light button is by the radio on the right, the defrost button is like it but on the left of the radio
Expert:  Pete replied 8 years ago.
o.k.,this is indicating a fault in the ac system,it could be low on freon which causes this light to light up or any other failures could cause this.have you had your freon level checked at all?Thanks Pete
Customer: replied 8 years ago.
If it needs freon would the light go off when freon is put in, Well when I push button?
Expert:  Pete replied 8 years ago.
It may go off but in most cases the code will have to be cleared out of the heater/ac pushbutton controller with a mercedes SDS machine at a dealer n order for the system to operate normally again.This machine can also code this freon system check out of the hvac/ac computer so if the freon were to get low at some point again it wont disable the system and turn this light on.Freon is one of the big items that causes this light to turn on but you may have other faiures that have turned the light on,it may not be the freon,a Mercedes SDS machine at a dealer can read out the fault codes in this sytem to aid in diagnosing the failure,but if it is that the freon level is low then the leak would have to be found and then the ac recharged and the code cleareed out, i hope this helped,if you need anything else let me know,Thanks Pete
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Customer: replied 8 years ago.
This light is always on. Only if i want the ac on do i push it and it go off and the ac works. When it is pushed again the light comes on for me to cut off the ac. this is the usual procedure. It's like the ac button is stuck
Expert:  Pete replied 8 years ago.
it may be the controller has failed but this could be the warning light on this sytem to let the driver know that there is a fault in the system(usually its the EC button that lights up and wont turn off when there is a fault but if your system doenst have the ec button then this ac button may be the indicator when it stays lit like it is now to let you know ther is a fault in the system)If you can locate the fuses for the ac/heater controller you may be able to remove them for about 2 minutes then reinstall them to reset the system to see if it operates ok then.If it doesnt then it would have top be taken in to see what the fault is whether its the ac controller or if it is just low on freon.Thanks Pete