Intermittent A/C?
08-11-2020, 11:52 AM
#27
Super Member
@yap: I don't know that you can "check" the fan, unless it's completely stopped spinning. I'm pretty sure these cars use a multi-speed fan and probably have some logic which will try to compensate for specific fan motor windings going bad, at least the VWs do.
As far as why AC systems traditionally cut out- 1) High head pressure. Quite simply the refrigerant gets up to too high of a pressure inside the system and to protect itself, the compressor shuts down, otherwise it'd start breaking vanes on the inside of it. Usually you'll see this on very hot, humid conditions vs. cooler, dry conditions. 2) Evaporator coil is freezing up. Toss a thermometer in the AC vent and see how low it's reading. I'm not sure what normal is on a W212. BUT, if you're seeing 2C or colder out of the vents, good chance this is what is happening. Believe it or not, the evap coil freezing up is usually caused by too little refrigerant, although reduced airflow can also cause it.
Unfortunately, Mercedes has gone waaaay overboard when designing their AC systems, to their detriment. My old Infinitis used primitive HVAC systems, but it was ****-simple to troubleshoot, which was good -- they each liked to eat AC compressors about every 100k miles. Ridiculously cold too. My M45's "broken" AC performed about as well as my W213's fully functional AC. The M45's, when working fully, was sometimes too cold, even for Florida summers. Not a bad thing at all.
As far as why AC systems traditionally cut out- 1) High head pressure. Quite simply the refrigerant gets up to too high of a pressure inside the system and to protect itself, the compressor shuts down, otherwise it'd start breaking vanes on the inside of it. Usually you'll see this on very hot, humid conditions vs. cooler, dry conditions. 2) Evaporator coil is freezing up. Toss a thermometer in the AC vent and see how low it's reading. I'm not sure what normal is on a W212. BUT, if you're seeing 2C or colder out of the vents, good chance this is what is happening. Believe it or not, the evap coil freezing up is usually caused by too little refrigerant, although reduced airflow can also cause it.
Unfortunately, Mercedes has gone waaaay overboard when designing their AC systems, to their detriment. My old Infinitis used primitive HVAC systems, but it was ****-simple to troubleshoot, which was good -- they each liked to eat AC compressors about every 100k miles. Ridiculously cold too. My M45's "broken" AC performed about as well as my W213's fully functional AC. The M45's, when working fully, was sometimes too cold, even for Florida summers. Not a bad thing at all.
08-11-2020, 09:38 PM
#28
Thanks for giving knowledge about the cooling fan.
I checked lower pressure although I don’t have a kit for high pressure valve.
Lower pressure was 37 psi.
I think it’s bit lower but in normal condition.
I have never refilled gas, so it’s not in high pressure, I guess.
Can I refill AC gas?
Center vent temps was 8.5 celsius degree.
Do you guess something else?
I checked lower pressure although I don’t have a kit for high pressure valve.
Lower pressure was 37 psi.
I think it’s bit lower but in normal condition.
I have never refilled gas, so it’s not in high pressure, I guess.
Can I refill AC gas?
Center vent temps was 8.5 celsius degree.
Do you guess something else?
