Aerius

So I was driving my ML55 AMG and the A/C was blowing cold air as normal( I live in the Caribbean so its kinda a must) when suddenly it started blowing hot air on the coldest setting. After a bit of googling and troubleshooting. The coolant level was below the cold level, both the high and low pressure AC lines were hot and the clutch on the compressor was engaging normally whenever I turned the A/C on.

I was going to get some coolant but knowing the car was a mercedes I'd expect something special and did a bunch of googling and came upon the mercedes product specifications website with the approved coolants. I know already that it needs a 50/50 mixture of antifreeze/anti-corrosion to water but what coolant products would you guys suggest. i haven't bought any yet. Also I forgot to add that the engine was getting hotter than usual(the low coolant level is the suspect).

The A/C compressor is new as it was installed in a recent service. So do you think the low coolant level is the suspect? or is it low on freon( unlikely but what do I know). If so where is the low pressure line located. I also heard touching the dryer to see if its cold helps troubleshoot but where is that?

vvrjrlaw

I believe you may have an HVAC actuator issue. Although they generally don't go bad while in use. Either way if the compressor is engaging and you're getting just hot air the actuator door is not closing off the heat and permitting the cold air to enter the cabin.

Aerius

Is there a tutorial on how I could get access to this actuator? possibly to see if it has actually gone bad? Or is it just guess work on whether it's working or not.
Regardless how do I gain access to it

vvrjrlaw

Yes but not on this forum. Google is your friend, use it.

Aerius

ok so I don't think its the blend door motor(HVAC actuator) cause if I set the knob its gets hotter, alot hotter. If i switch the knob back to fully cold I hear vents opening and cool/warm air blows in. So from what I can tell the actuator is fine but I could be wrong.

I touched both the pressure lines on the fire-wall on the passenger side shown here


and one is hot while the other is warm, what does that show? low refigerant? bad compressor(even though clutch engages and it was recently replaced)? or could it still be the blend door motor