Starting fresh with A/C system. Pressures too high - PeachParts Mercedes-Benz Forum

Diseasel300 · #15 08-17-2017, 08:40 PM

Quote:

Originally Posted by ps2cho

This is the problem I have when I post this issue online, everybody just reads the pressure, but does not read that I am UNDERCHARGED. I need someone who has more experience to tell me whether an overcharge of oil will provide excess pressures. That is all! If excess oil will not do this, then I can look elsewhere!

Have you bothered to deal with airflow across the condenser? If not, your pressures are arbitrary and meaningless. The system pressures will continue to vary with load and with the amount of refrigerant in the system. Even if you keep adding refrigerant, the head pressure isn't likely to rise very quickly as the liquid begins to fill the condenser.

Charge by weight (80% of the R12 weight) and THEN check pressures with a fan blowing across the condenser. At 105˚ and a high load on the system, your pressures will be high. My SDL runs ~350-360/55-60 at the same temps with the fan on high and all 4 windows down. Once the cabin pulls down to temp, the pressures drop dramatically, more along the lines of 250-275/30-35.

Load and airflow matter when measuring pressure. This is why you charge by weight.