Low Side Pressure Recommendations
 

On my 91 300D, AC was weak due to slow leak and aux fans weren't coming on at all. I didn't have a proper set of gauges (my next purchase), but I did have a charging gun with a low side gauge. Reading was about 37 psi at 80F or so.

The charging gun came with the pressure recommendations at the end of this post. So I added refrigerant until pressure was about 45 (took about 10oz.).

AC is cold, fans are coming on. But my concern is that, by simply using these generic recommendations, I may have overcharged the system (based on what a couple of knowledgeable MB folks have told me).

Thoughts?

Thanks for your continued help as I continue along the learning curve.



Ambient Temp Pressure

65 25-35

70 35-40

75 35-45

80 40-50

85 45-55

90 45-55

95 50-55

100 50-55

105 50-55

110 50-55

I would NEVER recommend charging based solely on low side pressure. Buy, beg, or borrow a manifold gauge set so you're not trying to fight with one arm tied behind your back.

Buying a set this weekend. Do I use pressure recommendations that come with kit, or is there something more specific for my car?

ahh. now I understand, your PM's didn't have all this info.
yes, I'd say you are overcharged. heed the warnings I gave you in the PM's and larry's word is golden.
I think now you need to go to a shop and get some 134 removed from the system.
like I told you in the PM's it's just too difficult to explain all the variables to a DIY without any tools. the slow charging procedure I outlined will get you in the ballpark, but please don't pay attention to the charging chart. showing you low pressures based on outside ambient leaves out a huge amount of info for getting your system right.

I should add that the reading I took was with engine at idle. So low side pressure is less with engine at 1500 rpm or so. As to how much less, I will need to enlist the support of my "assistant" (aka wife). Anyway, perhaps my initial report was skewed high....

FREE Generic A/C training material for beginners:
 

Climate Control:
http://www.peachparts.com/shopforum/showthread.php?t=142408






Have a great day