A/C Air Temps

[MikeL]

84 300 CD..just had it fully charged w/3 lbs of R12 (in combination w/new drier/compressor/aux fan/expansion valve). I expected the temp of the chilled air to improve substantially over a partially charged system. I was wrong...it takes a long time (20 minutes on highway) to get the cabin cooled down and that's on full blast. It never gets cold enough to have to turn down the fan. What areas should I investigate? Is there a recirculation feature and if so how is it controlled, etc. I was even thinking of bypassing the heater feed hoses to make sure there wasn't any type of accidental heating going on...

Thanks in advance....

[jeffsr]

Three pounds of r-12 sounds a bit high. Make sure that's the correct charge. Overcharging will create a high pressure situation which will produce rapid cycling or no cycling of the compressor, which will severely impair the cooling capacity of the system.

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Jeff Lawrence
1987 300e
1989 300e
1987 BMW 325

[TCCBass]

Mike, I'm glad you posted this...I'm having the same problem. Had the system charged, but the guy didn't use a guage. Seemed like he did put a lot in, but the little window never did clear up. Now, when I am accelerating, the air isn't as cool as when I am coasting. Also, after it was charged, the AC eats up MAJOR horsepower and MPG's. 27 without AC, about 20 with. Maybe it's overcharged?
Thanks for your post.

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R Talley
84 300D-T

[jgl1]

The maximum freon (R-12) charge on the 123 was 2.6 lbs. The factory put a underhood sticker on these vehicles detailing the charge limits for 126, 123 & 107 vehicles; the sticker should be on the cross member above the right headlamp assembly.

Freon overcharge will definitely affect system performance, as well as shorten compressor life (the W124 compressors are particularly sensitive to overcharge).

Another nightmare you may have to endure: how much refrigerant oil was added to the system during repairs? The Delco R-4 compressor circulates its oil throughout the system, as it has no sump. If the system is oil-logged, cooling will be adversely affected.

What was the reason for the compressor renewal? Was it worn or had it seized?
If it had seized, then the entire should have been thoroughly flushed and the suction manifold assembly replaced [in the 1980s M-B came out with a service advisory stating that in the event of compressor seizure, metal particles were ejected into the system;
flushing was incapable of removing all of these particles and hose renewal was thus mandated].

[MikeL]

My compressor was seeping R12 (and was a little noisy) and with the cost and aggravation of recharging, it made more sense (to me at least) to just fix the entire 15 year old system correctly and be done with it...The oil charge was 10oz. The compressor appears to cycle correctly (vs a frequent on/off from high pressure).

[stevebfl]

If you have any compressor left, I would say that overcharging and over oiling was definitely the problem.

10 onces of oil is too much for a virgin sytem dry. Unless you went to heroic messures you probably have half of the original 6-8 onces that it came with giving you a total of 13-14 onces in a system designed for 6-8 in memory serves me.

[Mike Murrell]

And an add on to Steve's post.....

If you have too much oil, you're likely to destroy the new/renewed compressor. A/C compressors are designed to compress gas; not liquid. The unit may be compressing a mixture that is more liquid-like than it was designed to compress. My 2 cents.

Mike Murrell
'91 300-SEL