'97 E 320 AC question

I have a 1997 E 320 with approx. 86,000 on the clock that's in great shape overall. The air conditioning blows cool at best when you're cruising on the highway, but gets pretty feeble when you get stuck up
in traffic, and we live around NYC. Needless to say, I'd love to get it so it blows ice while idling, so any suggestions would be much appreciated.
I purchased a R134a home recharging kit, and after attaching it to the low pressure valve (to the right of the plenam) with the system running it's reading around 40 psi. According to the idiots guide with the kit that is way too high (in the red!) I know that MB do things as differently as possible whenever they can, so is it possible that my low pressure side is actually too low? When I goose the engine, the guage drops a little bit, but never into the 25 psi range where this kit says that it should be.
I guess a follow up question would be, should I bleed r134a out if this is truly too high?
Also, the car was still hot after running around town when I did this, and the outside temp was around 85 degrees fahrenheit.
Thanks for any help,
J
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wrote:

does your car have access to onboard diagnostics such as described here:
http://www.eclassbenz.com/node/27
if so, run the tests to see if it helps guide you to problem area
http://www.eclassbenz.com/acdiag
also....
http://continentalimports.com /
head to "Magazine Articles" for good info about A/C
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Wow... that's great information. I should browse that whole site to learn more.
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On Jul 13, 3:14 pm, snipped-for-privacy@gmail.com wrote:

Do you know if the code #7, which measures refrigerant pressure, is measuring the low or high pressure side of the system? Is the number in PSI or bar?
Thanks,
J
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