I just bought a recharge kit, complete with R-134A, hose and guage. The only problem I'm having is locating the low pressure service port. Can anyone direct me to the correct port? Or the vicinity I should be looking?

TIA

on the pass side of the engine bay, the low side line comes off the compressor, and the service port is sticking right out in plain view.

And the fitting won't work attach to the high pressure side. It's a different size.

the low and high side fittings are different sizes so you can't mix them up.

Yeah, I found the correct fitting. But when I attached the guage it went into the red. From the instructions it should only indicate green (good) or yellow (low). Red indicated a problem.

was the A/C running? when the car or compressor is off, the high and low side pressures will equalize. then when the compressor kicks on, the high side should raise, and the low side will drop.

was the A/C running? when the car or compressor is off, the high and low side pressures will equalize. then when the compressor kicks on, the high side should raise, and the low side will drop.

Well here is what I did, I attached the hose while connected to the can of R-134A (unopened) to get an initial reading, which was in the red zone. Then I turned on the a/c at full blast and set the temp to 60. I let it run for a few minutes and the reading stayed in the red. The a/c was fine last summer, no problems, cold. Now it blows warm, when I hit the a/c button, I can feel the idle change a little so I assume the compressor is kicking in. Could I be doing something wrong? The kit cost about 30 bucks, to take it to the shop would coust 100 more so I wanna see if I could solve this on my own first. The manual says I should let the a/c run for 2-3 minutes and then take another reading, the car was already at operating temp also. Any ideas?

If memory serves, the charge procedure for an E39 (or other modern BMW) is a matter of slightly overcharging the system and then removing refrigerant until certain temps internal to the system are reached. This does require the services of a proper diag system that can display live data from the A/C system.