Where is the airconditioner recharge port on a 2008 Pontiac Montana Van

IN FRONT OF THE RADIATOR TOWARDS FRONT BUMPER. YOU WILL NEED A LONGER HOSE 18 -24 INCHES AS IT IS HALF WAY DOWN THE RADIATOR, BE CAREFUL AS ITS TIGHT AND MOVING PARTS.

Sounds like the anti-theft/alarm system was triggered.
Have you tried locking and unlocking the driver door with the key to disable the alarm ?
And you need at least 12 volts to crank the engine so the battery may need to be charged up first.

find your reset switch and reset it

You may just have to have the system recharged with coolant. When was the last time it was checked?

the low pressure port is ALWAYS between the firewall and the compressor, on ANY car. so its there.

google blue book for your car and you should be able to find out.

Yes the A/C condensate drain is probably cloged up. I have not worked on a Montana but if you look at another GM mini van with the A/C on and the condensation driping out the bottom you can see where the drip comes from.
I hope this helps you.

Bad News. I recently had the same type of smell ( no leaks or puddles either) coming from my van and had to have the intake manifold gasket replaced due to the Dex-cool issue. It appears GM installed an inadequate/substandard gasket when they built the van. My van only had 65,000 miles on it. There's a Dex-cool settlement you could have applied for but repairs had to be made by May of 2008.

This is the only real complaint I've had with the van.

The ecu is located under the Air filter housing on my 99 montana

the low port is between the engine and the radiator support and the high pressure port is by the cruise controll module