GMC Repair: A/C PRESSURE CHECK AND FILLING, c lines, 2004 gmc 2500hd

Question
I HAVE A 2004 GMC 2500HD SIERRA. I HAVE A R-134 REFILL KIT, BUT I CAN'T SEEM TO FIND THE FILL PORT ON THE A/C LINES. IT SHOULD BE THE LARGER LINE, BUT THERE IS NOT A FITTING THERE. THERE ARE TWO PORTS ON THE HIGH PRESSURE SIDE THOUGH BUT THE REFILL KIT DOES NOT FIT THOSE. CAN YOU HELP PLEASE? THANK YOU VERY MUCH!!!

Answer
Hi
The one CLOSER to the firewall is the low side. It is smaller diameter fitting than the high side. The valve in the kit SHOULD fit that one.
IF NOT, I would not mess around with it, I would take it to a repair shop and have them put freon into your system.
Good luck
Pawl