I have a gauge to read the high side pressure on my 1998 leSabre. The prong in the middle won't open the Schrader valve down inside the R134 connection. ID tech said the prong may be slightly too long? The outer part of the connect snaps down onto the high port just like the low port connector does IF I remove the prong in the middle of the adapter-it just unscrews.

Has anyone had a problem with the valve in the High side being hard to open?

I've added a few ounces of freon to bring up the low side pressure to the top of the 25-45 optimal setting. The system had gotten warm on high temp days (90s and up) unless the car was moving down the road.

I'd like to know what the high side pressres are to match with the chart in the factory service manual.

I don't think you can pull the high side the way you want w/o discharging the freon first. Have you considered tying a different gauge?