My van cools okay when going down the road, but does not cool at all
when at an idle. I've hooked up pressure gages and they read about 40
psi on the low side and 200 psi on the high at idle and at 2000 RPM
they read 30 psi and 230 psi. The outside temp is about 90F with about
50% humidity. I'm thinking I just need to add a little refrigerant,
but don't want to overcharge a system that has a different problem.