What does too much pressure on the low side of the air conditioner in a 1970 monte carlo 350 mean

If you are sure your gauges are reading correctly it could be the compressor going bad. Double check your gauges though before thinking the worst. Have seen these gauges not read correctly. Might want to try a different set just to be sure.

In 1970, it has since been changed, the connections for low and high side were the same size and thread nipples. They changed that because people were hooking up Freon re-charge cans on to the high side, pumping IN to the re-charge can and blowing themselves up. Double check that you have your gauge hooked up to the low side. Now days the nipples are different and you can't hook it up backwards Also, please don't vent Freon in to the atmosphere. Not only highly illegal but just plain wrong. Thank You.