Pressures for air conditioning on 1991 Chevy lumina
At 75° ambient temperature low side 35-45psi, high side 120-140psi. The hotter the ambient air, the higher the pressures will (should) be. Your Lumina was manufactured with R12 Freon, and is not for sale to the public.
Has it been retroed to 134A?
I would suggest low side at 30-35 psi and high side 150- 160 psi. But the pressures are relative to outside temp, condenser fan operation, and engine speed. The pressures I noted would be on a warm day, condenser fan on, and engine at 1200-1500 rpm.
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