How do you replace the refrigerant on a 1990 Chevy s-10 pick up?

Answer 1

I don't truly understand what you are asking but if the a/c system is cooling you don't need to replace the freon...

If you are trying to evacuate and recharge the a/c system then you will need to do the following..

1. Take the truck to any auto a/c shop and have them reclaim the freon..

2. Using a set of a/c gauges put the red hose on the high side and the blue hose on the low side then put the yellow hose on your vacuum pump..

3. Pull a vacuum for around 1-hour and then let it sit for 1-hour.

4. If it holds then add the correct amount of both freon and oil.

5. When finished the low side should be in the area of 35 to 40 psi and the high side should be in the area of 200 to 250 psi..