Air conditioner

Welcome to 2CarPros.

When you say fan, are you referring to the engine cooling fan or the interior fan? Also, what are the pressure readings and outside temperatures when checking?

Let me know.

Joe

Engine cooling fan. 75 degrees, A/C on full blast, all the doors open. 40 psi on the gauge and would drop to 20 when fan engaged. When fan disengaged pressure rose back to 40. I had a can of charge with a gauge. The instructions said if it was reading in the green it did not need charging. I added a little and it only dropped 10 psi while fan was on and going to 45 off. I was worried about overcharging the system.

Did you check high side pressure? And yes, I understand your concern, however, at 75 degrees, 40 is normal and when the system engages (fan turns on) the pressure will drop to around 25, so you are a slight bit lower, but it should be working. The only way to know for sure if the system is working properly is to check pressures on both the low and high sides. With the system off, both should be around the same. When engaged, then you should see readings around 20 to 25 on low side and near 200 on the high. (based on between 70 and 80 degrees)

With that, I need you to rent or borrow an AC manifold gauge set from a parts store or if you have one, great.

Connect both sides, low and hi and watch how the pressures change between it being engaged and not (off and on). Let me know both pressures in both conditions.

Since the compressor is working, that tells me there is enough Freon in the system for it to function. If it gets too low, it won't engage.

The following link explains how the AC manifold gauges work and how to check.

Let me know the results.

Joe

The cooling system fan not the A/C fan. It’s at 40 psi then drops to around 20 when fan kicks on.

When the cooling fan kicks on, that usually indicates the compressor has been engaged. Is that what is happening? Expect the pressure to drop when the compressor engages.