Bad AC comp or add just freon?

Blowing warm air.

Compressor clutch engages when air turned on. I replaced the clutch coil last summer.

Low side reading ~39 High side ~45. Low side does react (very little) when RPM is increased, high side does not.

Most of my findings lead me to believe that the compressor is bad but I also know that low freon will make my high side low.

Car (98 grand-prix se 3.1) only has 49k miles on it and I feel the compressor should still be good (that’s partly my wallet talking as well).

Should I gamble and try to add freon and see if it improves?

Replacing the comp and related items is just not a financial endeavor I need right now.

You don’t say @ RPM’s the engine is at.

What’s the static pressure reading?

Tester

2500 RPM or so.

I posted the gauge readings.

You want to simulate as if the vehicle is traveling at 60 MPH.

So, the engine RPM’s should at 2,000 with a large fan blowing at the condensor.

Again, what’s the static pressure?

Tester

High side remains the same, in the high 40s

Low side is maybe 5 lbs less at idle.

That’s not the static pressure.

What do the gauges read when the engine isn’t running?

Tester

Well, those are the pressures I have when it’s not running.

See! Now you’re making things confusing.

Take it to a certified AC technician.

Tester

Car off, 30 ish on the low side, 45 ish on the high side.

Car running, the same.

Car rpm increased to 2500 ish, low= 39 high= 45.

Not confusing to me.

The readings on the gauges should be the same without the engine running.

That’s static pressure.

You got bigger problems than low refrigerant.

Tester

You’re saying that the low and high side readings should be precisely the same at idle and with the car off?

With $27 gauges from Amazon AND a perfect system, you most likely won’t see identical numbers on both sides. Not to mention all the other factors.

A static pressure difference of 5-9 lb isn’t an issue.

I’ll add freon and see if it comes up, if not, I’ll know exactly what to do next.

You shouldn’t be messing with AC system since it’s obvious you don’t know what you’re doing or talking about.

Static A/C pressure in a car should be measured when the system is not operating, but it is important to note that the pressure will equalize between high and low sides shortly after the system is turned off. Typical low side pressure can be around 70 psi before the engine is turned on for a recharge.

Tester

I agree with Tester on this, and most any A/C tech will agree also…

For example, your vehicle on a hot day say ambient temperature of 90° with humidity about 75% the engine off static pressure on a 100% working vehicle like yours will be around 110 psi (on both high AND low side psi), when running around1800+rpm with a large fan blowing across the condenser your head (high side) pressure should be ambient temperature times two plus 50 psi, so on a hot day as described above that means the head (high side) pressure should be around 230 psi and low side around 35 psi… The orifice tube or x-valve should allow the pressures (with engine off or A/C turned off) to equalize no matter what it is… With the engine off or at least the A/C compressor turned off, the high and low side WILL be the same…

In your case after checking for leaks, the proper way is to evacuate all the freon out of the system and maybe pull a vacuum and see if it will even hold a vacuum, then add the correct measured amount of freon back in so you know you have the proper amount of freon and then re-check the Head and Low side pressures and go from there, I would also add dye when charging the system to help find the leak…

If the ambient temperature is greater than 45 F, those pressures indicate your system has less than 1 ounce of refrigerant. Add refrigerant, perhaps you can get one more season from this vehicle.

Besides the AC . . . what’s the overall condition of this 1998 Pontiac Grand Prix?

Sorting out an AC system properly can be quite labor intensive and expensive, in my experience

Does this car warrant a proper repair, if it were to cost several hundred dollars . . . or more?