Vacuum down after A/C leaks out?

Nope. There's no point to that. Do the repairs, then pull the vacuum for a good 30 minutes or so before adding the refrigerant. At a near perfect vacuum, water boils at 77 degrees. That allows it to be sucked out as a vapor. Moisture in the system promotes corrosion of metal parts, and it can freeze and block the expansion tube / valve / orifice tube / etc. When that happens, cooling stops until that droplet melts and circulates around again.

As a point of interest, when you stop the vacuum pump, wait a few minutes and see if the vacuum holds or begins to decrease. If it decreases, there is either water in the system that is still turning to a vapor, or there's a physical leak yet. Pump it another 30 minutes, then watch it again. If the vacuum holds now, there was still a little water in the system.

Thanks. So did the repair. If I pull a vacuum and it hits -30 but when shut off it drops to 27-28 but holds does this indicate a leak or is some loss normal. Fyi it's 95°+ here.

A little drop is normal. If the vacuum holds for a good 15 - 20 minutes, it's safe to assume there's no water left in the system. There still can be a leak, but it's rather unlikely. Gaskets hold vacuum and pressure. It's when there's a rubber lip seal that it can leak under pressure, but not vacuum, or the other way around. The pressures expected to be encountered are taken into account when those parts are designed, but it points out why there can sometimes be a leak only after the refrigerant is added.

Okay thanks. So, add just a little freon and see if it leaks or should I mostly fill the system?

You can add a little and use a leak detector to be safe but usually when it holds for 20 minutes you should be okay.

Here is a video to help you as well:

https://www.youtube.com/watch?v=4EqdrBVb0sY

Please go over this guide and get back to us.

So it was an expansion valve. I didn't want to overtighten so that or bad seal. Either way I got it fixed, and the A/C is blowing colder than ever.

One question it calls for 29oz of r134 but I only put 24oz in not wanting to put to much in as didn't have a scale. The gauge for the r134 had it at 40 said full between 30-50 well that was the green zone. I know those aren't completely accurate especially at temps over 100°. Should I put a little bit more r134 in the system or is 5oz short ok? Thanks

Nope, if it is cold and working okay I would leave it. Nice work getting it fixed :)

Cool seriously couldn't have done it without your help.

You are welcome, please use 2CarPros anytime we are here for ya.

You have been my go-to for about 2 years now. Made a few donations because you saved me a bunch of money. Cars wouldn't have gotten done probably. This A/C alone quoted $2,700 got it done for less than $500 and that's rebuying r134 because didn't properly tighten bolts.

Happy to hear you solved it. To address the comment about the amount of refrigerant. I too would leave it alone. At the exact proper charge, the lower half of the evaporator in the dash will have liquid and the upper half will be vapor. The point at which it turns from liquid to vapor is where it gets real cold. With too much refrigerant, the evaporator will be overfull with liquid, then it changes state too close to the pipe leading back out to the compressor. The "cold" will be developed under the hood instead of in the heater box. With even more overcharge, liquid can slosh into the compressor and destroy the valves or at least lock it up.

With too little refrigerant, as you may have now, the liquid level in the evaporator will be too low, but as long as there is some liquid, that is still where it's going to get cold. At worst, due to normal leakage over time, you might lose cooling efficiency in, lets say five years instead of six. As long as it's working fine now, there's little point in starting a new can.

Be aware too, if you pop a cooking thermometer in one of the vents, the lowest temperature you should see is around 40 degrees F. The goal of AC systems is to lower the air temperature only 20 degrees. The comfort comes from removing the humidity. And let's face it; 40 degrees is not comfortable. Systems are regulated, either with a pressure sensor, or a temperature sensor to go no lower than 40 degrees. The reason is that humidity condenses on the evaporator, then drips into a pan, then out onto the ground. If the evaporator gets to 32 degrees, that water freezes into ice that blocks air flow. Temperature sensors are usually placed right in the middle of the evaporator, but if there's too much refrigerant, the coldest area of the evaporator will be higher than the sensor. Some freeze-up can still occur.

Awesome thanks. So as long as it's in the green or "acceptable level" that is fine.

Yep, have a great 4th!

Happy fourth.