Thoughts on my r134a pressure?

[JerseyJoe]

Before I evacuate the system and start fresh, can anyone comment on my compressor seeming to cycle on and off so much?
Vintage Air recommends 6-18 psi steady. https://www.vintageair.com/tech-topic-troubleshoot-system/#:~:text=Acceptable operating pressure ranges for,PSI in a steady state.

Here's a vid of my system at about 15 psi when the compressor is running, high side was within range at around 200 psi in 90 degree heat. Center vent temp has me thinking air in the system... Thanks in advance

 

[Beekeeper]

What’s the high side pressure look like when your compressor is running?
I think your system is under charged. At 90 degrees ambient your low side should be 45 to 55 psi high side 250-270 when the pump is running at least that my experience with 134A

 

[JerseyJoe]

What’s the high side pressure look like when your compressor is running?
I think your system is under charged. At 90 degrees ambient your low side should be 45 to 55 psi high side 250-270 when the pump is running at least that my experience with 134A

Those numbers sound more like what I've seen with 134a. But I'm a novice... Not sure if I'm misreading the Vintage instructions. I'll hook up the vac in the morning and report back. Gonna make sure all of the connections and grounds are good, too. Thanks BeeKeeper

 

[Cranky]

What's the temp of the air coming out of the register?

 

[bearman]

Couple of questions do you have a low and high pressure switch on the system
Is the condenser fan on
If you rev it up does it stay cut out. Or does it still cycle.
But my first thought is low on freon like stated above.

 

[JerseyJoe]

What's the temp of the air coming out of the register?

60 degrees. Definitely not cool cruising!

 

[JerseyJoe]

Couple of questions do you have a low and high pressure switch on the system
Is the condenser fan on
If you rev it up does it stay cut out. Or does it still cycle.
But my first thought is low on freon like stated above.

It's a binary switch that came with the kit. Fan is running, revving and regular driving it still turns compressor on and off frequently. I'm going to evac and recharge in the morning. I appreciate the replies, I'm just second guessing my diagnosis. Thanks

 

[Cranky]

Does this system make any mention of how many oz it should have for the intended vehicle? If you are using 12 oz cans to fill, figure in that you are going to lose at least 2 oz per can through the hoses and gauges and since the system won't really pull much once the can is almost empty, there will also be about an oz still left over in the can.

 

[JerseyJoe]

Does this system make any mention of how many oz it should have for the intended vehicle? If you are using 12 oz cans to fill, figure in that you are going to lose at least 2 oz per can through the hoses and gauges and since the system won't really pull much once the can is almost empty, there will also be about an oz still left over in the can.

Vintage says 1 lb. 12 oz. I am using small cans, but I use a small digital scale as well as watch the pressure. I'll be shooting for the 45-55 lbs. mentioned above and see if the compressor stays on.

 

[Roger63]

I agree with some of the other answers, depending on the capacity of the system. High side pressure should be 220 to 250 psi with a smaller capacity system being the higher range.

 

[bearman]

Is the low side hose hot or cold
If there was air in the system the gauges would be bouncing (needles)
When you evac and then hook up the hoses to fill you did purge the hose correct

 

[JerseyJoe]

Is the low side hose hot or cold
If there was air in the system the gauges would be bouncing (needles)
When you evac and then hook up the hoses to fill you did purge the hose correct

Low side was "slightly cool" as it was sweating just a little bit. I do always purge the hoses.

 

[bearman]

Either low on freon or pressure switch screwed up.

 

[1 Wild R/T]

Vintage Air needs to educate their phone "tech"

 

[Demonic]

You are under-charged.

You did pull a vacuum first, right? I usually aim for a 36 to 38* evaporator, just off idle.

 

[JerseyJoe]

You are under-charged.

You did pull a vacuum first, right? I usually aim for a 36 to 38* evaporator, just off idle.

Yes, for about an hour, then close up the valves and watch for a leak.

 

[Beekeeper]

Yes, for about an hour, then close up the valves and watch for a leak.

if you pulled vacuum for and hour and there’s no leaks in your system there’s no atmosphere in there. Just top off the refrigerant to the expected pressures from the temp chart and roll with it.

 

[1 Wild R/T]

You don’t charge to a certain pressure, you charge to subcooling. And check operation of expansion valve by superheat. Discharge air temp will vary depending on ambient air temp., humidity and fan speed.
Your pressures are low. If you weighed it in to manufacture specs then you likely have a restriction. (Dirt, moisture, bad txv...). More information is needed to determine.
If you have a restriction, adding more refrigerant will cause more problems.

You had to complicate this... Automotive A/C has been charged using pressures since the dawn of time...
With aftermarket A/C they don't print a spec for how much refrigerant because hose length varies...

If he had a restriction the high side would be low but the low side would be high... Both sides low tends to indicate under charged... Which is exactly what he's been told... If he adds R134 & it doesn't work we'll deal with it but I'm betting it'll be fine...

 

[Beekeeper]

Yup you can’t charge 134A in an auto anything like you do in a fixed unit that doesn’t roll down the road at different speeds. So yes charge to the temp chart and roll on.

 

[Beekeeper]

Yes you can.

well yea you could as long as you don’t plan to drive it anywhere and just sit and idle it. Otherwise seems like a waste of time to me.