Ac pressure question. Pressure still low?

[ChaseRoads]

Alright. Replaced the compressor, lines and dryer. Pulled a vac for 2+ hours. Let stand for another hour , vac held.

Put 2 12oz cans in, pressure would read like 50 or 60 on the low side when the cam was connected, disconnected the can, and pressure was dropping down to like 20. Ac was blowing cold, orifice tube looked like it would frost over. I was expecting to see closer to 30 psi . Wasn’t sure if this was because of needing more r134a or because the ambient temp is like 45 right now.

 

[Mustang5L5]

45 is a bit too low to really charge. I would wait til at least 60F to charge.

You also want a set of manifold guages so you can read both the high and low side pressures with the system running.

Given that it’s 45 out, I would expect to see the pressures on the low side of things.

 

[ChaseRoads]

45 is a bit too low to really charge. I would wait til at least 60F to charge.

You also want a set of manifold guages so you can read both the high and low side pressures with the system running.

Given that it’s 45 out, I would expect to see the pressures on the low side of things.

I have a set of gauges, I just didn’t note where the high pressure was at. It was on the lower side for sure.

Think it’s best to just leave it be until a warm day? It’ll be awhile before I need the ac, I just wanted the job done and over with.

 

[Mustang5L5]

I would wait. There is risk of damage to the compressor when charging at low temps as you may push liquid through the compressor.


Wait until over 60f…ideally 80s. Charge and note the high and low side pressure and ambient conditions.


Also, when you test pressures you should do it with the system under stress. 80* day, doors open and windows down, fan on high. Hold 1500 rpm and give the system 90 seconds to stabilize. Then record your pressures. High side should be 2.2-2.7 times ambient as a rough rule of thumb. Note both the high and low side pressure.

 

[ChaseRoads]

Got it!! I’ll post back when the temp breaks. I’m just happy it didn’t leak lol.

 

[ChaseRoads]

No huge updates , it was in the 70’s today. Pressure would stay at about 18-20psi at idle. I’m gonna leave it be till it warms up.

Is there a set process to set the pressure on the low pressure switch? I figure I can take a reading and adjust it untill it kicks off at idle then bump it down. Or maybe put a meter on it and wait for it to open up? Or would it be difficult to connect the low pressure switch to my air compressor, set it to 18 psi and adjust the switch till it opens?

 

[Mustang5L5]

I usually watch the guages and see what point the compressor shuts off. Watch a few cycles and then make an adjustment. I shoot for 20-23psi.

 

[ChaseRoads]

I’ve not had a chance to toss the gauges on yet, but it’s 90 out and still blowing cold. Felt silly having the top down and the ac on cold though.

 

[General karthief]

Ain't no more silly than to ride with the top down and the heater on in the winter.
I've done both