Ac help (1 Viewer)

[88red]

Ok, I'm stuck on an issue and think it may be a clogged expansion valve but before I jump on that I wanted a second opinion.
I flushed the condenser,lines, evaporator, replaced the pump, receiver/drier, o-rings, and the expansion valve. After evacuating the system when I go to charge on the high side it won't take more than 1/2can and only gets to about 75-80psi. No pressure on the low side. The high side gets enough for the clutch to engage but pressure won't build and still nothing on the low side. The fsm has me thinking that it is a clogged expansion valve but it is new and a royal pain to get to. Any thoughts? Why won't the high pressure side build up even with a clogged valve?

 

[88red]

And is this in the right way?

 

[pandasfj]

Just a thought but is the shrader valve on the low side actually being depressed by your hose? there should be some kind of flow thru the compressor to bring the low side up. drier inlet should be coming from the condenser outlet.

 

[SteveH]

After evacuating the system when I go to charge on the high side it won't take more than 1/2can and only gets to about 75-80psi.

Why are you charging the high side?

 

[ibinazbass]

Pressure will never build with the compressor running if there is no refrigerant on the low side for it to pressurize. I would say its either the expansion valve or the evaporator. If there truly is no low side pressure, remove the lines from the evaporator and see if you can blow through it.

 

[jakerudy]

After evacuating the system when I go to charge on the high side it won't take more than 1/2can and only gets to about 75-80psi.

Why are you charging the high side?

This.

You can charge on the high side if you shove it in by weight with the a/c off but you have to have the system to do it. Charging from a can you can't overcome the high side pressure. Check a PT chart for R-12 or R-134a to see the temperature you would take the can to in order to charge on the high side. It is much easier to charge the suction side just make sure you charge with vapor. Charge slowly until you get the proper pressure. It can help to put the can in a bucket of warm water as you charge.

Pretty sure the pressure isn't building because there just isn't enough refrigerant in the system. There is no liquid feeding the expansion valve so the compressor is just pushing around a low charge.

 

[88red]

Thanks for the help, it turns out I did have a clog in the expansion valve. The fsm had me dumping liquid in the high side with engine off and I should have seen some pressure migrate to the low side as well. When I loaded vapor into the low side with the engine on it wouldn't take anything more than the initial load. To complicate things my idler pulley seized up in the mix too. I faced the inevitable and pulled the evaporator again and cleared the clog. All is working now. Two cans loaded with high and low side pressures checking out per spec. Temps at the vent in the high 40s.
No 4-40 ac for me this summer!

 

[88red]

This.

You can charge on the high side if you shove it in by weight with the a/c off but you have to have the system to do it. Charging from a can you can't overcome the high side pressure. Check a PT chart for R-12 or R-134a to see the temperature you would take the can to in order to charge on the high side. It is much easier to charge the suction side just make sure you charge with vapor. Charge slowly until you get the proper pressure. It can help to put the can in a bucket of warm water as you charge.

Pretty sure the pressure isn't building because there just isn't enough refrigerant in the system. There is no liquid feeding the expansion valve so the compressor is just pushing around a low charge.

Thanks for the tip. I used your warm water method. Ambient temps today were low and the can just froze up and wouldn't vaporize.

 

[jakerudy]

Thanks for the tip. I used your warm water method. Ambient temps today were low and the can just froze up and wouldn't vaporize.

Glad it helped.