A/C help

[doucebag]

A guy that I work with is going to check the charge or level of the fluid in my 91 Plus. Where is the valve or hose that you need to check the fluid? Is it the one on the left hand side (looking at the engine from the front)at the back with the pressure valve stcking up? He has never worked on a sho before.

 

[HopefulSHO]

I belive it's the one closest to the firewall.

 

[rangerj]

DB,

The low pressure valve is back by the firewall on the passenger side of the vehicle. It is larger than the high pressure valve and is on the larger "suction" line.

The high pressure line is the smaller line.

The operating pressures should be approximately 50lbs on the low side, and 250 lbs on the high side.

The minimum low pressure needed to activate the low pressure switch is about 20 lbs psi. If the minimum low pressure is not present then the clutch will not be activated. rangerj

 

[doucebag]

Thanks guys, that should help him out alot

 

[sdpatt]

I have found a more consistent charge by checking the pressure of the system with the car cold and the engine not running. That way you can use the temperature/pressure scale on the charging system pressure guage. You can test the static pressure at either the low or high pressure fitting since they will be the same with the engine not running.

For R134a, a system pressure of 100 psig at an ambient temperature of 85F gives my retrofitted system excellent performance. The measured pressure is very dependent upon the temperature of the gas and the system. Too much pressure can impede the A/C system efficiency just as well as too low a pressure. With the high pressure on the low side of the system, the heat absorption capacity of the liquid in the evaporator is reduced and does not allow the gas to expand to its designed pressure. This can severly limit the performance of the system.

Read more here and here.