2nd Gen Non-Engine/Transmission Another AC ??

[DieselDoghouse]

Yet another AC question. When is the low pressure reading taken? The engine is warmed up at high idle with hood down and doors open, but has the ac already been running or do you read just as the compressor engages and the gauge settles. I can get a much lower reading by waiting for the system to chill more...

 

[B.G. Smith]

Yet another AC question. When is the low pressure reading taken? The engine is warmed up at high idle with hood down and doors open, but has the ac already been running or do you read just as the compressor engages and the gauge settles. I can get a much lower reading by waiting for the system to chill more...

The reading should be taken with the engine warmed up, the doors and windows closed, the A/C set on max with the temp control set on coldest position, hood mostly closed (just enough gap for the hoses), engine speed set at 1000 RPM, the clutch may cycle depending on the ambient temp. and humidity. If that is a problem the clutch cycling switch can be jumpered. bg

 

[DieselDoghouse]

should it matter then whether the ac is coming on for the first time or HAS been cycling for several minutes? - I get a difference of 8 - 10 psi depending. (The pressure drops as the system chills down).

 

[B.G. Smith]

should it matter then whether the ac is coming on for the first time or HAS been cycling for several minutes? - I get a difference of 8 - 10 psi depending. (The pressure drops as the system chills down).

A note in the performance temperature and pressure section says "if the pressures are lower than shown , but the center panel outlet discharge temperatures are OK, then the A/C system is OK. " And yes, as the temperature in the cab is lowered, the suction pressure will lower. bg