AC High and Low pressure sides reading same PSI. Bad compressor?

[BadgerManBEN]

I have been trouble shooting my AC system and finally got my hands on some gauges. I hooked them up, cranked the AC on and found that both the high and low pressure side were reading about 130 psi. I am trying to figure out why they would both be the same. I am thinking somewhere between the high and low sides inside the compressor is plugged or exploded. I don't know the internals of an air compressor well enough to make a good diagnosis. Anyone have an idea?

 

[Scamper]

Aside from 130psi being low (i.e., system is undercharged), are you sure you had both valves closed when you hooked up the system?

 

[alia176]

This is a good thread as it helps us learn more about our A/C system, at your expense!

If the both valves on the manifolds were closed when the pressure was equal then could it mean that the expansion valve inside the "cooling unit", near the evaporator not functioning properly?

 

[1972FJ55]

Is the compressor engaged, (not just the pulley spinning) when you're checking it? Typically, when the pressures are equal, and the compressor is engaged, then the compressor is bad. That said, those compressors don't usually fail internally without some warning. A more common problem is the engine running hot enough to shut off the compressor.
Rex

 

[CJF]

If the both valves on the manifolds were closed when the pressure was equal then could it mean that the expansion valve inside the "cooling unit", near the evaporator not functioning properly?

No.

That would give too high high side readings and too low low side readings.

 

[CJF]

Is the compressor engaged, (not just the pulley spinning) when you're checking it?

x2.

We need an answer to this to proceed.

 

[alia176]

No.

That would give too high high side readings and too low low side readings.

Ahh copy that. I was thinking if the expansion valve is fully open then the two pressure would equalize.

 

[Tools R Us]

Ahh copy that. I was thinking if the expansion valve is fully open then the two pressure would equalize.

I have never seen one stuck open that allowed the readings to equalize, even wide open there is still a restriction.

Most times if the compressor is blown bad enough to have zero output, it's noisy. It's possible that all of the valves are stuck/broken, but not likely, my guess is it not turning. Is the pressure the same with the motor off?

 

[alia176]

ok, copy that.

 

[BadgerManBEN]

x2.

We need an answer to this to proceed.

The compressor is engaged meaning when I turn on the AC the clutch engages and starts spinning.

 

[BadgerManBEN]

I have never seen one stuck open that allowed the readings to equalize, even wide open there is still a restriction.

Most times if the compressor is blown bad enough to have zero output, it's noisy. It's possible that all of the valves are stuck/broken, but not likely, my guess is it not turning. Is the pressure the same with the motor off?

Pressure is the same when the motor is off.

 

[Tools R Us]

Pressure is the same when the motor is off.

Is the bolt that holds the clutch on tight?

 

[1972FJ55]

The compressor is engaged meaning when I turn on the AC the clutch engages and starts spinning.

Sorry, but if the compressor is engaged and the pressures are equal, then it's time for a new compressor, drier and expansion valve.

 

[murf]

^ X2 compressor bypassing pressures internally.