Air brake issue

[remanzi]

Have a 1987 AM General M939A1 5 ton. Air brake pressure should top out at 120 psi. Pressure now runs up to 150psi before the safety valve releases. Thought it was the air governor and replaced it. Did not fix problem. Compressor is working but air is not getting to the governor. Anyone have a similar problem and any suggestions?

 

[simp5782]

Have a 1987 AM General M939A1 5 ton. Air brake pressure should top out at 120 psi. Pressure now runs up to 150psi before the safety valve releases. Thought it was the air governor and replaced it. Did not fix problem. Compressor is working but air is not getting to the governor. Anyone have a similar problem and any suggestions?

Pressure protection valve

Does your horn and wipers work? If no, replace the PPV

If yes, remove the flex line from the governor a d remove the small line at the dryer and blow thru it. Sometimes the cotton jacket line can come apart internally and clog the dryer purge signal line up

 

[remanzi]

Pressure protection valve

Does your horn and wipers work? If no, replace the PPV

If yes, remove the flex line from the governor a d remove the small line at the dryer and blow thru it. Sometimes the cotton jacket line can come apart internally and clog the dryer purge signal line up

Thank you for the quick reply. I will try blowing out the lines and look to replace the PPV if that does not work.