air system..air compresser

[pete36330]

on my 82 MCI 9,,6v92T..How can you tell how often the air compresser is cycling ...my air pressure seems to stay the same as I'm driving ...but sometimes the pressure  drops to about 90 psi and then climbs back up.. I've tried to listen ,,but I can't tell if its pumping or not ..any suggestions??

[luvrbus]

If it drops to 90 and come back up it is working, depending on the setting 90 to 100 lbs is the cut in pressure .
If you have a dryer you should hear it purge (a blast of air when it reaches the high setting )


good luck

[bevans6]

Exactly.  When the pressure comes down to 90 - 95 and starts back up - that's when it is pumping.  It actually never stops pumping, it's just that when the system is full it diverts the air to atmosphere.  You can't hear any change in noise when it changes, you can normally hear the air dryer purge when it stops pumping at 120 psi or so.  When driving my bus cycles about every 30 - 45 minutes or so if I'm not using any air to speak of for brakes or wipers. 

Brian

[TomC]

Since you hear no sounds, this tells me you do not have an air/water separator.  I would suggest you have one installed, since this removes water from the compressed air and filters it.  Then you'll hear (as previously stated) the woosh of the air being released when the air is up to pressure and the compressor cuts out.  I like this-it tells me without looking I'm ready to go in the morning.  Good luck, TomC