Re: On board air

[tsm1@domain.elided (Tom Mandera)]

Thinking about this 200psi stuff and pressure switches...

Howard mentioned the compressor running 50 to 250psi in the Air Conditioning
system.

I brought up a 200psi switch.. (I'll probably back off and run the 150psi
like everyone else.. ) but..

If I run a 175/200psi switch and a tank attached, then start using.. some
air.  Say I use enough to drop the tank pressure to.. 150psi, which is below
the switch kick-on.

This is all very simple and we understand this.

BUT.. my 196 is *idling*, and now the compressor has the clutch engaged
(need to up that PSI), but the compressor is NOT putting out 150psi.. it's
pushing 50psi... or trying to.

What happens?

I now have 150psi pushing against the compressor, tyring to push out 50psi..
this doesn't sound very pretty.

If I let the truck idle for a long time (maybe I'm warming it up on a cold
morning after using the air tools last night), the compressor will never get
above 50psi.. it'll just sit there and FIGHT with the tank until I jump in,
punch the throttle and tear out of the driveway to work. :-)

Or, maybe I'm sitting on a trail, idling up, or just waiting in "traffic" at
the foot of an obstacle, and this situation occurs.

This looks like bad news for the compressor, possible premature clutch
failure, maybe some seals.. what do you think?

This might be another good argument for moderation.. and a 90/125psi switch. :-)

-Tom Mandera, Helena MT