Air volume question

[dslucas]

So...I am out yesterday starting and warming up the deuce. Temps were going to drop low last night and we got a small amount of snow. I fired it up, warmed it up and the air pressure low alarm buzzer went off like normal. Since it was sleeting/snowing at the time, I turned on the pneumatic windshield wipers, then left the truck idling and went inside to grab my coffee cup. When I got back outside, coffee in hand, the low air alert was going off again. Pressure was slightly below 60. I turned off the wipers and the compressor pumped it up again a minute or so later and the alarm went back off. Question being- is this normal? Do the wipers actually use that much air or do I have a weak compressor?

 

[zout]

A dumb question on my part so excuse me - every time you fire up and run the engine have you maintained the air tanks by manually draining them ? Of all moisture.

 

[dslucas]

Yes. I drain the tanks EVERY time I shut the engine off...no exceptions.

 

[ATPTac]

Do you have any air leaks? Best way to tell is to let the tanks fill up all the way, shut the truck off and listen for any hissing. Another thing to check would be your air governor... how much air pressure does the truck build up when the tanks are full?

 

[dslucas]

I shut the truck off and listened for leaks...could not find any. Air system will stay pressurized for hours as long as I don't bleed it off. Never tried leaving it overnight to see if it holds pressure because I am in the habit of draining the tanks every time I shut it off. Seems to build air pressure up to 80psi or so if left alone. Maybe I need to check the governor. I drove it for about 2 hrs Saturday and it never lost pressure just using the brakes.

 

[ATPTac]

80psi is a little low. I'm pretty sure (somebody correct me if I'm wrong) that the range is supposed to be 90-120psi. That could be part of your problem.

 

[SCSG-G4]

Could be as simple as the truck was only running at idle, and the wipers were using more than the air pump at idle could supply?

 

[dslucas]

Very possible. Next time I start up the truck and let it sit I'll double check what pressure the compressor maintains.

 

[DieselBob]

TM 9-2320-361-20

8-29. AIR COMPRESSOR GOVERNOR MAINTENANCE (Contd)​

c. Check and Adjustment​

1. Start engine and buildup air pressure (TM 9-2320-361-10) until gage (4) reading is steady.​

2. Check air pressure. Gage (4) should read 85-120 psi.​

 

[dslucas]

Easy enough....pull off the cap, loosen the jam nut and turn screw. I'll check tomorrow what pressure it builds while running and adjust if needed.
Thanks DieselBob. It appears that I didn't download that manual. I have it now though.

 

[ivbeenrokd]

I know mine will turn the buzzer on if I've been driving and pull into a parking lot while working the steering and brakes a lot to get parked. (I've got the air assist on it)

 

[doghead]

Don't trust the dash gauge, confirm the air pressure with a known good gauge.

 

[18operator]

Mine is right close to 120 psi...

 

[mjtracy]

I have mine set to 120. Also I have noticed at idle, compressor will not keep up with much air usage. I usually use the throttle hold to keep RPMs at 1000 - 1200 if I'm doing anything using air.

 

[dslucas]

I am starting to think it was becuase I had the wipers turned up high and the engine running at idle (about 800rpm). Compressor builds a little less than 120 psi. Checked it with a brand new guage as Doghead suggested. I guess the compressor doens't put out near the volume of air that I am used to.

 

[ATPTac]

I am starting to think it was becuase I had the wipers turned up high and the engine running at idle (about 800rpm). Compressor builds a little less than 120 psi. Checked it with a brand new guage as Doghead suggested. I guess the compressor doens't put out near the volume of air that I am used to.

These compressors are most definitely low volume. Think about it, the two air tanks on the truck are relatively small and it takes about 5+/- minutes for them to fill. There are some threads about adding in additional air tanks for more capacity, granted it will take longer to fill them.