Higher Air Pressure For A2 Than A3 At Emergency Port

[glcaines]

While replacing a rear wheel on my M35A3 with one I picked up from Big Camo Truck, I needed to use my 3/4' impact wrench to loosen the lug nuts. I hooked up to the emergency port on my A3 and was only able to remove one lug nut. Raising the RPM to 1500 allowed me to get another one loose. I was very surprised as I routinely use the same impact wrench using the air from my A2 and I have never had difficulty removing lug nuts from deuces. I then backed my A2 up to the A3 and again went after the remaining lug nuts using the same impact wrench hooked up to my A2's air. With the A2 air supply, the remaining lug nuts came loose immediately. My impact wrench definitely developed more torque.

As far as I know, the air supply on the A3 is working correctly and I was reading 120 PSI on the gauge. Has anyone else seen this issue with the A3 air versus A2 air pressure? As a side note, I have now discovered that one of my wheel valves on the A3 is bad. At least it's relatively easy to replace.

 

[glcaines]

No ideas why A2 air is stronger than A3 air?

 

[gimpyrobb]

Too many variables. Air gov. could be set different, air comps. could be(are) different, crust in the lines, and on and on. Not everything is/will be the same. You even have that with (human)twins.

 

[DieselBob]

Sounds like a SCFM problem and not a PSI problem. Are the air tanks the same size or bigger on a A3. Size of the air lines and shutoff valve ports could be an issue.

 

[tm america]

Might have something to do with the fact the a3 has air running to two airpacks and the power steering.. There might be some kind of by pass to keep from loosing the power brakes ?Just my guess..

 

[gimpyrobb]

Might have something to do with the fact the a3 has air running to two airpacks and the power steering.. There might be some kind of by pass to keep from loosing the power brakes ?Just my guess..

and ctis too!

 

[tm america]

and ctis too!

ya forgot about that one.....

 

[G-Force]

Also, don't forget the air dryer and if I'm not mistaken one of your tanks is partitioned in the middle. This basically makes it a 3 tank system.

 

[AceHigh]

My A3 shows zero air until it suddenly jumps to 120. I was just guessing it is a very different system. Guess I better read up on it.

 

[renovate7]

Just wanted to add a comment that my A3 air gauge also stays at zero and then jumps to 120. This truck is new to me and finding out what is "normal" is an on going process.

 

[Heavysteven]

I say the A2 has less restriction from the air compress to the glad hand.

Or is this thread a reason to make us all drool over your trucks? I want an A3 some day.

 

[glcaines]

Just wanted to add a comment that my A3 air gauge also stays at zero and then jumps to 120. This truck is new to me and finding out what is "normal" is an on going process.

Mine stays at zero psi and then jumps to 120 as well and every A3 I've seen does the same thing. I've been told that this is normal, but I don't know why. I'm going to study the A3 compressed air system in detail and find out what is going on. I really don't think anything is wrong with the A3 compressed air system, it is just different than the A2 and more complex. I checked the pressure at the emergency port for both the A2 and A3 and the pressure is similar. The volume of delivered air is definitely not similar. It may be that my impact wrench uses such a high volume of air that the system thinks there is a leak and restricts air flow to reserve sufficient air for the brakes. When my impact wrench winds down and comes to an almost complete stop, my low pressure buzzer is not sounding and the pressure gauge still reads 120 psi. Unfortunately, it is not convenient to have enough air to run my impact wrench. It also takes longer to inflate a tire with the A3 air. I've been spoiled by the A2 compressed air system. However, I do like the dry air from the A3.

 

[mktopside]

My A3 shows zero air until it suddenly jumps to 120. I was just guessing it is a very different system. Guess I better read up on it.

Same here. The rear emergency glad hand I believe shuts off if the truck pressure get's below a certain point. I was filling up my tires the other day and when I was done I disconnected the glad hand then opened the valve just to see how much air flowed out. It was a quick puff, then it abruptly stopped. I crawled under the truck and opened the tank drains, and the tanks still had air in them. All I can assume is that the Air governor cuts off everything except for the brakes at 60psi.

Not directly related, but close. You can back feed the glad hand with a compressor, leave the engine off, master power on, and the CTIS will do it's thing and fill the tires. Not that this is fantastic new info...... but in case you wanted to know, it works.

 

[AceHigh]

That is great info! I will use it soon. Tnx

 

[Pooch1128]

Same here, we have two A3's and both start at 0 with low air buzzer sounding and then boom reads 120 and no buzzer....

 

[m-35tom]

you are comparing apples to oranges.

tom

 

[glcaines]

you are comparing apples to oranges.

tom

I agree. There are more differences between the A2 and A3 than a lot of people realize. That being said, I do like both trucks.

 

[mktopside]

If Humvee's and CUCV's have separate forums........

Just sayin...