We need to discuss basics of how your system operates.
The compressor is pumping 100% of the time, but when it builds pressure is determined by the D2 governor located on the passenger side firewall under the hood
There’s only a few things that can STOP you from building air,
1) most common is the Pressure Protection Valve located under the truck gets rusty or frozen inside, and will not allow air to pass through to give the “signal” to build air, it’s job in life is to protect your braking ability if you blow an airline on your wipers, horn etc. see picture 1
2) the governor mentioned above, see picture 2, it has a cut in and cut out pressure, generally it cuts in 85-100 psi, closes the compressor valves and the air builds until 120-135 depending on settings and then STOPS building pressure, purges drier, all is good.
3) the compressor unloader valve is an integral part of the head of the air compressor itself. It slides up and down with O rings in the bore, if it gets sticky it can hang up and never build air. This is what you were supposed to spin the line off, on an a2 truck looking at the compressor the line comes off the TOP of the compressor at a 45° angle pointed slightly back towards the cab, it’s like a little 1/4” line or smaller, when you spin that line off, stick your finger on top of the fitting of the compressor, is it “dead” (meaning no air moving) or is it pushing air out then pulling it in?
4) last but not least, the drier commonly sticks open on the purge valve, making people falsely thinking they “aren’t building air” yet the truck is building air, you just have a leak so massive it loses it as fast as it can build it.
There are other things, such as blown unloaded head gaskets and main air compressor head gaskets, faulty discharge lines etc but those are a little more rare.
Since you’ve gotten the truck home, I advise airing the truck up via your deuce or air compressor, and see if your horn and air wipers work. If they don’t and you have 100+ psi of air, there’s your problem. If they do, it’s time to check your governor followed by the air compressor unloader.
Remember, everything on these trucks are stupid simple, accurately go down a diagnostics tree and you’ll find your root cause. Work down that list and let me know
Sent from my iPhone using Tapatalk
The compressor is pumping 100% of the time, but when it builds pressure is determined by the D2 governor located on the passenger side firewall under the hood
There’s only a few things that can STOP you from building air,
1) most common is the Pressure Protection Valve located under the truck gets rusty or frozen inside, and will not allow air to pass through to give the “signal” to build air, it’s job in life is to protect your braking ability if you blow an airline on your wipers, horn etc. see picture 1
2) the governor mentioned above, see picture 2, it has a cut in and cut out pressure, generally it cuts in 85-100 psi, closes the compressor valves and the air builds until 120-135 depending on settings and then STOPS building pressure, purges drier, all is good.
3) the compressor unloader valve is an integral part of the head of the air compressor itself. It slides up and down with O rings in the bore, if it gets sticky it can hang up and never build air. This is what you were supposed to spin the line off, on an a2 truck looking at the compressor the line comes off the TOP of the compressor at a 45° angle pointed slightly back towards the cab, it’s like a little 1/4” line or smaller, when you spin that line off, stick your finger on top of the fitting of the compressor, is it “dead” (meaning no air moving) or is it pushing air out then pulling it in?
4) last but not least, the drier commonly sticks open on the purge valve, making people falsely thinking they “aren’t building air” yet the truck is building air, you just have a leak so massive it loses it as fast as it can build it.
There are other things, such as blown unloaded head gaskets and main air compressor head gaskets, faulty discharge lines etc but those are a little more rare.
Since you’ve gotten the truck home, I advise airing the truck up via your deuce or air compressor, and see if your horn and air wipers work. If they don’t and you have 100+ psi of air, there’s your problem. If they do, it’s time to check your governor followed by the air compressor unloader.
Remember, everything on these trucks are stupid simple, accurately go down a diagnostics tree and you’ll find your root cause. Work down that list and let me know
Sent from my iPhone using Tapatalk
