M927a2 spring brakes.

I got a new too me m927a2 about 2 weeks ago. Working fixing the broke parts and the bugs. 1 of its bugs is the spring brakes have air on the almost continuously. The air valve on the hand brake is the only way to engage them. The dash valve has no affect them. Checked the hand valve and double check valve 3 and 4 there in good condition. The hand valve is not leaking nor does it have back pressure on it. Ideas on where to look next. Yes it has ABS. I'm not find the army manuals air line diagrams helpful.

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jnbru said:

I got a new too me m927a2 about 2 weeks ago. Working fixing the broke parts and the bugs. 1 of its bugs is the spring brakes have air on the almost continuously. The air valve on the hand brake is the only way to engage them. The dash valve has no affect them. Checked the hand valve and double check valve 3 and 4 there in good condition. The hand valve is not leaking nor does it have back pressure on it. Ideas on where to look next. Yes it has ABS. I'm not find the army manuals air line diagrams helpful.

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Dash valve should be pulled out. That is normal operation. Pulling the hand brake up engages the driveline brake and cuts off the air to the spring brakes engaging them via the linear valve. When the parking brake is down then the spring brakes should be released. That is normal operation

These trucks do not have normal parking brake valves like a semi truck. That button on the dash is NOT a parking brake valve. It is simply a bypass in case the valve on the emergency brake handle fails to release to spring brakes it can be depressed in order to charge the spring brakes to get out of harms way.

Thanks for the explanation. I had come to pretty much the same conclusion.