I have a Freightliner that the air dump on the bottom of the air dryer does not close properly after it vents air. If I push and hold the valve in it catches and holds the air but it is a problem if it occurs when driving as my air pressure drops. Does anyone know where the electrical signal comes from that is supposed to activate the dump valve and hold it.
Air brake problem
- Thread starter madimoo
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ModMech
Platinum Member
There is no electrical signal, the airing is for the heater to keep all that water from freezing in COLD weather.
I'm going to guess you have a Bendix "AD-9" air drier, at least I hope so.
There should be a LARGE brass looking nut on the BOTTOM of the drier with a fitting comming out of it (discharge hose). After you drain the air tanks completely, carefully remove the hose and fitting from the brass nut looking thing. Then remove the nut, there is no air pressure now so nothing to worry about. Clean the whole assembly (nut and contents) with ether or brak-cleen and re-install everything. The air system should now work normally again.
I'm going to guess you have a Bendix "AD-9" air drier, at least I hope so.
There should be a LARGE brass looking nut on the BOTTOM of the drier with a fitting comming out of it (discharge hose). After you drain the air tanks completely, carefully remove the hose and fitting from the brass nut looking thing. Then remove the nut, there is no air pressure now so nothing to worry about. Clean the whole assembly (nut and contents) with ether or brak-cleen and re-install everything. The air system should now work normally again.
Wis Bang
Gold Member
If cleaning doesn't work, you may need to replace those parts...usually it is dirt but they can wear out too!