If you do not get some kind of command of the TM's (Technical manuals) you will
be seriously handi capped for life working on your truck. Sure guys will help
but the TM teaches you so much more. I have an IPAD w/ all the TM's loaded
on it and it is in the truck anytime I drive it in case I break. They CAN get
you up and running instead of calling a tow=EXPENSIVE!
I have been thru the exercise you are doing and I could write 3 pages of
how to's but you will be much better served to read the TM's.
They are free and available in the TM section here.
There are 2 low air "switches" one on the primary and one on the secondary
air tanks, they have a ground (55 wire?) , then a wire up to
the FWCM. I pulled my ground and cleaned it and replaced both air switches and
tested the wires just like the TM says to do and then I replaced
the FWCM and now mine works but if you do not know how it
does what it does, again your handicapped. That is a full blown air brake
truck. A Commercial Class B license is required most everywhere
you drive it. If you are worth a few dollars you should RUN and get
a CLASS B so incase you wreck you do not get sued and loose over that
little technicality. Getting a Class B will teach you a LOT about your
air brake system as well. You will thank me if you go to a professional
truck driving school and learn what is required knowledge to legally
drive these things on most roads per Federal Law ....
The TM's take you on a step by step how to for repairs.
There is an OPERATORS MANUAL TM xxxxx-10 I think, it tells you a lot
but no big time how to repairs.
There are 3 volumns of PARTS
There are 4 volumns of Maintenance
There are 5 Volumns of Field maintenance.
and more, the above is about 10,000 pages. Yep!
It is a daunting task, just start and try to remember what is where
for future use.
Here is a gentle nudge
CLICK HERE
The M939 is a Series of trucks
Look at the passenger side dashboard and tell us what model you have!
M923?
M923A1?
M923A2?
M925?
M925A1?
M925A2?
M936?
M936A1?
etc te al