owner of an equipment repair shop, I can divide my customers into two
camps: Those who do trade-ins every year so they only operate new
equipment, and those whose business strategy includes the operation of
older, used equipment. It seems to be an article of faith among the
new equipment devotees that new equipment won't break down. In fact,
though, new equipment does break down, often before you've even put it in
service. Moreover, new equipment has some troubleshooting challenges
of its very own, challenges you never see on old, used equipment.
The most common new-equipment
breakdown I see is sticking spools on the hydraulic valve body of
auto-loading trucks. The spools in such valve bodies, which are
moved in and out by electromagnetic coils, are made with a precisely
machined steel outer diameter to fit in a precisely machined metal bore in
the valve section.
The physical contact between the
spool and the bore is metal on metal -- there is no rubber or plastic
between the two. When the parts are new, the fit between the two is
very close. Sometimes the fit is so close that the spool will get
stuck in one position and the electric coil that moves it isn't strong
enough to dislodge it. Older equipment with many hours of motion and
use in the spools rarely has this problem because repeated use has made
the tight fit a little less tight. When the spool gets stuck, the
wrecker boom will fail to move when you press the button on your remote
Solve this problem by using the
manual override feature which comes on many, but not all, auto-loading
truck valve bodies. The manual override requires you to use two
hands simultaneously. With the engine running, use one hand to move
the spool by pressing in on the round knob on the end of one of the valve
sections (see photo). At the same time, with your other hand,
depress one of the buttons on your remote control.
You have to perform both actions
at the same time in order for the manual override to work. The
wrecker boom will start moving again. If it's moving in the wrong
direction, keep pressing a button on your remote control and with your
other hand simply press the manual override knob on the opposite end of
the same valve section. You have to use the strength of your whole
hand and press hard on manual override knobs to get them to operate --
gentle fingertip pressure will not do the job -- and I usually use my
thumb to maximize the force.
Stay tuned: More
troubleshooting on brand new equipment in my next column.