JLG 800A_AJ Service Manual - Manual (Page 168)

SECTION 3 - CHASSIS & TURNTABLE
3-112 – JLG Lift – 3120858
4. No speed signal to Governor.
5. Damaged Controller or Actuator.
(1.) No power - Use a multimeter to check for 12-15 VDC
between terminals A & B on the controller. Check during
engine off and engine running conditions. If voltage is
absent or low, check for:
a. Wiring error.
b. Hook-up on wrong side of ballast resistor.
c. Low battery.
d. Bad voltage regulator.
e. Bad ground connection.
f. corroded terminals.
g. Undersized wiring.
(2.) Incorrect Linkage - Re-check linkage. The freedom of
movement and lack of play are important.
(3.) Incorrect Electrical Hook-up - Re-check all wiring and
connections to the Actuator and Controller against the
supplied schematic.
(4.) No speed signal to Controller.
a. Check the voltage between terminals C and
ground and D and ground of the 8 pin connector
with the engine running. You should see 5 - 30
VDC.
b. The above checks do not guarantee a good
speed signal, but their absence proves that
there is a problem.
(5.) Incorrect Electrical Hook-up - If steps 1 - 4 above have
not revealed the problem, the governor may have been
damaged, either in shipping or during hook-up and test.
• Governor reacts, but can’t be set up to give proper
performance.
This kind of trouble usually falls into three main catego-
ries:
1. Actual Governor malfunction.
2. Governor installation problems and improper adjust-
ment.
3. Governor not tuned or adjusted for engine/applica-
tion.
NOTE: Assure the engine is operating properly by running
engine manually. The Governor will not control any
poor running engine.
(1.) Actual Governor Malfunction - The Governor was
engine-tested for proper operation just prior to being
shipped. Unless damaged in shipment or by improper
handing, it should be serviceable. To check for proper
operation proceed as follows:
a. Once again, disconnect fuel system linkage
from Governor output arm and control engine
manually.
b. Start engine, hold at a low speed, Governor arm
should move to full-fuel position.
c. Increase engine speed carefully. At some engine
speed, Governor arm should move to low-fuel
position.
d. By carefully varying engine speed, you should
be able to cause the Governor arm to pause
momentarily near the middle of its travel. This
engine speed is the speed for which the Gover-
nor is adjusted. If grossly incorrect, reset High
Engine Pot.
e. With the engine running at low speed, move the
Governor arm throughout its stroke by hand.
You should feel a constant smooth force in the
on direction. No binding or rubbing should be
felt within the Governor.
If steps 1a. thru 1e. can be accomplished as described,
the Governor is probably OK. It recognizes underspeed,
overspeed, onspeed and is not binding internally.
If the above steps cannot be accomplished satisfactorily,
there is probably an actual Governor malfunction.
a. Governor is unable to move fuel system freely
(not enough Actuator force available). If Gover-
nor doesn’t move fuel system to on far enough
to provide sufficient fuel but Governor arm
moves far enough when disconnected look for:
1. Linkage binding or misadjusted.
2. Low voltage at Governor during operation.
NOTE: *Measure the voltage as discussed previously and
observe voltage during operation. If Governor fails to
move full on and voltage dips over 1 volt, check for
undersize wire (should be #16 minimum).
3. Excessive force at Governor during engine running,
particularly on carburetor engines.
NOTE: *Carburetor butterfly valves are loaded by engine
vacuum during running, which can add considerable
force not present when engine isn’t running.
NOTE: *Springs in the system; carburetor return springs,
acceleration pump springs, etc., are not usually
needed and can cause governing problems.
b. Governor is unstable at light-load or no-load.
See “Linkage” for carbureted engines.
c. Governor experiences sudden, momentary
spikes toward max. at random intervals, then
recovers.
1. Look for loose wiring or momentary shorts in wiring.
Noise or occasionally missing speed signal.