Shorts To Frame Test; To Test For Shorts To Frame - Toyota 7BPUE15 Service Manual

Section 5. Troubleshooting

Shorts to Frame Test

Shorts to Frame Test
"Shorts to frame" is a n industry term for
unintentional current leakage paths between
normally isolated electrical circuits and their
metal enclosures.
Shorts to frame may be metallic connections,
such a s a wire conductor contacting metal
through worn insulation. More often, shorts to
frame are resistive "leakage" paths caused by
contamination and/or moisture.
These leakage paths can result in unwanted
electrical noise on the metallic truck structure,
and may result in improper operation.
Shorts to frame can be caused by:
Accumulation of dirt
Battery electrolyte leakage
Motor brush dust
Motor brush leads touching the housing
Breakdown in insulation
Bare wires
Pinched wiring harness
Improper mounting of circuit cards
Shorts to frame can occur a t numerous
locations on a truck, including:
Batteries
Motors
Cables, wiring, and harnesses
Heat sinks
Bus bars
Solenoids
Contactors
Terminal strips
Switches
Power panel insulation
Circuit card mounts
To determine the source(s) of shorts to frame,
begin by testing the battery for shorts to case.
Toyota Orderpicker Model 7BPUE 15 Service Manual
Then test for shorts between electrical
components and the truck frame.

To test for shorts to frame:

1. Turn the key switch OFF and disconnect
the battery connector.
2. To test the battery for shorts to case,
connect a 12-volt test light to the battery
case from battery B+, and then to the
battery case from battery B-. If the light
lights a t all, even momentarily, there is a
serious problem with the battery, either
external contamination or internal
damage. DO N O T continue until this
condition is corrected. Your meter may
be damaged if you proceed before
correcting this condition.
Install another battery in the truck and
repeat this procedure from step 1.
If the test light does not light, continue to
the next step.
With the battery disconnected from the
3.
truck, use a digital ammeter to measure
the leakage current from the battery case
to battery B+ and from the battery case to
battery B-. Begin measuring a t the highest
ampere scale and work toward the lowest.
A reading of more than 0.00 1 A (1 mA)
indicates a serious short. DO N O T
continue until this condition is
corrected. Your meter may be damaged if
you proceed before correcting this
condition.
Install another battery in the truck and
repeat this procedure from step
If the current is less than 0.0002
than 0.0002
0.00 1
A
the truck, then continue with step
Ensure the battery case does not touch
the truck frame during the remaining
tests.
4. With the battery disconnected (or removed
and disconnected) from the truck, use a
digital ohmmeter to measure the
resistance from truck frame to truck B+, to
truck B- (NOT battery B+ and B-), and to
all fuses and motors. A reading of less
than 1000 ohms indicates a serious short.
00700-CL222-05, 1 5 March 2005
1.
A
If the current is greater
4.
(0.2 and less than
A
remove the battery from
(0.2
4.