Section 5. Troubleshooting
Toyota Orderpicker Model 7BPUE 15 Service Manual
Shorts to Frame Test
Shorts to Frame Test
Then test for shorts between electrical components and the truck frame.
"Shorts to frame" is a n industry term for unintentional current leakage paths between normally isolated electrical circuits and their metal enclosures.
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 NOT 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. 3. With the battery disconnected from the 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 NOT 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 current is less than 0.0002 A (0.2 mA), go to step 4. If the current is greater than 0.0002 A (0.2 rnA) and less than 0.001 A (1 rnA), remove the battery from the truck, then continue with step 4. 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.
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.
00700-CL222-05, 1 5 March 2005
