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Old 03-04-2013, 06:25 AM   #5
JohnnieB
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Join Date: Jun 2011
Location: West Virginia
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Default Re: FnR switch high pitch noise

The beeper problem and the voltage problem are separate electrical issues, but may have a common mechanical cause. That being a loose, worn out or maladjusted F/R assembly.

The beeper issue first. The beeper sounds when the roller on the arm of MS-4 (Labeled MS-1 on attached drawing) drops into one of the two indentations on the outer edge (circumference) of the F/R moveable cam.

Unless, in addition to being rotated by the shift lever assembly, the cam is somehow being moved from side to side, I'm not sure why the beeper sounds when the lever is pushed further in the Forward direction. Perhaps the F/R assembly is assembled correctly, or the nut in the red box on second drawing is too loose.
(That nut being too loose might also be causing the voltage and high pitched noise issues)



The voltage problem:
In a Series cart there is a single current path starting at the battery pack's main positive terminal, going though the solenoid to a set of contacts in the F/R switch, then through the stator windings in the motor, then to a different set of contacts in the F/R switch, then through the motor's armature, then to the M- terminal on the controller and through the MOSFETs inside the controller to the B- terminal which is connected to the main negative terminal on the battery pack and then the current flows through the batteries and cables within the battery pack back to the main positive terminal, completing the high current loop.

Any resistance in any cable, connection or set of contacts will develop a voltage drop when current flows through it and reduce the amount of voltage applied to the motor windings.

When the pedal is only pushed until the solenoid first clicks, the MOSFETs in the controller are not conducting (or shouldn't if the ITS is adjusted properly), so the entire battery pack voltage should be dropped between the M- and B- terminals on the controller.

Attached is a schematic of a stock Series cart. The order the high current cables are connected to the A, B, C and D studs on the F/R switch may be different, but the rest of the high current loop is the same.

The first place I would measure is the "A" stud on the F/R switch. That is where B+ attaches to the F/R switch initially.
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