Case SR220, SR250, SV250, SV300 SkidSteer Repair Manual (Tier 4A)

Model:
SR220 (PIN: NDM457559 and above) (Tier 4A)
SR250 (PIN: NCM442784 and above) (Tier 4A)
SV250 (PIN: NDM460776 and above) (Tier 4A)
SV300 (PIN: NCM445399 and above) (Tier 4A)
Manuals: Service Manual
Contents
Introduction
Engine
Front Axle System
Rear Axle System
Hydrostatic Drive
Brakes and Controls
Hydraulic Systems
Frames and Ballasting
Wheels
Cab Climate Control
Electrical System
Front Loader and Bucket
Platform, Cab, Bodywork and Decals
Specials Tool Index
Manual Extract: Brake control solenoids – Overview

Solenoids work in much the same way as relays, except that the iron core is not fixed in place. As a result, the windings in the control circuit cause the iron core to move. In the starting system, for example, the movement of this core is used to send large amounts of current to the starter motor.

A solenoid is basically a winding around an iron core. In the Centre of the core there is a plunger which is free to move through the core. When an electrical current passes through the winding an electro-magnetic force is produced which causes the plunger to move through the core. If the current is switched off, the magnetic force is stopped and the plunger is returned by a spring.

The solenoid plunger may have different uses: the most common are moving a hydraulic spool or a mechanical lever.
The MOST COMMON FAULTS that can occur are:

Short circuit winding: if a section of the winding allows the current to pass directly from positive (+) to negative (-) terminals without passing through the winding, this will cause the relevant circuit fuse to blow.

Broken winding: causing an open circuit, it will not allow the current to pass through the winding, so the solenoid will not operate.
Seized plunger (and/or connected components): the solenoid will only move the plunger if all components are free to move.