Nilfisk-Advance SR 1900 Service Manual

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Nilfisk-Advance SR 1900 Service Manual Manual pdf 12 page image

10 - FORM NO. 56043123 - SR 1900Symptom: There is no cab heat, or the cab heat cannot be controlled.Note: Before troubleshooting the heating system, make sure the engine is up to normal operating temperature, the engine coolant is at the recommended leveland there are no air locks in the cooling system. (Refer to the To Eliminate Air Locks from the Cooling System subsection.)To Troubleshoot the Valve AssemblyRefer to Figure 4-1.FIGURE 4-1 – Valve Assembly Connector PinsValve Open to Heater Core, HeaterTemperature Control set to Hot (fullclockwise)Ohmmeter Connections Resistance (Approximate)Feedback (+) Pin and Feedback (-) Pin 5.71 kFeedback (+) Pin and Feedback Pot Pin 5.55 kFeedback Pot Pin and Feedback (-) Pin 0.88 kValve Closed to Heater Core, HeaterTemperature Control set to Cold (fullcounterclockwise)Feedback (+) Pin and Feedback (-) Pin 5.71 kFeedback (+) Pin and Feedback Pot Pin 0.48 kFeedback Pot Pin and Feedback (-) Pin 5.63 kValve Halfway Open, Heater TemperatureControl set to approximate midpointFeedback (+) Pin and Feedback (-) Pin 5.71 kFeedback (+) Pin and Feedback Pot Pin 3.14 kFeedback Pot Pin and Feedback (-) Pin 3.25 kIf the6. Feedback Pin resistance values are not close to those shown in the above table, it indicates that the feedback potentiometer in the Valve Assembly isnot working correctly. Replace the Valve Assembly.Valve AssemblyFeedback (+) PinFeedback Pot PinFeedback (-) PinMotor (+) PinMotor (-) PinDisconnect the electrical connector from the1. Valve Assembly.Carefully connect a 12 VDC source to the2. Motor (-) andMotor (+) pins (directly or via the BLK/WHT and ORN wires inthe connector) to run the butterfly valve motor independentlywithout input from the heater temperature control.Check for the heated coolant being switched on and off to3.the heater core. Note that it will take approximately 15-20seconds for the valve motor to run between its full-off andfull-on positions.● If the valve motor isn’t running, replace the4. ValveAssembly.● If the valve motor appears to be running correctly,continue on to step 5 below.Check the resistance through the5. Feedback Pins todetermine if the feedback potentiometer in the ValveAssembly is working correctly. The resistance values shouldbe close to those shown in the table below.