Engine Continues To Run With Key Switch Off Caterpillar

Problem:

Some machines could experience problems with engine shut down when turning the key start switch to the off position. The problem only occurs under two basic conditions.

* When the 3E-5464 A/C thermostat switch circuit opens under normal operation.

* Or when an open circuit occurs on circuit 522. ( A/C Clutch to Thermostat Switch ).

When either of these two conditions occur, current from the A/C clutch group back feeds through pin 2 ( 522 WH ) of the 172-9200 Engine diode block.

This subsequently provides power to pin 4 ( 308 YL ) of the 172-9200 diode block which then energizes the Engine shut off solenoid. The Engine shut off solenoid is powered to run hence the engine may not shut down if one of these two conditions occur.

Solution:

Parts Required.

1. Disconnect and remove the existing 172-9200 4 pin diode block from the Engine harness.

2. Unload the four wires from the 155-2272 4 pin DT plug connection on the harness side.

3. Using two new 155-2270 2 pin DT plug kits reload the four wires removed from the 4 pin DT plug. The 155-2270 Plug kit consists of the 155-2261 Wedge and the 155-2269 Plug Assembly.

4. Install the 155-2261 locking wedge assemblies.

5. Install two new 106-8704 Arc Suppressors onto the harness connections made in step 3

6. Install two new 106-8704 Arc Suppressors onto the harness connections made in step 3.

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