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Restoration of Class 119 Driving Motor Brake Composite W51073

A Floating Success

Progress reported on 09/07/12.

This weekend was mainly spent investigating a series of electrical faults starting with a dead short on the stop circuit for the engine that the team had managed to return to running order. As to be expected on a vehicle that has spent so long out of use and has had many different components removed before being saved for preservation, the wiring is in various states. A stroke of luck came in the cab when the wiring was done for the drivers controls but a perplexing problem was found on the engine stop circuit down below. When the stop button was pressed the stop solenoid on the engine didn't operate, instead a fuse blew.

Of course, it wasn't going to be a simple problem to resolve. Not only are electrical problems like this notoriously difficult to find anyway, the vehicle also has several later modifications not on the electrical schematic which have to be fathomed. A good few hours of fault finding ensued. The fault was traced to the niphon plug on the engine itself which had a couple of pins transposed! This had been done at the factory when the engine was built (remembering it is a brand new engine) so putting the pins in the plug back to how they should be got the stop solenoid to operate when the stop button was pressed.

Typically, this created another string of issues that only came to light as a result of fixing the first issue. On attempting to start the engine with a working stop solenoid, the engine would fire and then shut down immediately. This revealed either the oil pressure switch or the coolant float were not doing their job properly. In the engine run circuit are an oil pressure switch which will shut down the engine in the event of low oil and a coolant float switch which floats inside the coolant header tank to stop the engine if the coolant level drops low. Attention turned to the float switch which, just to confuse matters, had stopped working in the couple of intervening years between the team originally wiring that up and this weekend. A refurbished float from stores solved this matter along with some head scratching as some of the wiring for this had the cable labels transposed from yesteryear!

The only other fault to rectify after this was a loose connection inside the fire test box as this is linked to the engine shut down circuit too. If there is a fire then the engine will shut down but similarly there is also a test button for the driver to test that this safety system is working. Whilst the test button was working, there was a fault with the connections on the back of the switch which isolates this system - a new switch was fitted.

It sounds complicated but quick to write about. The team actually spent two days tracing and rectifying these faults. The result, however, is an engine which starts and stops as it should. All three stop buttons (solebar both sides and the one in the cab) work as expected and the fire shut down system is working too! An excellent job! Inside, a start was made on the big window frames with stain and varnish as can be seen in the photograph.


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