I can talk from experience that I had a few service calls that involved the vandalock system. When engaged the bus will not start which is the main reason they were installed. They interrupt the starting circuit until they are unlatched at either the side door or rear emergency window.
This pertains to the pusher school bus only. The latest conventional buses have these systems at the entrance door and the rear exit door. If you try to start a pusher bus with the vandalock engaged the warning buzzer will remain on and the starter will not engage until the latch is opened.
There is a switch that the bolt style latch contacts to either create a closed or open circuit in the starter operation system. The C2 conventional buses have a sliding arm that does the same thing at the rear exit door. Many times this arm has accidentally engaged the vandalock circuit while the driver is checking the rear door operation during the pre-trip and post-trip routine.
The latch assembly is lubricated with a light grease so the door latch and the vandalock latch slides independently from each other. On a cold morning however they may slide together because of the thicker consistency of the lubricating grease and the bus does not start.
I’ve seen this occur so many times that I can confidently talk the driver out of trouble over the 2 way radio. You hear the problem their having and right away the light bulb comes on and trouble is soon diverted. International and Thomas buses will both sound the buzzers or alarms along with a no start condition. That is the first sign…. then look at the entrance door and rear door vandalock on a conventional school bus or the rear emergency / side door vandalock assembly on a pusher school bus.
Thank you for reading and I hope this will help you get out of trouble some day if this scenario happens to you. Ask your questions below or just post a comment. Join the mechanicshub.com site and I’ll see on the inside.