1978 wiring diagrams

[wackercattle]

Hello!
I'm new to the bus world. I have a 1978 bird and it sat 17 years. I have been chasing electrical gremlins. I drove it home all the gauges worked. I had to clean the big grounds in the back to get it to start. I repaired some taillight wiring thats broke. I did not have brake lights so this is my rabbit hole!
I have been tracing and testing wires and breakers, I have taillights, but something is wrong and shorting out my three wires on the bottom of the 81 bus bar. When I unhook those 3 I have no gauges. I'm thinking it's in the air switches but without diagrams I'm lost.
Anyone know where I can buy a diagram? I have the manual and it explains each circuit, but I can't seem to find my short.
Anything helps!
Thanks

[beltguy]

Welcome to our forum.

To my knowledge the only wiring diagrams are in the maintenance manual and it sounds like you have that.

One issue we all deal with is how much of the original wiring is left after the conversion and how many "wiring workarounds" have been made.

Re the brake light switch:  if they left it in stock location is will be in the lower outside compartment under the driver area.

One of my most used wiring testers is an air brake buzzer:  (Amazon Link)  It can be a great tool to test circuits which have termination in the back of the bus and you are working in the front.  You can insert a small 12V battery in the tester wiring to test continuity or leave the battery out to test voltage at the far end.  It is fairly loud and in a frequency range that most "older" folks can hear {grin}

Jim