Cat 257b power at ignition but won't energize start relay

[Andy 9000]

Hello, hoping I can get some advice. I have a Cat 257b tracked skid steer, dash lights come on with ignition in run position but when I turn it to start position it's not energizing the start relay in the engine compartment. I have disassembled the instrument cluster to test the ignition, it is testing good. I've tested the ignition relay and it is also good, just to verify I replaced it with a spare but made no difference. I've tested and verified the seat switch is working, I've verified that the lap bar switch is working (I'm not really sure how to test a 3 wire hall effect sensor, but when it is lifted the dash light for the lap bar illuminates and then goes out when it's lowered so I have to think it's working). I've checked all the fuses, they are good. It's nothing to do with the battery, if I use a jumper wire to energize the output wire of the start relay and have someone in the cab it starts just fine and runs as it should. I tried to trace the wiring but it has been a struggle to follow them through the machine. Would be terrific is anyone has had a similar problem or has a wiring diagram for this machine to share (ser: CAT0257BASLK08627). Thank-you

 

[heymccall]

The 248b schematic in post #2 here is also for your 257b.
https://www.heavyequipmentforums.co...n’-simple-cat-268b-wiring.96888/#post-1075130

 

[Nige]

Close but not quite I'm afraid. That schematic only covers machines up to 8299, the OP has 8627. I'll send you a copy.

 

[bobatack]

Cat skid loaders need a very good battery connection
Would be something simple to check

 

[Andy 9000]

Thank-you for the replies, I've got the schematic from Nige - I'll update when it's solved. Great forum!

 

[Andy 9000]

With the help of the schematic I was able to narrow it down to a section of the harness, where I found a hose had rubbed through the loom and into the wire bundle. Thank-you for your replies, really appreciate the assist with this repair!