The Rusty Bolt Syndrome


I have for some time been having trouble with my Cat track loader refusing to register the safety arm bar status. Basically if the safety bar light stays on you go nowhere and cannot proceed with the start up sequence. I found a high resistance connection on the bonding strap between the tilt cab and the main frame of the machine. The clamping bolt was very rusty. The current path is via the underside of the bolt head and through the bolt threads to the internal threads of the weld on boss on the machine main frame. All the threads were cleaned and loaded with anti seize, all assembled and worked correctly first time. I think that galvanic corrosion had caused the high resistance joint. We all know about this type of problem but sometimes we forget. BEWARE THE RUSTY BOLT !!!!


Staff member
Good find. I remember my Dad getting some very odd lighting effects with his caravan hire fleet when the chassis connection was crook. Some early vans relied on the chassis to tow ball for the return path. A good solid wire connection from each light to the car via the plug and socket fixed it.


Staff member
Had a guy ring me last weekend when his scissor lift wouldn't start, the relay that pulled in power to the starter solenoid just buzzed, He checked the battery and starter switch, the voltage was dropping below the minimum to pull the relay in when the starter solenoid energized. Tracked it back to a rusted out ground connection. Angle grinder to clean up a spot of bare metal for the earth connection, problem fixed.