753 BICS/Traction lock problem

[Litnng]

I can't get the brake solenoid to release. Here is the troubleshooting that I've done. I ohmed out the solenoid and it is as it says it should be on my wiring diagram. Brake relay is also good. I continuitied the white wire from the solenoid plug to the brake relay and also the pink with white wire from the relay to the BICS box. Both are ok. I'm getting about 7.5 volts on the red wire (hold coil) at the solenoid but no voltage on the white wire (pull coil). I can get the solenoid to release the parking brake by putting battery voltage in place of the pink with white wire at the brake relay. Also, I pulled my traction lock override button out and I can't seem to get any continuity across it. Could that be bad and causing this? Also, no light or flashes on the BICS Traction light. Any and all help will be much appreciated, thanks in advance.

 

[mrfixitpaul]

Have you tested the parking brake switch?

 

[Litnng]

Have you tested the parking brake switch?

Yes, the parking brake switch does work, although it doesn't activate my traction lock solenoid. Does anyone know how many volts the pink/white wire from the BICS to the brake relay is supposed to carry? I'm thinking that if the problem is in the BICS itself I may by-pass it and make the traction lock work with the foot parking brake switch only.

 

[mrfixitpaul]

Yes, the parking brake switch does work, although it doesn't activate my traction lock solenoid. Does anyone know how many volts the pink/white wire from the BICS to the brake relay is supposed to carry? I'm thinking that if the problem is in the BICS itself I may by-pass it and make the traction lock work with the foot parking brake switch only.

Not sure on the voltage of the white wire, I'd guess 12 volts just to activate the relay but it will only be momentary as that is for the pull circuit. I'm sure yuo have already checked the brake fuse as well but sometimes they corrode and look ok but won't allow voltage to pass under load. If you want to simply have a switch you'll still need to install a timer for the pull circuit, as this coil will burn out very fast if you give it power for too long(probably a couple of seconds would kill it). You could install a timer that bobcat uses on the fuel solenoid on the kubota engines, or to be really frugal wire up the hold coil to the park brake switch and then use a momentary switch for the pull coil. Then to release the brake first engage the hold coil and leave on, then the pull coil for just a split second. Very confusing to put in writing but not too bad if you understand how the system works.

 

[Litnng]

Not sure on the voltage of the white wire, I'd guess 12 volts just to activate the relay but it will only be momentary as that is for the pull circuit. I'm sure yuo have already checked the brake fuse as well but sometimes they corrode and look ok but won't allow voltage to pass under load. If you want to simply have a switch you'll still need to install a timer for the pull circuit, as this coil will burn out very fast if you give it power for too long(probably a couple of seconds would kill it). You could install a timer that bobcat uses on the fuel solenoid on the kubota engines, or to be really frugal wire up the hold coil to the park brake switch and then use a momentary switch for the pull coil. Then to release the brake first engage the hold coil and leave on, then the pull coil for just a split second. Very confusing to put in writing but not too bad if you understand how the system works.

PROBLEM SOLVED! Paul, your question about the park brake switch got me thinking. I had checked the continuity of the switch but I had not checked the plug in the main harness. Sure enough, one of the pins in the main harness to the park brake was not locked into the plastic plug as it should have been. Once I snapped it in, everything works fine. I love the simple fixes. Thanks for the help!

 

[Daveb68]

Have you tested the parking brake switch?

You should see the red light up inside the switch light up when brake is engaged.