parking brake won't release on Bobcat 553

[rimrock]

I have a 1998 553 (F series) with BICS controller and the push to start button, no seat sensor. The 553 has been working fine, this problem just started after it was parked outside for a few months. Now the parking brake (traction lock) won't release when I press the push to start button. The battery was bad, so I replaced the battery and cleaned the terminals, and installed a new parking brake solenoid. All the lights come on on the BIC controller, but the parking brake won't release. I have tested the foot switch for the parking brake, and it is working correctly. I don't hear any sounds when the push to start button is pressed. I would check the parking brake relay, except I am not sure which one it is, there are no labels. I checked all the fuses, they appear to be fine.

 

[rimrock]

I forgot to mention, the bucket raises, tilts and lowers just fine, it is only the traction lock that is acting up. The 553 will only move forward and back maybe 3 inches.

 

[rimrock]

I forgot to mention, the bucket raises, tilts and lowers just fine, it is only the traction lock that is acting up. The 553 will only move forward and back maybe 3 inches.

I figured out that the brake relay was the one furthest to the front and the glow plug relay was next to it, by checking wire colors from the schematic. But swapping relays did not help, the problem still exists. Did Bobcat ever publish revised wiring diagrams and BIC maintenance pages for the repair manual after they introduced the push to start button? I have an extra relay in the engine compartment not shown on the wiring diagrams, and I am surmising that it was part of the upgrade that eliminated the seat sensor. Its hard to troubleshoot when you don't have a wiring diagram that is correct.

 

[Tazza]

I figured out that the brake relay was the one furthest to the front and the glow plug relay was next to it, by checking wire colors from the schematic. But swapping relays did not help, the problem still exists. Did Bobcat ever publish revised wiring diagrams and BIC maintenance pages for the repair manual after they introduced the push to start button? I have an extra relay in the engine compartment not shown on the wiring diagrams, and I am surmising that it was part of the upgrade that eliminated the seat sensor. Its hard to troubleshoot when you don't have a wiring diagram that is correct.

You have done everything i'd do.
The next step may be to use a meter to check if you are getting power to the park brake solenoid. You can jump it to make sure the solenoid is working. Run a jumper to the black wire -ve then the white and black are pull and hold, i don't know what is what. Touch the +ve wire to one wire and see if the solenoid snaps back, if not, try the other. The one that makes a loud clunk is the pull, the other is hold. If you put a wire on the hold and brush another on the pull, it should stay held in place. Let the power go and it will put the brake back on.
You checked/swapped the relay, is there a fuse too?
I can't tell you what the extra relay is for, it could be an addition the previous owner installed?

 

[rimrock]

You have done everything i'd do.
The next step may be to use a meter to check if you are getting power to the park brake solenoid. You can jump it to make sure the solenoid is working. Run a jumper to the black wire -ve then the white and black are pull and hold, i don't know what is what. Touch the +ve wire to one wire and see if the solenoid snaps back, if not, try the other. The one that makes a loud clunk is the pull, the other is hold. If you put a wire on the hold and brush another on the pull, it should stay held in place. Let the power go and it will put the brake back on.
You checked/swapped the relay, is there a fuse too?
I can't tell you what the extra relay is for, it could be an addition the previous owner installed?

OK, problem solved. Keep digging and you will eventually find the cause. There was voltage to the brake relay, but none to the solenoid. So I pulled the control console on the upper left side of the cab, and a rodent had obviously been making it a home. Several wires had bites, and the two wires to the push to start button were severed. Reconnecting them solved the problem. However, it was good I took a look, the glow plug switch had corrosion on the back side and one of the spade connectors broke off just from moving the wires. I soldered another spade connector to it, we'll see how long it works.

 

[rimrock]

OK, problem solved. Keep digging and you will eventually find the cause. There was voltage to the brake relay, but none to the solenoid. So I pulled the control console on the upper left side of the cab, and a rodent had obviously been making it a home. Several wires had bites, and the two wires to the push to start button were severed. Reconnecting them solved the problem. However, it was good I took a look, the glow plug switch had corrosion on the back side and one of the spade connectors broke off just from moving the wires. I soldered another spade connector to it, we'll see how long it works.

Well, I spoke too soon. I tested the new solenoid by connecting it to the wiring harness and pressing the push to start button, and it engaged when the piston had about 1" of travel. However, after installing it it is not engaging, so I suspect the problem is insufficient voltage. The hold voltage is fine, the problem is the high voltage side. When I installed the new battery I cleaned the battery terminals and the alternator terminals, and when I inspected the brake relay I checked all the terminals, no corrosion. I noticed that one of the wires going to the brake solenoid is part of the BCIS circuit, but I don't understand that part of the circuit since it is not shown in the wiring diagram. It is the pink/white wire. Is that the wire that carries the high voltage to engage the solenoid? Where should I look for voltage drop in that line?

 

[Tazza]

Well, I spoke too soon. I tested the new solenoid by connecting it to the wiring harness and pressing the push to start button, and it engaged when the piston had about 1" of travel. However, after installing it it is not engaging, so I suspect the problem is insufficient voltage. The hold voltage is fine, the problem is the high voltage side. When I installed the new battery I cleaned the battery terminals and the alternator terminals, and when I inspected the brake relay I checked all the terminals, no corrosion. I noticed that one of the wires going to the brake solenoid is part of the BCIS circuit, but I don't understand that part of the circuit since it is not shown in the wiring diagram. It is the pink/white wire. Is that the wire that carries the high voltage to engage the solenoid? Where should I look for voltage drop in that line?

I'd trace the momentary wire back to the relay. If you have hold but not pull, it has to be there somewhere.
Sadly, i don't remember the colour codes for the wires. Pink white does ring a bell, i'd look for thicker wires that feed the brake. As this is the pull wire that you need, it has to handle higher current. It may help locate it.

 

[ijacobi156]

Thank you for this thread, this is my exact problem , including BCIS all showing green lights, in Sept/2023. I will check all these things. I put a new battery in, but we got this machine when we bought the property. Used it all last winter.