Bobcat A8105 (81-05) Fault Code: ACD/RACD Output “B” Short to Battery
Also shown on the panel as 81-05 · Also called ACD Output ‘B’ Short to Battery, ACD/RACD Output “B” Short to Battery
ACD/RACD Output “B” Short to Battery · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
Bobcat code A8105 (panel display 81-05) means the ACD/RACD controller detected voltage on Output "B", controller pin J1 B-7, when that output was not commanded on. The controller disables Output "B" when this happens. This affects skid steers, compact track loaders, and excavators equipped with Attachment Control Devices.
Medium severity. Output "B" is disabled once the code sets, which means the attachment function tied to that output will not work until the fault is fixed. It is not an engine-damage or safety-shutdown event by itself, but a disabled attachment output can stop work and may affect attachments that rely on electrical control for safe operation.
What does Bobcat error code A8105 mean?
A8105 is set by the ACD (Attachment Control Device) or RACD (Remote Attachment Control Device) controller when it sees voltage present on Output "B" (controller pin J1 B-7) at a time when the controller itself did not command that output to be active. In plain terms, the controller expects that circuit to be dead unless it turns it on, and it is finding voltage there anyway, usually because something is feeding battery voltage into that circuit from outside the controller's control.
When this condition is detected, the controller responds by disabling Output "B" entirely. That means whatever solenoid or function is wired to Output "B" will stop functioning until the fault clears and the code is reset.
This code applies to Bobcat E35, E42, E45, E55 excavators and S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870 skid steer and track loaders equipped with ACD/RACD attachment control systems.
What triggers a Bobcat A8105 code?
The condition for the code to set is simply key switch or run/enter switch on, at which point the controller monitors Output "B" and flags the fault if voltage appears there without being commanded.
Common causes of A8105
- Output "B", controller pin J1 B-7, shorted to battery voltage.
- Return wire, controller pin J1 A-10, shorted to battery voltage.
- A failed Output "B" solenoid.
- A fault in the ACD/RACD controller itself.
- Moisture, corrosion, or pushed-back pins in the ACD/RACD controller connectors, mainframe harness, attachment control harness, or the Output "B" solenoid connector.
- Intermittent causes that may not be found if the fault is not active during testing, including loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these problems.
How to troubleshoot Bobcat A8105: first checks
- With key switch on, check for voltage on Output "B" (controller pin J1 B-7) when the function is not commanded, to confirm the short-to-battery condition is present.
- Inspect the ACD/RACD controller connectors, mainframe harness connectors, and attachment control harness connectors for moisture, corrosion, or pushed-back pins.
- Check the return wire at controller pin J1 A-10 for a short to battery voltage.
- Inspect the Output "B" solenoid and its wiring for signs of internal shorting or chafed insulation that could be feeding battery voltage into the circuit.
- If the code is not currently active, wiggle-test connectors and harness routing near the ACD/RACD controller and attachment harness to try to reproduce an intermittent short.
- If wiring and solenoid check out, suspect the ACD/RACD controller itself as the source of the fault.
How the code clears
Cycle power (turn the key switch off and back on) once the repair is complete. No separate clearing step beyond a power cycle is listed for this code.
Affected models and serial ranges
A8105 appears in our records across 20 Bobcat models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| E35 | SN A93K110001-99999, SN AC2P11001-99999 |
| E42 | SN AG3411001-99999 |
| E45 | SN AG3G11001-99999, SN AHHC11001-99999 |
| E55 | SN ARWM11001-99999, SN ASW311001-99999 |
| S510 | SN A3NJ11001-99999, SN A3NK11001-99999, SN ATZC11001-99999 |
| S530 | SN A7TV11001-99999, SN ATZD11001-99999 |
| S550 | SN A3NK11001-A3NL99999, SN A3NM11001-99999 |
| S570 | SN A7U711001-799999, SN A7U811001-899999 |
| S590 | SN ANMN11001-99999, SN ANMP11001-99999 |
| S630 | SN A3NT10001-12369, SN A3NT12370-99999, SN A3NU11001-11111, SN A3NU11112-99999 |
| S650 | SN A3NV11001-13098, SN A3NV13099-99999, SN A3NW11001-11248, SN A3NW11249-99999 |
| S750 | SN A3P211001-299999 |
| S770 | SN A39511001-99999, SN A3P411001-99999 |
| T550 | SN A7UJ11001-AJZV12276 |
| T590 | SN ALJU11001-999999, SN B37811001-999999, SN B3Z711001-999999 |
| T630 | SN A7PU11001-11663, SN A7PU11664-99999 |
| T650 | SN A3P012214-099999, SN A3P111242-199999 |
| T750 | SN ANKA11001-A99999 |
| T770 | SN A3P811001-899999, SN A3P911001-999999 |
| T870 | SN A3PG11001-99999 |
Frequently asked questions
What does Bobcat code A8105 mean?
It means the ACD/RACD attachment controller detected voltage on Output "B" (pin J1 B-7) when it had not commanded that output on, typically because that circuit or its return wire is shorted to battery voltage. The controller disables Output "B" in response.
What is the panel display number for A8105?
On the operator display, this code shows as 81-05.
Will my attachment stop working if A8105 sets?
Yes. Output "B" is disabled by the controller once this code sets, so whatever solenoid or function runs through that output will not operate until the issue is repaired and power is cycled.
Which Bobcat machines can show code A8105?
It applies to machines equipped with ACD/RACD attachment control, including the E35, E42, E45, E55 excavators and S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870 loaders.
How do I clear code A8105 after repair?
Cycle the key switch off and back on. No other clearing procedure is listed for this code.
Why does A8105 come and go instead of staying on?
Intermittent short-to-battery faults are often caused by loose connections, corrosion, or pins pushed back in a connector. If the fault is not active when you test, it may be hard to pin down until it recurs, so a thorough inspection of all connectors in the circuit is worthwhile even without an active fault.
Is A8105 a safety-critical code?
It is primarily an electrical fault affecting one attachment output circuit. It is not itself an engine or hydraulic safety shutdown, but if the disabled function is part of a safety-related attachment operation, treat the loss of that function with appropriate caution until repaired.