Bobcat A8506 (85-06) Fault Code: ACD/RACD Output “F” Short to Ground
Also shown on the panel as 85-06 · Also called ACD Output ‘F’ Short to Ground, ACD/RACD Output “F” Short to Ground
ACD/RACD Output “F” Short to Ground · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
A8506 (panel form 85-06) sets when the Bobcat ACD/RACD controller commands output "F" but does not detect voltage on output "F" (controller pin J1 B-19) or its return wire (controller pin J1 A-18). The controller disables output "F" when this happens.
Medium severity. Output "F" is disabled once the code sets, so whatever attachment function that output drives will stop working. This is not an engine-damage or immediate-shutdown fault, but it does take away a commanded function, so it should be diagnosed before relying on that attachment circuit again.
What does Bobcat error code A8506 mean?
A8506 is set by the Attachment Control Device / Remote Attachment Control Device (ACD/RACD) controller on many Bobcat skid-steer, compact track, and compact excavator models. The controller sends a command to energize output "F" and expects to see voltage return on the paired return wire. When it commands the output but does not see that voltage, it flags A8506.
Once the code is active, the controller disables output "F" as a protective measure. Practically, this means whatever attachment function or solenoid wired to output "F" will stop responding until the fault is found and cleared.
This code points to an electrical short to ground somewhere in the output "F" circuit, in the solenoid it feeds, or in the controller itself, rather than a hydraulic or mechanical failure.
Common causes of A8506
- Output "F" wire (controller pin J1 B-19) or its return wire (controller pin J1 A-18) shorted to ground.
- Failed or shorted output "F" solenoid.
- Fault inside the ACD/RACD controller.
- Moisture, corrosion, or pushed-back pins in the ACD/RACD controller connectors, the mainframe harness, the attachment control harness, or the output "F" solenoid connector.
- Intermittent condition: if the code is not active at the time of testing, the root cause may not be found right away. Probable causes in this case include loose connections, corrosion, pushed-back pins, the controller itself, the wire harness, or a combination of these.
How to troubleshoot Bobcat A8506: first checks
- Confirm the key switch is in the run/enter position, since this is the condition required for the code to be active, then check whether A8506 is currently present or only stored in history.
- Inspect the ACD/RACD controller connectors and the attachment control harness connectors for moisture, corrosion, or pushed-back pins.
- Trace output "F" wiring at controller pin J1 B-19 and the return wire at controller pin J1 A-18, checking for chafing, pinching, or contact with ground anywhere along the harness and at the attachment interface.
- Inspect the output "F" solenoid and its connector for a shorted coil or damaged wiring.
- If the code is not currently active, wiggle-test connectors and harness sections while watching for the code to reappear, since an intermittent short may only show up under vibration or movement.
- Check the mainframe harness routing for wear points where it could rub through insulation and short to the frame.
How the code clears
Once the wiring, solenoid, connector, or controller issue is repaired, cycle the key power to clear the code. No separate clearing procedure beyond a power cycle is listed for A8506.
Affected models and serial ranges
A8506 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 A8506 mean?
It means the ACD/RACD controller commanded output "F" but did not detect the expected voltage on that output (controller pin J1 B-19) or its return wire (controller pin J1 A-18), so it assumes a short to ground and disables output "F".
What is output "F" on a Bobcat attachment control system?
Output "F" is one of the commanded outputs from the ACD/RACD controller, typically wired to an attachment solenoid. When A8506 sets, that specific output is disabled until the fault is fixed and power is cycled.
Will A8506 stop my attachment from working?
Yes. The controller disables output "F" as soon as the code sets, so any attachment function tied to that output will not respond until the short is found and repaired.
How do I clear code A8506 after repair?
Cycle the key power. No other reset procedure is listed for this code.
Why does A8506 keep coming back even after I check everything?
If the code is intermittent and not active during testing, the cause may not show up right away. Loose connections, corrosion, pushed-back pins, the controller, or the wire harness (or a combination) are the likely suspects, so a wiggle test on connectors and harness runs while watching for the code to reset is often needed.
Which Bobcat machines use this ACD/RACD code?
A8506 applies across a wide range of Bobcat models including the E35, E42, E45, E55 excavators and the S510, S530, S550, S570, S590, S630, S650, S750, S770 skid-steers along with the T550, T590, T630, T650, T750, T770, T870 compact track loaders.
Is A8506 a hydraulic problem?
No. A8506 is an electrical fault, a short to ground on output "F" or its return wire, on the solenoid it feeds, or inside the controller itself. It is not caused by hydraulic pressure or flow issues.