Bobcat H4503 (45-03) Fault Code: Right Blinker Error Off
Also shown on the panel as 45-03
Right Blinker Error Off · ai-assisted, editor-reviewed · Last updated 2026-07-13
TL;DR
H4503 (panel code 45-03) sets when the auxiliary controller commands the right blinker relay but does not detect voltage on signal wire 6520. It points to a wiring, relay, or controller problem in the right turn signal circuit, not an engine or hydraulic fault.
Low severity. This code affects a signaling function, not machine performance or safety systems that control movement or lifting. It should still be fixed before road or jobsite travel where turn signals are required for other workers and traffic to see your intentions.
What does Bobcat error code H4503 mean?
H4503 is a Bobcat auxiliary controller fault tied specifically to the right blinker circuit. The controller sends a command to energize the right blinker relay whenever the operator activates the right blinker switch, which is mounted on the right grip. The controller expects to see voltage return on signal wire 6520 confirming the relay switched on.
When that voltage isn't detected, the controller logs H4503. This tells you the command went out but the expected electrical response didn't come back, which usually means a break, short, or bad connection somewhere between the switch, the controller, and the relay.
This is a signal-circuit issue, not a structural or hydraulic problem. The machine will still drive and operate normally, but the right blinker may not function, which is a real safety and legal concern on roads or shared jobsites.
Common causes of H4503
- Signal wire 6520 shorted to ground
- Failed or sticking right blinker relay
- Fault in the auxiliary controller itself
- Moisture, corrosion, or pushed-back pins in the auxiliary controller connectors, the AWS horn/blinker harness, or the mainframe harness
- Intermittent causes that may not show up during testing, including loose connections, corrosion, pushed-back pins, the controller, the wire harness, or a combination of these problems
How to troubleshoot Bobcat H4503: first checks
- With the key switch or run/enter switch on, activate the right blinker switch on the right grip and watch for the relay clicking or listen for it energizing
- Inspect the auxiliary controller connectors for moisture, corrosion, or pins that have been pushed back out of their sockets
- Check the AWS horn/blinker harness and mainframe harness connectors along the run to the right blinker relay for the same issues
- Test signal wire 6520 for a short to ground using a multimeter with the harness disconnected from the controller
- Swap or bench test the right blinker relay if wiring and connectors check out clean
- If the code appears intermittently and isn't present during testing, recheck all connectors under vibration or after operating conditions that may flex the harness
How the code clears
Once the repair is complete, clear the code by cycling power (turning the key switch or run/enter switch off, then back on). No separate clearing procedure is listed beyond the power cycle.
Affected models and serial ranges
H4503 appears in our records across 16 Bobcat models. Match your machine by model and serial number.
| Model | Serial ranges |
|---|---|
| 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 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, SN A3PH11001-99999 |
Frequently asked questions
What does Bobcat code H4503 mean?
It means the auxiliary controller commanded the right blinker relay to turn on but did not detect voltage on signal wire 6520, the wire that confirms the relay activated.
Is H4503 dangerous to keep operating with?
It won't affect engine performance, hydraulics, or lifting, but a non-working right blinker is a real safety issue on roads or around other equipment and workers. Repair it before road travel.
Where is the right blinker switch located?
On the right grip of the machine. Activating it sends a command from that switch to the auxiliary controller, which then energizes the right blinker relay.
What usually causes H4503?
Common causes include signal wire 6520 shorted to ground, a failed right blinker relay, a fault in the auxiliary controller, or moisture and corrosion in the connectors along the auxiliary controller, AWS horn/blinker harness, or mainframe harness.
Why does the code come and go instead of staying on?
Intermittent H4503 codes are usually caused by loose connections, corrosion, or pushed-back pins that only cause a problem under certain conditions like vibration or moisture. If the code isn't active during testing, the fault may not show up right away.
How do I clear H4503 after I fix it?
Cycle the key switch or run/enter switch off and back on. That is the only clearing step listed for this code.
Which Bobcat models can show H4503?
It applies across S510, S530, S550, S570, S590, S630, S650, S750, S770, T550, T590, T630, T650, T750, T770, and T870 models.