Turn Signal Flasher Relay | Honda CB175 / CB200 / CB350 / CB360 / CB450 / CB500 / CB550 / CB750
If your turn signals stopped flashing — staying on solid or not lighting at all — the flasher relay is the most common cause. This is the OEM-style thermal flasher relay, identical to the original factory unit Honda used across all 12V twins and fours from 1965 through 1978.
Why You Need This
The turn signal flasher relay is a thermal device — current flowing through a bimetallic strip heats it until it bends and breaks the circuit, creating the on-off flashing pattern. Over time, the internal contacts corrode or the bimetallic strip weakens — resulting in signals that stay on solid, flash erratically, or stop working entirely. Because the relay is grounded through its case, corrosion at the mounting point can also cause failures.
This replacement is identical to the original factory unit — same two-terminal design with spade connectors labeled B (battery) and L (load). It is designed for use with incandescent bulbs. If you are running LED turn signals, you need the electronic flasher relay instead — thermal flashers depend on the higher current draw of incandescent bulbs to generate enough heat to cycle.
Specifications
| Spec | Detail |
|---|
| Replaces OEM Parts | 38301-KJ6-743, 38300-292-670, 38301-KJ6-741, 38301-KJ6-742 |
| Fits Models | CB175 / CL175 / SL175 (1968–1973), CB200 / CL200 (1973–1976), CB250 / CL250, CB350 / CL350 / SL350 (1968–1973), CB360 / CL360 / CJ360 (1974–1977), CJ250T, CB450 / CL450 (1965–1974), CB500T (1975–1976), CB500K (1971–1973), CB550K / CB550F (1974–1978), CB750 (1969–1978) |
| Terminals | Two spade: B (battery/12V+) and L (load) |
| Grounding | Negative grounding through case — mounting point must be clean bare metal |
| Sold As | Single unit |
Note: This thermal flasher is designed for incandescent bulbs only. It will not reliably flash LED turn signals due to their lower current draw. For LED-compatible operation, use our electronic flasher relay.
Installation
Difficulty: Beginner
- Locate the flasher relay — it is typically mounted under the seat or inside the headlight bucket, depending on the model.
- Disconnect the two spade connectors from the old relay and remove it from its mounting bracket.
- Clean the mounting point to ensure bare metal contact — the relay grounds through its case.
- Mount the new relay and connect the wiring: black wire (12V+) goes to the B terminal, gray wire goes to the L terminal.
- Turn the key on and test both turn signals.
Troubleshooting tip: If the new relay does not flash, check the connectors on the wiring harness for corrosion. Also inspect the switch in the left-hand control to ensure it is making proper contact.
Our turn signal circuit troubleshooting video covers how the thermal flasher relay works, how to diagnose failures, and the complete turn signal wiring circuit.
Frequently Asked Questions
Will this flasher relay work with LED turn signals?
No. This is a thermal flasher that relies on the higher current draw of incandescent bulbs to heat the bimetallic strip and create the flash cycle. LED bulbs draw much less current, so the relay will not cycle — your signals will stay on solid or not light at all. Use our electronic flasher relay for LED turn signals.
My turn signals flash on one side but not the other. Is the relay bad?
Probably not. If the relay flashes on one side, it is working. A one-side failure usually points to a burned-out bulb, a bad ground at the signal housing, or a faulty connection in the left-hand control switch. Check the bulbs and wiring before replacing the relay.
Where is the flasher relay located on my bike?
On most Honda twins, the flasher relay is mounted under the seat near the battery or inside the headlight bucket. Look for a small cylindrical or rectangular unit with two spade terminals labeled B and L.
What is the difference between this relay and the electronic flasher relay?
This is the OEM-style thermal flasher — it uses heat from current flow to cycle on and off, and only works with incandescent bulbs. The electronic flasher relay uses a solid-state circuit that works with both incandescent and LED bulbs regardless of current draw.
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Last updated: March 2026
