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Nov 20, 2025 - 09:44 AM
The 1996 K1500 uses a dedicated Turn Signal/Hazard Flasher (it is a single unit for both). The constant-on (not blinking) symptom is the classic failure mode for this electromechanical flasher unit. Even though you checked "relays," this part is different and is often overlooked.
• Location: The flasher unit is typically located under the dash on the driver's side, often mounted in the convenience center (relay block) near the emergency brake pedal. You may need to remove the lower dash panel to see it clearly.
• Appearance: It is usually a small, round or rectangular 3-pin thermal flasher.
• Action: Replace this flasher unit immediately. They are inexpensive (often under $20) and are the most common source of the "lights on, but won't flash" problem.
Quick note, if you installed any LED bulbs, your gonna need an electronic flasher like a "Novita EP29" to handle that low resistance of the LEDs, otherwise they will either not flash or hyper flash. But if you have the regular bulbs stick with the thermal flasher, since the lights are staying on, but an electronic flasher, might be a good upgrade anyhow. Inspect the multi function switch connector. Since you put in a brand new MFS the issue could be at the connection point. The fact that the lights are constantly lit, it suggest a permanent pass to ground or power, bypassing the flasher/blinking mechanism. Disconnect the wiring harness that plugs into the back of your new MFS. Use a flashlight or and magnifying glass to look at the pins inside the connector on the wiring side, that's an important note, (on the wiring side). Look for any pins that are pushed out of the connector housing, bent, or corroded. A poor connection here can easily cause the fault that you're having essentially bridging two Contacts together. Check for a wiring short (their are specific wire colors). If replacing the flasher unit doesn't fix it, you need to look for a short along the wires that carry the power to the lights. The hazard lights are powered by the flasher, which is then connected to the MFS. You're 96 GMT400, the wires that carry the flashing signal out to the lights, are typically light blue, which is the left side and dark blue, which is the right side trace the light blue, and the dark blue wires coming from the steering column harness. Look for anywhere they might be pinched or have the insulation rubbed through, causing them to touch constant power, like a red wire, or a good ground black wire. This can happen with a harness passing through the firewall, or is tied near the steering column, by a zip strip or somethihg. The flasher unit on that truck uses a dedicated, turn signal/hazard flasher. It's like an all in one. The "constant on" symptom is the classic failure mode for the flasher unit. Even though you checked relays, this part is different and it's often overlooked. The flasher unit is typically located under the dash on the driver side, mounted in the convenience center, a relay block near the emergency brake pedal, again you might need to remove the lower dash panel to see it. And again just telling you it's a three pin thermal, flasher, replace that flasher immediately because that's probably the issue. If that doesn't fix it, reply back to this same thread and I'm following it, so I'll chime in again. Electrical happeEljefebe my specialty, I'm a Harley Davidson technician and i know wiring and this truck. My name is (Eljefe) Jeff, lol nice to meet you and i hope this helps.
Source: I am a certified Harley Davidson tech and I happen to know this truck. had one growing up
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