Turn signal Flashers

[broncow38]

Ive replaced three flashers. They work for a little bit then glow and don't flash. I've checked grounds and power. What would cause this. Sometimes they work other times just a bulb glow. Hmmmm.

 

[Dusty]

I was curious about your question so I asked ChatGPT, as mine occasionally does this too. Here's how that went.

What would cause a flasher to fail on a 1975 Bronco? I’ve replaced it three times. They work for a short while then glow and don’t flash. Grounds and power to the flasher have been checked and seem good. What would cause this? Sometimes they work and other times the signal just glows steadily.​

ChatGPT said:​

You're chasing an electrical gremlin — classic old Bronco stuff. If your flasher is burning out or failing after a short time and the signals are glowing steady instead of flashing, even after replacing it multiple times, here are the most likely causes and things to check:

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1. Wrong Type of Flasher​

• Check if you're using the correct type of flasher for the 1975 Bronco. There are two common types:
  
  • Thermal flashers (which depend on resistance/load to function correctly)
  • Electronic flashers (less sensitive to load but can still be picky)
• If you’ve installed LED bulbs, a thermal flasher won’t work right. It needs the load of old-school incandescent bulbs.
• If still running incandescent bulbs, make sure the flasher is rated for the current draw of your bulbs (usually 2 bulbs per side).

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2. Excessive Load or Short in the Circuit​

• Corroded sockets, pinched wires, or aftermarket add-ons (like a trailer harness) can cause extra draw or intermittent shorts.
• A short to ground or a partially shorted bulb socket can cause the flasher to overheat and fail.
• Pull the bulbs and check for green corrosion, loose socket contacts, or melted connectors.

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3. Bad Turn Signal Switch (in the column)​

• A common and sneaky failure point.
• The internal contacts can get dirty or worn, causing bad connections that confuse the flasher.
• This could explain why it sometimes works, sometimes doesn’t, and sometimes just glows.

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4. Poor Grounds — Even If They "Seem" Good​

• Grounds can be visually fine but electrically poor. Run a temporary jumper wire from the bulb socket to a known good ground and test again.
• Make sure the tail lights and front signal housings have solid metal-to-metal contact with the body/frame.

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5. Overheating Flasher Location​

• If the flasher is in a spot with poor airflow or near a heat source, it could fail prematurely.
• Some aftermarket flashers are junk — try a heavy-duty flasher from a brand like Novita or Wagner.

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Bonus Test: Bench Check​

1. Take the old flasher and a couple of bulbs wired in parallel on the bench.
2. Feed it power and ground and watch what it does. If it fails quickly in this simple setup, it’s just a bad flasher.

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Want to walk through how your wiring is set up or what flasher you’re using exactly? I can help you double-check compatibility too.