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Old 07-17-2018, 10:07 PM   #1
ttrousdell
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Check panel lit but brake lights functioning

My brake lights are in good working order but the check panel continues to stay lit for a brake light fault. Any ideas?
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Old 07-17-2018, 10:17 PM   #2
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Check the side marker lights in the bumper, they can throw the light for the brake light circuit. If they’re all working, pull all the bulbs, clean them and the housings, and apply dielectric grease to everything.
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Old 07-17-2018, 10:23 PM   #3
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That’s prob it. One of my side marker lights has been out for a while. Will change and see if that does the trick.
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Old 07-18-2018, 04:56 AM   #4
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Also make sure you're using nickel bases on the bulbs (silver color). They have a different resistance than brass and can mess with the check system.
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Old 07-18-2018, 03:00 PM   #5
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The transistors that control the LED's can get stuck after 30 years, so keep that in mind, the check panel system can start to fail
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Old 07-18-2018, 03:58 PM   #6
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yer my check lights are all over the place. I'm considering cutting power to it. The brake light one is always on and the coolant one comes and goes. Wouldn't be an issue if you didn't start flashing check on the dash on startup.
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Old 07-18-2018, 07:27 PM   #7
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Side markers all functioning, bulbs all nickel base and contacts cleaned, check panel swapped from another car. problem persists. I have heard the brake light switch can fail. Will look at that next.
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Old 07-23-2018, 11:20 AM   #8
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If the switch failed then the lights wouldn't come on. Did you check the 3rd brake light? It has its own internal check relay that can be problematic.
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Old 08-02-2018, 11:23 AM   #9
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You might have issues with the check control relay itself. Poor contact, cold solder joint cracks, or worn out reed relays.



I suggest you jumper across the brake light check relays (they're the two with less wire turns), and see if the check light persists. If so, then you have issues elsewhere in the check system.

The brake light check system is extremely finicky. If there is even the slightest delay, or the current drawn is even slightly too low, the light will come on. The reed relays are seriously underwound in my view by default. There is less than 100mA of current margin on them.
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