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Old 04-24-2016, 02:42 AM   #1
Bru
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Default dash BRAKE light weirdness, won't go off, solved

About a week ago I noticed my BRAKE light was glowing red all the time but not as bright as when the handle was lifted. In fact, when I lifted the handle it got normal bright. The BRAKE light has two functions: it lights when the handle is lifted, and it lights when the brake fluid reservoir is low. The normal operation is for the light to be on until the engine starts and then it should go out, provided the handle is down. I checked the function of the handle switch and the brake fluid reservoir switch according to the Toyota dealership manual. The e brake handle switch checked out ok. The float switch with the float down measured 7 Ohms instead of infinity or no continuity. With the float up, it was about 100 Ohms instead of about 0 Ohms resistance using a sensitive needle Ohm meter. I suspect the float switch has gone bad since when I unplug it the BRAKE light goes out which simulates the normal open condition when there is enough fluid. Jumping the harness side of the plug made the light come on normal bright. A new res cover for a 86-92 Supra or 91-95 MR2 is ~$91. Part number 84460-12070. I hope eBay Mike in KY has a used one. For now its unplugged. A whole new master cylinder with the cap for a ABS brake system is ~$200.

Last edited by Bru; 04-25-2016 at 11:34 PM.
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Old 04-26-2016, 01:19 AM   #2
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If you're handy, and I know you are, the sensor is just a magnetic reed switch inside the plastic shaft. You could try replacing that by itself before investing more money.
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Last edited by cre; 04-26-2016 at 01:21 AM.
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Old 04-26-2016, 03:11 PM   #3
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Thanks for the info Cre. I had that float/vent stalk pulled out from the cap after I took the leads out of plug on the other end. It looked sealed up with epoxy and I was not ready to do surgery on it. I guess I have nothing to lose now by taking a peek to fix or replace it with a similar switch if one can be found. Mabie a parts yard donor switch from a 80s Celica or Corolla.
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