 Brain Trust Help needed on Parking Brake Light, Parking Brake Light Always on...... |
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| Gatornapper |
 Jul 4 2025, 07:40 PM
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#1
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Senior Member  Group: Members Posts: 1,274 Joined: 22-September 17 From: Woods west of Richmond, VA Member No.: 21,449 Region Association: South East States 
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Once again need the help of the great 914 Brain Trust here........
My Parking Brake Light stays on all the time. The switch is fairly new and it is functioning properly. Disconnecting the brown (ground) wire to the switch, it has no continuity or resistance to ground. So it is not "grounded out" somewhere. I see in my great 914 electrical schematic of the ground circuit for the switch and light that there are two diodes in the circuit. I am guessing that one of them failed. Can anyone tell me where these two diodes are located? Or where else the problem might be? As always, TIA, GN |
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| jim_hoyland |
Jul 4 2025, 08:41 PM
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#2
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Get that VIN ? Group: Members Posts: 9,808 Joined: 1-May 03 From: Sunset Beach, CA Member No.: 643 Region Association: Southern California
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MC ?
I just went through this… (IMG:style_emoticons/default/smile.gif) |
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| Jamie |
Jul 5 2025, 09:03 AM
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Senior Member Group: Members Posts: 1,126 Joined: 13-October 04 From: Georgetown,KY Member No.: 2,939 Region Association: South East States
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QUOTE(jim_hoyland @ Jul 4 2025, 06:41 PM)  I'm also trying to troubleshoot the flashing red instrument light. Didn't locate the brake switch illustrated in the shop manuals, and have no good access down beside the seat. Have pushed the MC pin in several times with no effect, no leaks, and brakes are working just fine. Don't know what to try next? (IMG:style_emoticons/default/blink.gif) |
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| Literati914 |
Jul 5 2025, 10:01 AM
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#4
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Senior Member Group: Members Posts: 1,999 Joined: 16-November 06 From: Dallas, TX Member No.: 7,222 Region Association: Southwest Region |
@Gatornapper - if you pull the combo gauge, you'll see the two diodes... (your model may be different, but) on my '72 there are two diodes going to the e-brake/MC flashing bulb - one diode is looped over from the generator bulb and the other diode is where two Brown/White wires are combined (these are e-brake and 'fasten seat belt dash light').
But before looking in to those - pull the other single Brown/White wire from the bulb and see if the flashing stops.. that's the wire from the MC, and you can isolate the problem that way. |
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| Gatornapper |
Jul 5 2025, 10:47 AM
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#5
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Senior Member Group: Members Posts: 1,274 Joined: 22-September 17 From: Woods west of Richmond, VA Member No.: 21,449 Region Association: South East States
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Ah yes! On my schematic it does look like one diode is next to bulb. Other one seems to be near the switch but I don't see one there......
Great suggestion, I will do this. THANK YOU! Will let you know. What is "MC"? GN QUOTE(Literati914 @ Jul 5 2025, 10:01 AM) @Gatornapper - if you pull the combo gauge, you'll see the two diodes... (your model may be different, but) on my '72 there are two diodes going to the e-brake/MC flashing bulb - one is looped over from the generator bulb and the other is where two Brown/White wires are combined (these are e-brake and 'fasten seat belt dash light'). But before looking in to those - pull the other single Brown/White wire from the bulb and see if the flashing stops.. that's the wire from the MC, and you can isolate the problem that way. |
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| BillC |
Jul 5 2025, 11:05 AM
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#6
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Senior Member Group: Members Posts: 674 Joined: 24-April 15 From: Silver Spring, MD Member No.: 18,667 Region Association: MidAtlantic Region
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QUOTE(Gatornapper @ Jul 5 2025, 12:47 PM) What is "MC"? "MC" is short for Master Cylinder. |
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| Literati914 |
Jul 5 2025, 12:10 PM
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#7
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Senior Member Group: Members Posts: 1,999 Joined: 16-November 06 From: Dallas, TX Member No.: 7,222 Region Association: Southwest Region |
QUOTE(BillC @ Jul 5 2025, 12:05 PM) QUOTE(Gatornapper @ Jul 5 2025, 12:47 PM) What is "MC"? "MC" is short for Master Cylinder. Yea that flashing bulb is not just the E-brake warning light - it's also the Master Cylinder warning light. So the non-stop flashing could be from either circuits going to the bulb. You can pull one at a time and see if the light stops blinking. Alternately you could pull the wires off the MC itself. |
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| Superhawk996 |
Jul 5 2025, 12:23 PM
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#8
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914 Guru Group: Members Posts: 7,212 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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Simplified schematic from Spoke
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| Superhawk996 |
Jul 5 2025, 12:25 PM
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#9
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914 Guru Group: Members Posts: 7,212 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch
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QUOTE(Jamie @ Jul 5 2025, 11:03 AM) I'm also trying to troubleshoot the flashing red instrument light. Didn't locate the brake switch illustrated in the shop manuals, and have no good access down beside the seat. Have pushed the MC pin in several times with no effect, no leaks, and brakes are working just fine. Don't know what to try next? (IMG:style_emoticons/default/blink.gif) Troubleshoot with Multimeter using Spokes schematic above |
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