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3 of 4 brake lights always on after manual conversion, at a lost wtf is going on

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Posted (edited)

just got around to doing an auto to manual swap in an r34 gt to gtt manual box, auto dash shows N in neutral and reverse in reverse lights beeps, speed, rpm temps etc all work. 

BUT now brake lights semi work and don't work. The furthest left light and the high brake lamp work, the other 3 are permanently on, no idea if these 3 run off a different circuit? Makes no sense but ill probs try anything at this point lol.

Edited by hugh jaynous
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It is not directly caused by the swap. You may well have broken something during the swap, but the swap itself is  not the cause.

The most likely cause is the brake pedal switch. You would have had to be stuffing around in the footwell to fit the clutch pedal, so....there's how you break something. The pedal switch will be stuck on, feeding all 4 lights. The reason one of them is not working will be because of a broken globe, or a faulty earth at that light, not because of some magical thing capable of creating a single fault that makes only 3 out of 4 come on.

The brake light circuit is about the simplest circuit on the car. Break out the wiring diagram and a multimeter and start finding the fault.

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i guess to clarify the explanation a bit, all the lights light up, but only one brake light + high lamp is properly functioning ie; when off the brake pedal and the pedal switch is fully pressed down in contact with the pedal that one light is dimmed while the other 3 show no change as if im still stepping on the brakes. I'll try to poke around with a multimeter now, but if by some stroke of genius there's some other thing possible missed im all ears, thanks!

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Sorry, I should have read the OP more thoroughly. Sounds like you could be backfeeding the circuit from somewhere, which shouldn't be an easy thing to do if the wiring is original and unbastardised. But because it's a 25 year old car and you've just done a modification that includes messing with the wiring loom, it is actually best to describe it as bastardised and proceed accordingly. Proceeding accordingly would be to presume that your fault is unique to your equipment and diagnosis from afar/past experience will be unlikely to just give you the exact thing to look for. It always turns out to be something f**ked up that was completely unexpected.

The method is still the same. Grab wiring diagram and multimeter, screw on the thinking cap, and start diagnosing where power is (and should be and shouldn't be) and where it isn't (and should be and shouldn't be), with the switch open, closed, globes in and out, at earth points, etc, etc.

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On 13/05/2022 at 12:59 AM, GTSBoy said:

Sorry, I should have read the OP more thoroughly. Sounds like you could be backfeeding the circuit from somewhere, which shouldn't be an easy thing to do if the wiring is original and unbastardised.

ah....i never thought about this, since i just snipped the two auto connectors and spliced the 3 wires to neutral/reverse/inhib and then taped the other cables back without making sure they didn't touch another cable, potentially some of those cables are actually contacting each other now.

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