BU Light ? - Team Camaro Tech
Electrical & Wiring Troubleshooting electrical.

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post #1 of 11 (permalink) Old Apr 15th, 19, 06:08 PM Thread Starter
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BU Light ?

67

what would be the best place to look, beyond fuse, to determine why BU lights don't work. They did.

BU switch on shifter?

is it under shift plate or under car?
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post #2 of 11 (permalink) Old Apr 15th, 19, 07:15 PM
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Re: BU Light ?

Harness wire colors are pink (ignition) and green. If you have already tried the bulbs, you can work backwards starting at the rear light/dash harness connector and then to the dash harness (in between the gauge connector and heater area). If you apply 12v to the green wire, you “should” get a light in the back if the wiring is good. Did you verify the bulb socket in the back is good? You could also check the bulb for 12v when the circuit is “energized”. Do you have an auto, manual? Which dash harness do you have? If you have an auto, look for the pink/green wires on shifter. Manual has switch on the trans.

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post #3 of 11 (permalink) Old Apr 15th, 19, 07:19 PM
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Re: BU Light ?

If stick pull the plug on the firewall and jump the connector. If they light the answer is under the car.
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post #4 of 11 (permalink) Old Apr 16th, 19, 07:03 AM Thread Starter
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Re: BU Light ?

It's a automatic, powerglide, floor shift

They did work before so my thought is the BU switch may be at fault.....although I will pull both bulbs to see if they simultaneously burned out

All fuses are good under dash

Is this BU switch under the shift plate inside console or on the transmission under car?

stock wiring harness

BU light circuit is independent from headlight switch, correct?
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post #5 of 11 (permalink) Old Apr 16th, 19, 07:29 AM
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Re: BU Light ?

The switch is accessible by pulling the shift plate.
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Al

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post #6 of 11 (permalink) Old Apr 16th, 19, 07:41 AM Thread Starter
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Re: BU Light ?

Quote:
Originally Posted by allanjs View Post
The switch is accessible by pulling the shift plate.
thanks Al


My thought is the switch is the most likely suspect given the BU lights had been working so will check that first before back probing wiring from the rear

I recently installed gauges but did not disturb any existing wiring under dash.....that I recall anyway
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post #7 of 11 (permalink) Old Apr 16th, 19, 08:25 AM
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Re: BU Light ?

Roger, I'm not sure if your fuse block is the same as mine due to your car being
an original console car but my fuse block is labeled back up - gauges. So I would
say the back up lights are separate from the headlight circuit. Also I believe the
back up circuit is connected at the harmonica connector (pink wire).

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post #8 of 11 (permalink) Old Apr 17th, 19, 04:04 AM
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Re: BU Light ?

I went through this a few months back, having to install a missing neutral safety switch on my floor shifter (automatic transmission). If you remove the 4 screws that hold down the two half pieces that surround the shifter's shaft, you should be able to see the neutral safety switch to the drivers side of the shifter's base shaft. There will be four wires connected to this switch; two large guage purple wires, which are for the starter voltage, allowing the engine to start in Park or neutral only. Then there will be a smaller red and green wire; these are used for the reverse lights. The red is 12 volts, and the green wire runs (eventually) to the back tail light housings to provide power to the reverse light bulbs.

With the key in the "run" position (no need to start the engine), verify there is 12 volts at the red wire. If so, move to next step, which is to put the gear selector to the "R" (reverse) selection. The green wire should have 12 volts now. If not, wiggle the shifter front to back a bit to see if the neutral safety switch contacts are dirty (inside of the switch). If you get 12 volts at the green wire at the nuetral safety switch location, the fault is after the switch. If you don't see 12 volts at the red wire, fault is from red wire to fuse panel. If you have 12 volts at red lead, but not at green lead with selector in reverse, and ignition key in the run position, then the neutral safety switch is suspect. This switch can be removed, and there are 4 tabs that can be carefully bent back to allow you access to the copper contacts inside the switch. Clean them with some fine sandpaper, apply a smear of grease on the copper, then reinstall its cover, and use a volt/ohm meter to check for continuity at the two contacts that are for the reverse light wire connections, and also the starter connectors. Reinstall the switch. Test again.

If the neutral safety switch checks out good (12 volts at green wire when the shifter is in reverse and ignition key is in the run position), then fault is within the green wire to rear of tail light assemblies. Check that the reverse bulbs are good, and that you detect a good ground at these two bulb sockets. The 67 tail light assemblies obtain their ground using 4 "bumps" of the tail light assemblies making good contact with the body. You would have to remove each tail light assembly from the car to see these. Since the other rear lights are working (brake, turn signal, and running lights), the ground is assumed good though at this location.

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post #9 of 11 (permalink) Old Apr 17th, 19, 07:17 AM Thread Starter
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Re: BU Light ?

Bucko

Thanks for the very detailed 411......I did just remember (duh) the tail lights were removed by paint shop last month to do some touch up on the rear panel....I need to look closer in that area and if that checks out...go to the shifter switch

Your detailed red/green wire function will greatly assist in this.

yes, on closer inspection, I did see the fuse panel labeled "BU". That fuse is good
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post #10 of 11 (permalink) Old Apr 17th, 19, 09:15 AM
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Re: BU Light ?

Quote:
Originally Posted by SoCal805 View Post
Bucko

Thanks for the very detailed 411......I did just remember (duh) the tail lights were removed by paint shop last month to do some touch up on the rear panel....I need to look closer in that area and if that checks out...go to the shifter switch

Your detailed red/green wire function will greatly assist in this.

yes, on closer inspection, I did see the fuse panel labeled "BU". That fuse is good
Also, if the neutral safety switch was replaced with an afermarket replacement, the two reverse lights may be both green on the switches side. No big deal, and if you still have the factory plug from the harness to the switch, it will connect right up.

My 67 was originally a column shift, and when one of its previous owners added a correct factory floor shifter, they left off the neutral safety switch. They simply connected the two purple wires together by the steering column (where a column shift neutral safety switch was located), and left the red/green wires for the reverse lights dangling with black tape unconnected. I created a harness to route these wires to the center console (yea, I could have bought one), and connected spade connectors to plug into the switches connector.

Never argue with an idiot; they'll only drag you down to their level, then beat you with experience.
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post #11 of 11 (permalink) Old Apr 19th, 19, 07:43 AM Thread Starter
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Re: BU Light ?

Well apologies as I had a "DOH" moment and posted without first checking the bulbs themselves. Both burnt out which I initially assumed "no way both simultaneously burnt out" so assumed switch or wiring. They were the 87 bulbs which now are the 1156 so I assume they were in there a loooong time.

BU lights work now :-)
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