View Full Version : Wonky Brake Light
Trying to solve one lighting gremlin prior to putting the body on.
The brake lights illuminate when the brake pedal is applied with the headlight switch off, but when the headlight switch is on or at the parking light (first) detent, only the left brake light illuminates when the brake pedal is applied. This is regardless of key position.
I'm using the RF harness with the vintage gauges and followed the wiring diagram with the following exceptions:
- I moved the orange/purple wire to the forward spades on the brake safety switch (as noted from other posts about the instructions being wrong)
- Using a DPST toggle switch for the hazards
- Using the RT turn stalk - but only for a turn signal; no horn, flash to pass, etc
- Using a RF rotary wiper switch
Other than the wonky brake light, everything else works in the various switch combinations. No issues either with the courtesy lights, dash lights, dash indicators, stereo, etc.
I have grounds at all four corners for the lights in addition to the main RF harness ground wire.
I've been checking my grounds, but is there anything else that could be the likely issue?
I'm stumped. Thanks for the help.
Big Blocker
07-21-2019, 06:25 PM
Pull all the bulbs and then re-nstall them one-at-a-time . . . The F5 supplied sockets are known to be "loose" and a bulb can be inserted 180° off, causing a short between the tail light circuit and the brake circuit (two different circuits).
Doc
Pull all the bulbs and then re-nstall them one-at-a-time . . . The F5 supplied sockets are known to be "loose" and a bulb can be inserted 180° off, causing a short between the tail light circuit and the brake circuit (two different circuits).
Doc
Thanks Doc. Gave it a shot but no luck. I also switched bulbs but got the same wonky behavior.
You can get some strange light behavior when there is a loose or bad ground. I did weatherpack connectors for all my lights and found out the hard way that some of my crimped pins were done poorly the first time around.
boat737
07-22-2019, 10:43 AM
Sounds like there may be a wire crossed at one of the brake/parking lights (maybe even the front parking/turn lights). Double check that the parking circuit wires are to the parking (low intensity) bulb contacts, the brake circuit wires are to the brake (high intensity) bulb contacts, and that the ground circuit wires are to the socket grounds. You can do this by unplugging all the light fixtures, and checking one at a time (and unplug it again before testing the next fixture.). Start with the right one first since that is the one problem light. Use a test light or Power Probe.
Do the turn signals operate properly (with and without the headlight sw. on)? And do they work properly with the brake pedal pushed? Do the flashers work properly (with and with out headlight sw on)? Do the flashers work properly with the brake pedal pushed?
Do the turn signals operate properly (with and without the headlight sw. on)? And do they work properly with the brake pedal pushed? Do the flashers work properly (with and with out headlight sw on)? Do the flashers work properly with the brake pedal pushed?
Yes. Everything else works.
Ducky2009
07-22-2019, 11:08 AM
I had a front light issue. My problem turned out to be in the factory harness assemble. Two of the wires at the factory plug were reversed. A tan wire was plugged into a green wire and vice-versa. Took me HOURS to realize it wasn't my wiring, but the factories.
I think the problem is the particular rear light harness. I swapped the white (Rt turn) and purple (brake) wires connecting the green (bright element) wires, and now the brake lights work in all switch configurations, but the right rear turn light only flashes when the headlight switch is selected off. :confused:
Front right turn light is fine in all switch configurations.
A multimeter on the white (rt rear turn) wire at the end of the rear harness confirmed that I have 12 dropping to about 3 or so volts during flashes when the right turn switch is selected, regardless of headlight switch configuration, leading me to think the problem is the light harness.
Next step is to swap tail light harnesses to see if the issue follows the harness.
More to come...
I had a front light issue. My problem turned out to be in the factory harness assemble. Two of the wires at the factory plug were reversed. A tan wire was plugged into a green wire and vice-versa. Took me HOURS to realize it wasn't my wiring, but the factories.
Yup. That was EXACTLY the issue here - the green wire and red/yellow wires were wrong in the factory harness. Swapped them with the white and tan wires at the rear harness and it was Christmas in July. ;):o:cool:
So, the issue was the factory rear light harness - the green wire (to power the bright filament in the bulb) and the red/yellow wire (to power the low filament in the bulb) were reversed in the harness. In this configuration, the brake light, and later the turn signal were powering the low filament instead of the bright one, but it wasn't evident because when the headlight switch was on, the bright filament was powered and washed out the flashing low filament on that one harness. So it appeared as if the rear right brake light/turn lights weren't working.
It became obvious with the tail light lens cover off though - the lower filament in the bulb is the bright filament for brakes/turn signal, and the upper filament is for lights. I noticed that with the headlights selected on, only the suspect harness had the brighter filament illuminated. Conversely, when the right turn signal was selected, the lower filament illuminated and flashed, whereas the brighter filament illuminated for a left turn in the other harness.
After swapping the tail light harness wires, all was good, and I lived happily ever after. The end.