Mk5 Turn signal engaged but no blinking lights.

[Pete&Scott]

Testing my wiring and have some issues. Front and rear running/tail lights work when pulling the hazard button. No turn signals on front or back when I engage the turn signal switch on the steering wheel. When the running lights are on, and I pull the hazard button, the tail or front lights do not blink. Any suggestions on why the turn signals are not coming on?

The left/driver's side taillight does not come on when I turn on the running lights. I get power on the tan wire at the rear harness connector at the dash, and I am guessing the tan wire feeds both tailights and splits at the Y in the harness, since only one tan wire at the harness connector. I will dig into the harness and see if the tan wire to the left was not properly spliced, unless anyone has any other suggestions. Both lights work when connected to the right side.
225413

[cv2065]

Check your grounds.

[Jeff Kleiner]

Check your main to dash harness connector. Ron Francis had a run of them in late 2024 into 2025 which were miswired. Notice how the colors don't flow through the plug.

https://thefactoryfiveforum.com/attachment.php?attachmentid=211370&d=1741711762

The affected circuits were flashers and turn signals.

Jeff

[Pete&Scott]

Only one Tan wire runs from the rear harness connector to the dash. That one wire runs to the right taillight with a split to the license plate light and a split to the left turn signal. I found the license plate split. Power is at that location and at the beginning of the harness. Still looking for the end of the left taillight wire. Going to pull the rear harness out to try and figure out where the left split is, or if the wire is just broken. I messaged Dan at FFR about the turn signals, and he said they won't work unless the ignition is on. Hazards work even with the ignition off. I turned the ignition on, and the right and left turn signals work, but don't work if the taillights are on. So, no turn signals at night, which doesn't seem right.



Check your main to dash harness connector. Ron Francis had a run of them in late 2024 into 2025 which were miswired. Notice how the colors don't flow through the plug.

https://thefactoryfiveforum.com/attachment.php?attachmentid=211370&d=1741711762

The affected circuits were flashers and turn signals.

Jeff

[edwardb]

Dan is right about the turn signals being on an ignition circuit. Hazards on a battery circuit. Same as the headlights and running lights. Just fishing here -- did you do the mods to the RF harness described in the build manual? On page 283 in the latest version. Involves cutting a few wires that can interfere when using the hot rod harness connection. Which the Mk5 does with the new turn signal assembly. You should have turn signals with the running lights on. They're separate circuits in the bulbs.

FWIW, to help with troubleshooting (maybe) the 3-wire square bulbs have a dedicated wire for the low intensity running lights which have their own RF circuit. So in theory shouldn't interact with anything. The high intensity lights are either turn signals, hazards, or brake lights. Each has a separate RF circuit input. The ACDelco style turn signal handles the switching through the second wire. The third wire is ground.

[Pete&Scott]

I did cut and tape the pink, yellow, and white wires. I asked Dan about all the other wires, and he said they weren't needed, so tape them all up and zip tie them out of the way/ I just untaped and cut the zip ties to confirm.

Turn signals work when the running lights are not on. Running lights work on both lights after I found a break in the tan left turn signal wire. Will reach out to Dan again today to see if he has any other suggestions.
225453



Dan is right about the turn signals being on an ignition circuit. Hazards on a battery circuit. Same as the headlights and running lights. Just fishing here -- did you do the mods to the RF harness described in the build manual? On page 283 in the latest version. Involves cutting a few wires that can interfere when using the hot rod harness connection. Which the Mk5 does with the new turn signal assembly. You should have turn signals with the running lights on. They're separate circuits in the bulbs.

FWIW, to help with troubleshooting (maybe) the 3-wire square bulbs have a dedicated wire for the low intensity running lights which have their own RF circuit. So in theory shouldn't interact with anything. The high intensity lights are either turn signals, hazards, or brake lights. Each has a separate RF circuit input. The ACDelco style turn signal handles the switching through the second wire. The third wire is ground.

[Pete&Scott]

After pulling the whole harness, I finally got the left taillight working. Seems the left turn signal wire had a break just near the end of the run. Trimmed the cable, and it now gets power. FYI. The wiring diagram in the booklet shows a splice in the wire branching left and right. In reality, two tan wires run all the way to the dash connector and are spliced together at the connector. That confusion led me to try to find the split to see if the left line wasn't properly spliced.

Still have an issue with the blinkers not operating when the taillights are on. I assume something is not working correctly. Any suggestions on how to sort that out? Do I have a bad turn signal switch? Is the turn signal switch supposed to cut power to the taillight switch when the turn signal is engaged? When I hook up the taillight directly to 12v power, I see the taillight is bright, but when I just hookup the the turn signal wire to 12v power, the light is dimmer, so it appears the switch should be dropping taillight power when the turn signal is engaged.

Looking at the Holley Sniper 2 wiring setup to connect to the RF harness. The Holley Manual doesn't have info on how to connect to RF harness. If anyone has connected these two, I would appreciate any wiring instructions or diagrams for connecting the Holley Sniper 2 to the RF harness. It is my understanding that the Holley 2 also controls the fuel pump and the fan and wants direct power from the battery but also has some ignition controls and needs to connect/run through the inertia switch. Lots of wires not in plastic conduit on the main RF Harness, and a pigtail with similar wires but not the same coming off the Holley 2. I have done a lot of 120v wiring but not much 12v so struggling with figuring out where all these wires are going. I am also used to putting things together where all the wires, nuts, bolts all get used. The wiring harness and my Box #1 seem to have a lot of extra items!!!

[edwardb]

After pulling the whole harness, I finally got the left taillight working. Seems the left turn signal wire had a break just near the end of the run. Trimmed the cable, and it now gets power. FYI. The wiring diagram in the booklet shows a splice in the wire branching left and right. In reality, two tan wires run all the way to the dash connector and are spliced together at the connector. That confusion led me to try to find the split to see if the left line wasn't properly spliced.

Still have an issue with the blinkers not operating when the taillights are on. I assume something is not working correctly. Any suggestions on how to sort that out? Do I have a bad turn signal switch? Is the turn signal switch supposed to cut power to the taillight switch when the turn signal is engaged? When I hook up the taillight directly to 12v power, I see the taillight is bright, but when I just hookup the the turn signal wire to 12v power, the light is dimmer, so it appears the switch should be dropping taillight power when the turn signal is engaged.

Needless to say, it's difficult to trace electrical issues on-line. But let me try one more time. First, I'm going to assume the following:
- You made the wiring changes described in the manual. Clipping the purple, etc. You said you did. Not doing so can cause issues as the manual mentions.
- You've checked the rear harness connectors as Jeff K. described and all the wire colors match through the connectors.
- You have the two solid state flashers installed in the RF fuse panel and the ground leads properly grounded.
- You have the kit supplied headlight switch installed, plugged in, and also grounded.
- You have the kit supplied turn signal switch installed and the RF hot rod connector firmly plugged in.
- The front lights are working properly. You should have low intensity running lights on both sides with the headlight switch pulled on. Should flash higher intensity on both sides with the ignition off and the hazard button engaged. Should flash the proper turn signal sides with the ignition on. Running lights should not be affected with either hazards or turn signals. Either on or off. If you haven't tested the front yet, it would be a good place to start. If all works OK it suggests the headlight switch and turn signal switch are working properly. Since these are also used by the rear lights, reduces what to look for there. If the front lights aren't working right, I'd sort that out first.

I've done a number of builds with the RF harness and had some issues along the way, but not ever a broken wire somewhere in a wiring run. Obviously it can happen. But that's the last thing I would suspect. Let me be very clear about another point, a duplicate of one I made before. The turn signal switch is just a series of switches applying voltage to the appropriate wire(s) and changing based on the position of the turn signal stalk, hazard switch, and brake light switch. It does not drop voltage or do anything exotic. Personally, assuming everything I've described so far is exactly right, I'm left with suspecting your rear lights are either defective or improperly wired. Let's confirm each.

Test both rear lights. Note these fixtures, assuming they're the same as the ones I received about 6 months ago, have white ground wires. Many LED fixtures are wired that way and it trips up a lot of folks. The build manual shows this properly, but it's easy to miss. So test them as follows with a power supply or your 12V battery: Ground wire on white, +12V on black should yield low intensity brightness. Ground wire on white, +12V on red should yield high intensity brightness.

Assuming both work properly, this is exactly how the rear lights are wired.

LH:
RF black -> Fixture white
RF tan -> Fixture black
RF yellow -> Fixture red

RH: (almost the same)
RF black -> Fixture white
RF tan -> Fixture black
RF white -> Fixture red

The above is in the build manual so is redundant I guess. But the trailer converter is also referenced and maybe a little confusing. Went ahead and listed it out as part of a troubleshooting process. Note the purple brake wires in the rear RF harness are not used.

Not to confuse the issue, but this is what's happening. The headlight switch puts +12V on the two fixture black wires when the headlight switch is pulled. It's a separate circuit and no reason to interact at any time with the other other wires. The ACDelco switch puts +12V on both fixture red wires when the brake pedal is applied. The ACDelco switch puts +12V on both fixture red wires when the hazards are switched on and they flash via the hazard flasher in the RF panel. The ACDelco switch puts +12V on appropriate LH or RH side red wires based on the turn signal and they flash via the turn signal flasher in the RF panel.

Hope this helps and somewhere in there is the solution to your problem. For the record, my Mk5 build isn't done yet but I have it wired as described and it works properly. So not theory. Good luck. :o

[Jeff Kleiner]

A thought---

Are you sure that your running lights; i.e. tail and parking lights, are not illuminating the high intensity elements rather than the low intensity elements when you turn the lights on? If this was the case the low element would show flashing when the lights are off but when the lights are on the brighter element would override it by being constantly illuminated.

I've seen other builders have this occur when they have reversed the wiring for the high and low.

Jeff

[Pete&Scott]

Thanks for your very detailed explanation. I appreciate your time to put that together. FFR needs to hire you for tech support!!! I did finally sort out the turn signal issues this evening. With all of the left tail light issues that started all of this, in my frustration of trying to fix that issue, I did a lot of testing, which meant pulling out the rear harness and connecting and reconnecting the front and rear lights. In that process, I did notice the brighter and dimmer settings of the turn and tail light circuits, which led me to double-check my turn and tail light configuration. I did get them mixed up on the reconnect. I also found a blown turn signal fuse, not sure if that was an initial part of all of this or a result of the mix-up. Thanks again for your help. Hopefully, your detailed explanation of how the turn signal switch works will help others.


Needless to say, it's difficult to trace electrical issues on-line. But let me try one more time. First, I'm going to assume the following:
- You made the wiring changes described in the manual. Clipping the purple, etc. You said you did. Not doing so can cause issues as the manual mentions.
- You've checked the rear harness connectors as Jeff K. described and all the wire colors match through the connectors.
- You have the two solid state flashers installed in the RF fuse panel and the ground leads properly grounded.
- You have the kit supplied headlight switch installed, plugged in, and also grounded.
- You have the kit supplied turn signal switch installed and the RF hot rod connector firmly plugged in.
- The front lights are working properly. You should have low intensity running lights on both sides with the headlight switch pulled on. Should flash higher intensity on both sides with the ignition off and the hazard button engaged. Should flash the proper turn signal sides with the ignition on. Running lights should not be affected with either hazards or turn signals. Either on or off. If you haven't tested the front yet, it would be a good place to start. If all works OK it suggests the headlight switch and turn signal switch are working properly. Since these are also used by the rear lights, reduces what to look for there. If the front lights aren't working right, I'd sort that out first.

I've done a number of builds with the RF harness and had some issues along the way, but not ever a broken wire somewhere in a wiring run. Obviously it can happen. But that's the last thing I would suspect. Let me be very clear about another point, a duplicate of one I made before. The turn signal switch is just a series of switches applying voltage to the appropriate wire(s) and changing based on the position of the turn signal stalk, hazard switch, and brake light switch. It does not drop voltage or do anything exotic. Personally, assuming everything I've described so far is exactly right, I'm left with suspecting your rear lights are either defective or improperly wired. Let's confirm each.

Test both rear lights. Note these fixtures, assuming they're the same as the ones I received about 6 months ago, have white ground wires. Many LED fixtures are wired that way and it trips up a lot of folks. The build manual shows this properly, but it's easy to miss. So test them as follows with a power supply or your 12V battery: Ground wire on white, +12V on black should yield low intensity brightness. Ground wire on white, +12V on red should yield high intensity brightness.

Assuming both work properly, this is exactly how the rear lights are wired.

LH:
RF black -> Fixture white
RF tan -> Fixture black
RF yellow -> Fixture red

RH: (almost the same)
RF black -> Fixture white
RF tan -> Fixture black
RF white -> Fixture red

The above is in the build manual so is redundant I guess. But the trailer converter is also referenced and maybe a little confusing. Went ahead and listed it out as part of a troubleshooting process. Note the purple brake wires in the rear RF harness are not used.

Not to confuse the issue, but this is what's happening. The headlight switch puts +12V on the two fixture black wires when the headlight switch is pulled. It's a separate circuit and no reason to interact at any time with the other other wires. The ACDelco switch puts +12V on both fixture red wires when the brake pedal is applied. The ACDelco switch puts +12V on both fixture red wires when the hazards are switched on and they flash via the hazard flasher in the RF panel. The ACDelco switch puts +12V on appropriate LH or RH side red wires based on the turn signal and they flash via the turn signal flasher in the RF panel.

Hope this helps and somewhere in there is the solution to your problem. For the record, my Mk5 build isn't done yet but I have it wired as described and it works properly. So not theory. Good luck. :o

[edwardb]

Thanks for your very detailed explanation. I appreciate your time to put that together. FFR needs to hire you for tech support!!! I did finally sort out the turn signal issues this evening. With all of the left tail light issues that started all of this, in my frustration of trying to fix that issue, I did a lot of testing, which meant pulling out the rear harness and connecting and reconnecting the front and rear lights. In that process, I did notice the brighter and dimmer settings of the turn and tail light circuits, which led me to double-check my turn and tail light configuration. I did get them mixed up on the reconnect. I also found a blown turn signal fuse, not sure if that was an initial part of all of this or a result of the mix-up. Thanks again for your help. Hopefully, your detailed explanation of how the turn signal switch works will help others.

You're welcome, for whatever little I provided. Sounds like you have it sorted. It doesn't take much for things to go south and leave one questioning often more than what is the real problem.

[Jeff Kleiner]

So, it was the result of having the high and low intensity leads reversed! As I mentioned I have seen others get bitten by doing the same. Happy to hear that you sorted it out.

Jeff