Topic: Right Turn Signal Won't Flash with lights or fog lamps on

[rocket289k]

Hi Everyone,

I have a strange issue that recently cropped up on my Metuchen July 65 built GT. My signal lights work properly except when the lights or fog lamps on. The car is completely restored including the wiring. This problem just suddenly manifested itself after months of working properly.

The Issue

When the park lights, headlights or fog lights are on the left hand turn signal works fine but the right hand turn signal won't flash. The indicator light will come on and the front and rear signal light illuminates but it won't flash. The left hand turn signal is not affected and works properly. I'm at a loss. I've never had this problem before. Any thoughts folks?

Regards,

Ron

[midlife]

Probably the turn signal switch is going bad.  These are notorious for their unreliability.

[67gtasanjose]

Check for continuity in the "ground" wire within the RIGHT front light. This stinks high of a bad ground wire, backfeeding through the park light circuit. The flasher unit (with a bad ground) isn't drawing enough current to operate the rear light, that is why IT is coming on but not flashing. Usually in the bulb socket, but I'm not looking at a wiring diagram for your model, just following experience from countless other cars I've worked on with the same symptoms.
Not to undermine the possibility of a bad switch (it still could be) just that since you described that it seems to work fine with the park lights OFF, that steers me away from that answer.

Richard

[midlife]

Check for continuity in the "ground" wire within the RIGHT front light. This stinks high of a bad ground wire, backfeeding through the park light circuit. The flasher unit (with a bad ground) isn't drawing enough current to operate the rear light, that is why IT is coming on but not flashing. Usually in the bulb socket, but I'm not looking at a wiring diagram for your model, just following experience from countless other cars I've worked on with the same symptoms.
Not to undermine the possibility of a bad switch (it still could be) just that since you described that it seems to work fine with the park lights OFF, that steers me away from that answer.

Richard

But the right turn signal light uses the same grounding point as the parking light.  With foglamps or headlights on, the parking lamp is off, so the turn signal should also work just fine.  I'd also look at the bulb socket itself: reproduction units are not that good in quality and sometimes contact points just aren't up to snuff.

[CharlesTurner]

As Randy mentioned, repro parking light sockets are terrible and can cause issues like this.  I suppose you've checked to make sure the bulb is ok?

[rocket289k]

Thanks for the replies everyone.  I really appreciate it.  I have some new information to add to this issue so I'll break it down into its component parts.

Issue Details:

#1 (new) - When starting the car in the garage I placed my foot on the brake.  I hadn't noticed this before but the dash lights come on every time that I step on the brake pedal.  This issue started at the same time the signaling issue appeared.

#2 (new) - Headlights off, fog lights off, when signaling to the left all is well (no issues) - both the front turn signal light and rear tail light flash as does the interior left signal light.  When signaling to the right the front turn signal light and rear tail light flash as does the right interior signal light however the dash lights flash on and off with each cycle of the right turn signal.

#3 (originally posted issue) - With either the park lights, the headlights or the fog lights on the left turn signal works properly however the when engaging the right turn signal the front turn signal light and rear tail light illuminate as does the interior right signal light but they do not flash


Now I'll respond to the comments / questions that people had in order:

Midlife (Randy) - re: turn signal switch is going bad.  I suppose that is possible.  However, during the restoration I installed a brand new original Ford turn signal switch.  So I'd hope the switch itself would be ok but you never know it was one of the items on my list to check out.

Randy and Charles - re: repro parking light sockets.  I haven't had a chance to swap out the bulbs just to make sure it isn't an issue with bulb and how it's seated in the socket.  The comment on the repro parking light assembly does apply in my situation as well as I did use repro parking light units.


Regards,

Ron

[67gtasanjose]

Issue Details:

#1 (new) - When starting the car in the garage I placed my foot on the brake.  I hadn't noticed this before but the dash lights come on every time that I step on the brake pedal.  This issue started at the same time the signaling issue appeared.


pull the rear bulb, see what the effect is

#2 (new) - Headlights off, fog lights off, when signaling to the left all is well (no issues) - both the front turn signal light and rear tail light flash as does the interior left signal light.  When signaling to the right the front turn signal light and rear tail light flash as does the right interior signal light however the dash lights flash on and off with each cycle of the right turn signal.

same as above

#3 (originally posted issue) - With either the park lights, the headlights or the fog lights on the left turn signal works properly however the when engaging the right turn signal the front turn signal light and rear tail light illuminate as does the interior right signal light but they do not flash

I get the feeling when you fix the cause of the above, the flasher will work


Now I'll respond to the comments / questions that people had in order:


It would seem my earlier comments on bad grounds wasn't considered. A poorly designed cheap aftermarket socket or bulb can also be the sourse of a bad ground, this is why the continuity test was suggested. Any dual element bulb used on nearly every car on the road has two filements inside of them, each connected to two different circuit, e.g. turn light and taillight. The bulb shares the same ground to illuminate the bulb. If no ground is available for any reason the circuits will become merged (feedback) through the two filaments of the bulb. This "merged circuit" will not prevent the bulb from illuminating, however it is using the "other" circuit to provide a ground path through all the other bulbs of the other circuit that is powered down (off). Removing the bulb(s) will remove the "merge(s)" in the circuit(s). I live in the rust belt (Ohio) I am a proffessional mechanic and electrical issues like this are one of my specialties. Although "rust" or a bad connection where the ground wire(s) are connected to the body might NOT be your issue, it is seems definite a bad ground is causing the problem. (likely in one of these sockets) The newly mentioned problem of the brake lamps causing the dash lights to come on also now leads me towards the back of the car.  Actually, it could be two problems, so if only pulling the bulb out of the right rear brake lights doesn't stop the dash lights from flashing, try also pulling out the front right bulb. Now the dash lights should not be coming on with the turn signal or brake lights...start there and work out.

Richard
[/quote]

[67gtasanjose]

But the right turn signal light uses the same grounding point as the parking light.  With foglamps or headlights on, the parking lamp is off, so the turn signal should also work just fine.  I'd also look at the bulb socket itself: reproduction units are not that good in quality and sometimes contact points just aren't up to snuff.

+1 and 100 percent agreed. All due respect Randy, but as noted in my quote, a continuity test can prove or disprove an assumed good ground.

His "new" problems seems to now point at the rear of the car. Are not the 66 and older Mustang tailight/stop lights grounded through the mounting of the lamp or do they have a seperate grounding wire like the 67-up do? (haven't worked on one of those in years) If the body of the tail/stop light isn't grounded good to the painted panel of the back of the car, this would be a possible source of a bad ground. A poorly produced part could also be the cause.

Richard

[midlife]

The problem labeled #1 sounds awfully familiar, related to the whole problem of the four-way flasher design of that period.  If the e-flasher is on, then applying the brake applies constant power to all four corners.  This is the reason why Ford changed the design mid-way through 1966, but it still didn't fix the problem. 

I would disconnect the four way flasher and see if the other problems still persist.

As for grounds, yes, that is still a concern.  On the rear tail-light socket, there are tabs for the two filaments on the bottom of the socket.  I have seen numerous occasions that these tabs touch one another --- another area that deserves inspection.

The way to attack all of these problems is to simply the electrical circuitry as much as possible.  Remove 4-way flasher from the equation.  Then if the problem persists, remove front or rear bulb and try again.  Isolate the problem to a single circuit.

[67gtasanjose]

The problem labeled #1 sounds awfully familiar, related to the whole problem of the four-way flasher design of that period.  If the e-flasher is on, then applying the brake applies constant power to all four corners.  This is the reason why Ford changed the design mid-way through 1966, but it still didn't fix the problem. 

I would disconnect the four way flasher and see if the other problems still persist.

As for grounds, yes, that is still a concern.  On the rear tail-light socket, there are tabs for the two filaments on the bottom of the socket.  I have seen numerous occasions that these tabs touch one another --- another area that deserves inspection.

The way to attack all of these problems is to simply the electrical circuitry as much as possible.  Remove 4-way flasher from the equation.  Then if the problem persists, remove front or rear bulb and try again.  Isolate the problem to a single circuit.

+1 ISOLATE the problem

[rocket289k]

Hi Guys,

Since it's a '65 Mustang we can eliminate the four way flasher from the equation.  My car doesn't have a four way flasher installed.

Regards,

Ron

[rocket289k]

Hi Everyone,

I finally had an opportunity to begin to diagnose the issue.  A number of you were correct in that the issue definitely originated at the rear of the car.  Once I disconnected the right rear tail light wiring pigtail everything worked properly (so I was able to isolate the problem area quickly).  Long story, short it turned out that the wiring pigtail was not pressed onto the right tail light properly.  Once I made sure I had a good connection the issue was resolved.  Thanks again to everyone who helped me diagnose the problem.  I really appreciate everyone's input as always.

Regards,

Ron

[midlife]

Good job! 

[67gtasanjose]

 Long story, short

any punn intended? +1, good job

[jwc66k]

Long story, short it turned out that the wiring pigtail was not pressed onto the right tail light properly. 

Ron,
Good job. It's the simple solutions that are the most difficult. But, technically it's an "open".
Jim