Turn Signal Conundrum

[jayb]

I'm having a turn signal issue on my 69 Cobra.  I had originally installed new bulbs in the taillights and front turn signal/marker lights, and when I finally got the battery installed last week I checked the operation, and found that the emergency flashers worked fine, but the turn signals did not come on, in either direction.  I swapped the flasher units, and had the same issue; all emergency flasher lights worked, but nothing on the turn signals.  After checking for power and confirming that the turn signal circuit had power (it is on a separate fuse from the emergency flasher circuit), I decided to upgrade the whole mess.

I bought a new turn signal switch (which is where I figured the problem was), new flashers that were LED compatible and also compatible with a combination of LED and incandescent lights, and new LED lights for the taillights, turn signal/marker lights, and the turn signal indicators in the hood.  The only remaining incandescent bulbs are the indicator lights in the dash.  Got it all back together a few days ago, and now the emergency flashers still work fine, and now the turn signal lights turn on, but they still don't flash.  Again I swapped the flashers and got the same thing, again checked the power going to the turn signal switch and confirmed it was good, but still no turn signal operation.

Now normally if you have lights that turn on but don't flash, you have a bulb out.  But all of the bulbs work, with the emergency flashers operating and with the turn signal switch in both positions.  I'm thinking a ground could be a problem, but the lights have always been bright, even with the original incandescent bulbs, and since the emergency flashers work perfectly, it doesn't seem to me that a bad ground is the issue.

I've gone to the trouble of getting a complete wiring diagram for the car, and have traced all the wires, and everything looks to be where it is supposed to be.  Any ideas on this?  Thanks for any comments - Jay

[gregb]

I think I'd suspect the flasher units, what brand?  When you have the hazards on, all the bulbs probably give it the required load, maybe one side just isn't enough? 

[jayb]

They are Ron Francis Wiring flashers, designed to work with zero load for use with LED bulbs.  I've stuck the incandescent bulbs back in, and no difference.

[gregb]

Try bypassing the flasher with the signal lever one way or the other.....see if the bulbs light

edit, nevermind, I  see you said  that the bulbs come on.....

[AmerigoHauler]

I'm just throwing this out there.

My 1974 ford pickup lighting circuit has all original wiring, sockets and T/S switch. Everything worked good with incandescent bulbs and I bought everything I needed to convert from an outfit that sells LED kits and stuff.

Everything would light and flash OK until you replaced the last incandescent with an LED. Didn't matter what socket, 3 LED's and 1 incandescent OK, 4 LED's no flash.

Tried different flashers, same problem.

I'm not an electrical wizard but I spent most of my career as electric forklift mechanic so I am at least familiar with DC circuits. I have full prints and I just could not see why it was doing this and all tests showed no issues with my wiring system.

After research I bought a set of LED bulbs that where non polarized. Put them in and everything worked great.

That was in 2018 and I've had no issues since.

Erich

These are the bulbs I used to make my system work with no modifications.

https://www.amazon.com/gp/product/B077T1DC9B/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1

[jayb]

I just refitted the whole car with a factory style flasher and all incandescent bulbs.  Still behaves exactly the same.  Baffling...

[mbrunson427]

Jay, are you sure that you have a good clean ground?? Could it be that simple? I'd check my ground locations.

[jayb]

I have checked those already, that was one of my first thoughts.  Maybe I have a bad wire in the harness or something, because all the grounds appear to be good.  The lights are super bright though, which also seems to indicate the grounds are OK.  Go figure.

By the way Mike, you shipped a couple of your air filters to my friend Gary Kollofski in California, and he really likes them - Jay

[cleandan]

Good day Jay.
Try verifying the parts you are working with work on their own independent of the Cobra you are working on.
Put the flasher in a different car to see if it functions.

Of course the lights function already.

Use a meter to verify the signal switch is functioning independed ot the wiring.

Once you have proven the flasher, bulbs, and lights work it is left to the wiring....and this is where the fun begins.

Tedious work but you must go wire by wire, section by section, proving all is working properly.
If you have a load tester even better because sometimes these old wires corrode inside the insulation and basically become resistance wires rather than current transfer wires.

If there are any connectors be sure to test both sides of those to prove they are correct too.

Don't forget to verify the main light switch, and brake light switch too.
All the marker lights and signal lights go through the headlight switch and this can cause some odd issues because of its interaction....same with the brake light switch.

This is where jumpers become helpful in isolating the switch as the culprit.

[Chuck]

Let's assume the old switch had dirty or bad contacts and that's why they stopped working. With the new switch they light up but don't flash. The emergency flashers work proving out the bulb circuits, so no need to go there. The emergency flasher needs power to work with the car off. The turn signals only work with the car on so that flasher gets key on power. Flashers are automatic resetting circuit breakers. That's why they flash faster when you have a bulb out. Less heat is generated causing it to reset faster. LED's don't draw the power of incandescents and need a different flasher or load added. Power for the turn signals comes from the key on fuse to the flasher and into the switch. Activating the switch connects the power from the flasher through contacts to the front signals and dash indicators along with another set of contacts for the rear signals. The brake light switch energizes the same filaments so that is part of it too, the signal when activated needs to blink when the brake is on.
 The first thing I would do is put the switch in a turn position. Car off no lights car on turn signal requested on steady, remove the turn signal flasher. The light should go out with no flasher. If the lights go out test the flasher, apply power to its power terminal and connect both filaments of an 1157 to the other. When you ground the bulb the flasher should open and close causing it to flash. If you remove the flasher and the turn signals stay on when requested, then the load isn't going through it and power is coming from somewhere else. Check your brake light switch input to the signal switch, it should only be on when you hit the brakes. I believe the horn contact provides a ground to activate the horn but I'd have to look that up. Pull fuses one at a time until the signals don't light to find the source of power if they light without the flasher. Replace the flasher if it doesn't blink as tested. Do you have proper horn activation & brake lights? With the emergency flashers on, what lights do what with your foot on the brakes?

[jayb]

Thanks to Dan and Chuck for some really good suggestions.  Dan, I looked at the schematic and saw that one of the wires from the headlight switch does go to the turn signal switch, but it appears to be connected externally to another wire, and isn't affected by the headlight switch internals.  I flipped the lights on in different positions and tried the turn signals anyway, but still they were solid on, no blinking.

Chuck's suggestion for looking at one side of the flasher while the other side was plugged into power made sense to me, so I tried that and found a very strange result.  I made up a couple of jumper wires to run from the connector under the dash to the flashers just so I could monitor voltage input.  Both the emergency flasher and the turn signal flasher were getting 12.5V, but the emergency flasher flashed on the output side, and the turn signal flasher did not.  Scratched my head over this for a while, but finally as I was staring under the dash at the two flasher connectors I figured it out.  I had gone through the circuit diagram numerous times and knew which color wires got power; on the emergency flasher circuit it was a red with white stripe wire, and on the turn signal flasher it was a blue wire.  Of course the flashers can only go onto the connector one way, and I saw that the voltage input connection on one connector was on the left terminal, and the voltage input connection on the other flasher was on the right terminal!

I connected my jumper wires to the turn signal switch flasher, and swapped the wires at the connector, and the turn signals flashed!  So, problem solved; but...

But then I got to thinking about the factory style flashers, which were essentially just a switch that opened and closed.  In that case it shouldn't matter which terminal got the power, the switch contact would still heat up and force a flash.  I had gotten a replacement flasher from Napa a couple days ago, and that was the one I was using.  I unplugged it and replaced it with the electronic flasher from Ron Francis Wiring, and checked to see that the turn signals still flashed.  Then I pulled the top off the flasher from Napa; sure enough, it was electronics inside.  So the lesson I'm taking away from this is that the electronic flashers are polarity sensitive, but the factory style flashers probably are not, given the way the Cobra is wired.

In any case, now the turn signals work.  Of course, there is more work to do.  I took the car out for its first test drive on Thursday, and after idling in the driveway at 180 for 15 minutes, it went up to 240 in one lousy mile of driving!  The radiator looks like junk, and it is probably is.  New radiator and electric fans are coming on Monday, so hopefully I'll finally get some miles on this thing next week.  Thanks again for all the suggestions from the forum - Jay

[machoneman]

Electrical gremlins are the worst! Good you figured it out. My recent issues with my 70's brake lights was easy in comparison once I found chafed wires.

[WConley]

This is a really great community!  I bet I could ask a question about a 1948 Crosley and somebody here would chime in!

[Stangman]

Are you going to use a OEM type radiator or are you going to use your Crossflow radiator from summit you told me about a while back.

[jayb]

I'm using a crossflow radiator, but not the one I told you about.  The battery is in the way of going too wide, so this radiator is only 26" wide.  Still has the same 2 core 1" tubes, and I will be putting two 11" Spal pusher fans in front and ditching the fiberglass flex fan that is currently on the car.