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Turn signals flash when on battery, solid when motor running?


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Hey guys,

 

Bit of a weird one with my 1922 Cadillac that has us stumped.

 

I have LED turn signals (from Snyder’s) and a 6v positive ground electronic flasher, which work perfectly when the car is on battery.  


As soon as the engine is running they stay solid (with occasional flickering) but do not flash. Turn the motor off and they go back to flashing properly

 

Im thinking that the power is dirty or fluctuatating too much but not really sure how to test it or fix it.

 

I tried adding a load resistor that you would

normally use with a thermal flashing can and had the same result 
 

Any ideas would be welcome?

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I'd start by checking the voltage at the flasher connector (1) engine off and (2) engine running.  Look using both DC and AC scales on the meter (there should be no AC voltage).  It sounds as though something (noise, or poor connection?) is reducing the voltage that the flasher sees.  I would expect the flasher to have a solid state regulator built-in so that voltage greater than 6 would not be an issue (i.e., normal charging voltage).

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I wonder if another electrical item is stealing the ground. My experience is if something works electrically by itself and then goes into any sort of improper operation with other electrical items operating. One of the other items is stealing the affected items ground.

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When you turn the key or switch to “on” to get the engine to run are you energizing a point that is normally at zero volts when the engine is off that is feeding back to the turn signal wiring?  Grounding is always suspect in conditions like this.

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13 hours ago, certjeff1 said:

I wonder if another electrical item is stealing the ground. My experience is if something works electrically by itself and then goes into any sort of improper operation with other electrical items operating. One of the other items is stealing the affected items ground.

 

I've got the can grounded to the body via a bolt through the fire wall, or is it possible that the lights are the issue? 

20 hours ago, EmTee said:

I'd start by checking the voltage at the flasher connector (1) engine off and (2) engine running.  Look using both DC and AC scales on the meter (there should be no AC voltage).  It sounds as though something (noise, or poor connection?) is reducing the voltage that the flasher sees.  I would expect the flasher to have a solid state regulator built-in so that voltage greater than 6 would not be an issue (i.e., normal charging voltage).

We did a couple of measurements yesterday and saw the occasionally reading on AC - the flasher can its self seems to have a good connection with a good ground so I'm wondering if it's just the quality of the power isn't good enough for the electric flasher. Is there any easy way to smooth out or filter the input power? 

 

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When I talk about grounds do you have any small body grounds in the system. Most likely from the factory you only have a main battery ground. You might need to add small 12ga body grounds to the system. Adding them where? That depends on where you have mounted the light assemblies. You might even need to add one to the firewall. Since that is where you mounted the flasher. The more electronic devices you add the more small grounds you need. What kit did you buy from Snyders?

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Is your generator case grounded? I have a set of LED lights that run on my Model A Ford and kept having flashing issues. I even blew out the LED's on one lamp. I sent them back to United Pacific and they informed that they appeared to have been blown by a power surge. Since the only ground for the generator case is via the mounting hardware (bolts & sliding brackets) I grounded the case to the engine using a #10 stranded wire. Never had an issue again.

 

Frank

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I understand that old car generators produce "noisy" power that cause LED issues.  That is probably why they work OK on the battery and not while running.  

 

Causes and corrective actions

The main cause of noise can usually be found in the LED driver of the lamp. With LED lamps, driver electronics are integrated; for example with LED ceiling lights, the driver is usually located in the base. This electronics consists of several components. These include:

  • Switching power supply
  • Coils/chokes
  • LED driver

The switching power supply generates the operating voltage for the LED’s from the 120V mains voltage. This part of the electronics contains, among other things, a small transformer for transforming the voltage. Furthermore there are some coils or chokes for the intermediate storage of energy as well as for the avoidance of EMC disturbances. The LED driver usually contains capacitors for smoothing the voltage.  https://lamphq.com/noisy-led-lights/

 

 

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Hunter,

Let's try another dumb idea.

Swap out one side of the car back to standard bulbs.

Say the driver's side, front and rear turn signals.

Retry the battery direct idea, with the ign switch in the off - on - running positions.

Then the question will be, do both turn signals L / R work in these 3 positions?

 

This test will really screw up your thinking..........

Good luck mate.........

 

Mike in Colorado

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  • 2 weeks later...

Sorry for butting in here, but did you ever check the voltage at the input to the flasher when the key was on? You could have a weak battery, or bad connection that when you are powering everything pulls the battery voltage down. Another thing is that there should not be any kind of "driver" for this application. The LED only requires 20 or so milliamps of DC to run. The LED lights probably have a resistor in them to limit current for the rated input voltage. You said I believe that they are 6V LED's right?

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I had issues running LED park/turns signal globes in my  ‘38 Buick. Seemed the overseas manufacturer had wired the dual filaments together. The flasher would work properly on one side and the park would flash on the opposite side. After spending countless hours and hours of testing and retesting effort, gave up and installed regular 6volt globes. All works as it should.
 

LEDs sound like a good idea for vintage cars and in many cases, work fine, but not on mine.

 

just my two bobs worth 😀😀😀😀😀😀😀

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So the pilot light staying on is because the can is stuffed (i've had two do the same thing) and found a number of people reporting the same failures. 

 

I might try a 12v can and see if it will work - i opened up one of my dead cans and it was actually rated to 240v

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  • 2 months later...

Alright finally got another chance to play with it and I'm still no closer to understanding what's going on 

 

Turn signals flash perfectly when the car is turned off and stay on while the car is running, things I tried today with the same result

 

Added a rectifier (no change) 

Bypassed the signal-stat and connected an indicator to the flasher can using a regular switch (no change) 

Brake lights in the same housing work fine when the car is running (no flickering and only come on when pedal is depressed)

 

The battery is fully charged and the voltage sits around 7.1 amp at idle and doesn't seem to jump around. 

 

I'm really at a loss what to try next 

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To hidden hunter. I can’t offer any particular kind of answer. I think the people above are right about earthing. My anecdote was with the actual turn switch. Unbeknownst to me there was a tiny idiot light inside of it which would feed back and all the turn lights would flash; which ever way you turned the lever. I removed the light and all was well which educated me on how little power LED lights consume.... Obviously there is something all of us have overlooked, globally, believe it or not!!! ... In the meantime , my only suggestion is to get a small rechargeable battery pack to operate them independently from the main power supply. It could be removed to recharge or connected to the car. If connected and the problem persists, try and connect it so it is only connected when the ignition is turned off. I.E. when the car is parked. You will need a particular type of ignition switch to do this or a relay, or a diode and someone more clever than I on this forum to tell you how to wire it in. Sorry I can’t help more. 

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  • 2 weeks later...

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