Turn signals pulsing at low RPM

[krafty]

OK, so I just got a new LED flasher relay in the bike to get the LED turn signals flashing, but at low RPM not only do they flash, they pulse rapidly. I have a feeling it has something to do with the reg/rec (Sparck Moto) but I'm not entirely sure. I don't *think* I'm seeing any pulsing in the headlight at idle, but with the twin vibrations it's a little hard to tell.

I haven't had a chance to do a whole lot of diagnostic - I know I'm charging. At idle I show pretty much battery voltage (gotta love stock CB350 charging systems) but when I rev the engine it bumps up to around 13.9-14v. Not that it would cause this issue, but the turn signals do have a diode wired in for the indicator light.

I'm pretty sure I have the reg/rec wired in correctly, it had the factory plug plus the black wire which I wired into a black wire if I remember correctly.

Any ideas where I should start looking, or should I just expect to give any nearby epileptics seizures when I'm stopped with a turn signal on?

 

[Sonreir]

Make sure your spark plug caps are the resistor type or that you're using resistor plugs. It's common to get a bit of flashing on LED lights because the spark plugs (when they fire) create a bit of a magnetic field. This magnetic field is picked up by nearby wires in the same way your antenna picks up radio signals from the air.

The difference here is that LED lights require very little current and they immediately luminesce, unlike their incandescent counterparts. If possible (it usually isn't) avoid routing your wiring harness by the coils or plug wires.

 

[krafty]

Hmm... I have the NGK resistor plug caps (I think) but I don't think I have resistor plugs. I'll double-check.

 

[Sonreir]

One or the other is fine. Both are not necessary.

 

[mannydantyla]

You'll know if they're resister plugs if there's a "R" in the part number printed on the plug (at least that's true for NGK)

You'll know if they're resister caps if you're ohm-meter reads around 5k ohms, IIRC.

 

[krafty]

The caps are definitely resistor caps, 5k ohms. I guess I'll have to play with a bit of wire relocation, although there isn't much I can do.

 

[mydlyfkryzis]

How low is low RPM? at low RPM, the alternator doesn't put out a steady voltage, there is some pulsing. I can see it when I get below 900 RPM. A CB350 should be idling about 1200 RPM. Any lower, and some pulsing will be seen, especially with LEDs.

do you have a stock battery, or a smaller one, or just a capacitor? A small battery will drain pretty quickly at idle and not buffer the voltage out of the alternator. Same with a capacitor.

Also, do you have the white and yellow wires off the alternator connected? If you rewired the bike and did not do that, you may be running off of one or 2 pairs of coils, which would also cause the pulsing you talk about.

 

[krafty]

It still does it at ~2k RPM. Slightly smaller battery ( http://www.batterystuff.com/powersports-batteries/sYTX7E.html ) but even with the battery fully charged and immediately after starting it still does the same thing.

Everything is connected, factory harness w/ the Sparck Moto regulator/rectifier being the only upgrade.

I may just end up living with it, we'll see. I switched to LED turn/tail/stop lights primarily because of the slightly smaller battery I had to fit (in order to clear the seat) to help reduce the overall draw. The only other things not factory are the DCC universal coils and the LED-specific flasher unit. I wonder if I should switch to one of the 2 prong flashers that have the separate ground wire - something like this: https://www.bobdrake.com/ItemForm.aspx?Item=HR-90650

 

[Sonreir]

I run a full LED setup on my bike (including gauges and headlight) and I've not had a problem with the standard two prong setups. I don't think just throwing money at it will solve the issue. :-\

 

[Garage_guy_chris]

I have a CB 450 with similar mods battery reduced from 12ah to 7ah podtronics combined reg/rect. that is doing the same thing you get a flashing/pulsation in the LED lights both the turn signals and the tail light / brake llight. I have tried disconecting the charging system with the same flashing/pulsations. a friend noticed the flashing changes with the engine RPM's so im pretty sure its related to to the ignition system.

I dont think its radio noise, i think it is the coils injecting noise back into the harness or the power pulses going to the coils. I would like to find a solution to this problem but not very knowledgeable when it comes to electronics

 

[sancho]

I've got the same thing going on after installing led tail bulb, it pulsates in sync with rpm. I will try the resistor plugs, i think my plug caps are 0ohm.