Made headlight harnesses now they pulsate - JKowners.com : Jeep Wrangler JK Forum
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post #1 of 29 Old 06-11-2009, 08:45 PM Thread Starter
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Made headlight harnesses now they pulsate

Swapped my Delta bulbs to Hella 55/100s today and I was concerned about the 100w and the canbus getting into an argument so I got off my butt and finally built a wiring harness for the headlights.
Now they pulsate like a car with too much stereo for the electrical system.
But it does it with the jeep running and nothing else on.
Doesn't seem to be any rhyme nor reason, they just fluctuate occasionally.
They do it at idle or while driving, hi or low beam.
Also they seem to dim a little as soon as I come off idle (backwards of what I would expect if it were a power problem)

Harness is simple - 10G from battery to pax headlight area split to 2 40 amp relays (one hi beam, the other low) driven off of the stock headlight plug on that side, then the relay outputs split to the headlights.
All 10G wires and the headlights themselves are grounded to the body within 12" of the bulb.

Maybe need to I run a ground back to the battery?

The light output is FREAKIN ASTOUNDING!
Hi beams look like I have my off road lights on!
Just need to stabilize it somehow.

I just don't know why they would be fluctuating with a 10G run essentially straight to the battery.

Any ideas?


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post #2 of 29 Old 06-11-2009, 09:25 PM
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I would have to say you most likely have a ground issue. When you ran the ground wires to the body did you clean the paint away first?
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post #3 of 29 Old 06-11-2009, 09:51 PM Thread Starter
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yeah a ground issue is about all I could think of
the ground on the passenger side is actually a factory ground point, I took the nut off and slipped the ring terminal over top of the factory braided ground/ring terminal.
Drivers side was a body bolt, they baint the body after its assembled so there's no paint under the bolt.

I'll try cleaning the ground points.
I'll also try running a temporary ground wire from there to the battery

I need to look closer and see if it's both lights or just one


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post #4 of 29 Old 06-11-2009, 11:08 PM
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Are they flickering like the relay is kicking in and out? If so, I would try putting a diode in series with the relay coil, and a capacitor across it(the relay coil). If this is unclear let me know and I can explain better.
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post #5 of 29 Old 06-11-2009, 11:09 PM
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Does it happen with the engine off?
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post #6 of 29 Old 06-11-2009, 11:25 PM Thread Starter
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Quote:
Originally Posted by DED HED View Post
Are they flickering like the relay is kicking in and out? If so, I would try putting a diode in series with the relay coil, and a capacitor across it(the relay coil). If this is unclear let me know and I can explain better.
nope, not like the relay is dropping
just like I said, they are dimming a little like when you have too much amp and not enough alternator/stiffening cap
weird part is that they dim when you bring the rpms up off of idle instead of getting brighter like you would expect with a lack of power problem

They don't seem to be doing it when the engine is off, I need to do more testing and find out for sure
I just did the harnesses and took it for one test drive


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post #7 of 29 Old 06-12-2009, 04:05 AM
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did you meter the lights to see what the voltage is?

'92 YJ
'13 WK2
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post #8 of 29 Old 06-12-2009, 05:03 AM
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Quote:
Originally Posted by DED HED View Post
Are they flickering like the relay is kicking in and out? If so, I would try putting a diode in series with the relay coil, and a capacitor across it(the relay coil). If this is unclear let me know and I can explain better.
My pre-made Susquehanna wiring harness came with the diode/capacitor installed to the relays. It's 12 gauge and I have zero problems with the 130/100 Hella Yellow Star H4 bulbs. They are bright as heck, and I have never noticed them flicker a single time.
I was running the Osram 85/80 bulbs which I was very happy with. Changing to the Yellow Star bulbs gives the light a warmer output, and with the increase in wattage I haven't lost any range on low or high beam.
I also added Osram 55w all weather bulbs to the FabFour bumper mounted 90mm Hella fog lights. They are a good match to the Yellow Star Hella bulbs, but I'm planning on some yellow tint film on them as well.
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post #9 of 29 Old 06-12-2009, 05:43 AM
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put a cap across the trigger wire for the relays.

you are not getting flicker because it's filament bulbs

it's the same issue though
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post #10 of 29 Old 06-12-2009, 07:08 AM
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Basically what everyone else has said....

Use an elecrolytic cap, 100uf 35v or higher across the relay coil, observe polarity, plus to plus, ground to ground. Then put a 1N4001 or higher diode in series with the positive lead to the relays. This keeps the computer happy. The signal to the lamps is PWM (pulse width modulated), you can check the frequency if you have a counter. This should solve the problem.

/jl

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post #11 of 29 Old 06-12-2009, 10:28 AM Thread Starter
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Thanks for the replies guys, I'll try this tonight assuming radio shack has what I need.
Kinda explains why I was seeing 9-10V on the low side and 12.x on the hi side while on hi-beam and vice versa at the factory plug


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post #12 of 29 Old 06-12-2009, 11:12 AM
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if I remember correctly from jk-little pecker, you had to put a resistor on your trigger wire (from the headlight plug because the can bus is searching for the correct voltage. can't remember what size cap to use but im pretty sure that is you problem
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post #13 of 29 Old 06-12-2009, 11:17 AM
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I have a relay on both high and low beams triggered by the stock wiring.

I only added a capacitor... no diode and no resistors. Been this way for about a year with no issues, no codes, nothing.
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post #14 of 29 Old 06-12-2009, 12:57 PM
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yeah when I swapped to HID set up the high beams would flicker like crazy, added the cap and has been perfect since. if you can't find the correct cap to use pm me and ill go through all my cibie stuff that I haven't installed there are two or three in the bottom of that tangled mess of wires.
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post #15 of 29 Old 06-12-2009, 03:44 PM
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Quote:
Originally Posted by paragon View Post
I have a relay on both high and low beams triggered by the stock wiring.

I only added a capacitor... no diode and no resistors. Been this way for about a year with no issues, no codes, nothing.
The diode is a gate for the canbus system. Relay coils produce brief high voltage spikes when switched off. The diode keeps the spike from running backwards through the system.

Normally the diode is connected "backwards" across the relay coil to provide protection. Current flowing through a relay coil creates a magnetic field which collapses suddenly when the current is switched off. The sudden collapse of the magnetic field induces a brief high voltage across the relay coil which is very likely to damage transistors and ICs. The protection diode allows the induced voltage to drive a brief current through the coil (and diode) so the magnetic field dies away quickly rather than instantly. This prevents the induced voltage becoming high enough to cause damage to transistors and ICs.

50 cents is cheap insurance.

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post #16 of 29 Old 06-12-2009, 05:17 PM
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daniel sterns website has diagrams and all kinds of info also.
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post #17 of 29 Old 06-12-2009, 05:33 PM Thread Starter
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went to crackshack and bought caps and diodes - whopping $4.06!
I'll install them and try it tonight
thanks for the info guys!


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post #18 of 29 Old 06-12-2009, 05:42 PM
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Watch the polarity of the diodes also, the band goes to the relay side.

/jl

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post #19 of 29 Old 06-12-2009, 05:51 PM
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the pigtail connectors that came with the relays I bought (in bulk pack of 10 or 20 a few years ago) have the diodes across the coil already. I think they were Hellas also.

But I was under the assumption that someone was referring to inlining a diode on the trigger wire
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post #20 of 29 Old 06-12-2009, 05:55 PM
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Quote:
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But I was under the assumption that someone was referring to inlining a diode on the trigger wire
Yes, we were. Well, I was anyway.

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post #21 of 29 Old 06-12-2009, 06:07 PM
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Yes, we were. Well, I was anyway.
but that's not the best method.

it can cause inductive spikes through any wires running nearby also. that's why they say it's best to diode across the coil of the relay

caps apparently also help reduce the effect of "backfeed" through the trigger wire itself
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post #22 of 29 Old 06-12-2009, 06:51 PM
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I think John is saying with the PWM system the JK uses, you want both, the one inline with the trigger signal, and the other across the coil to prevent the inductive kick at shutoff.
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post #23 of 29 Old 06-12-2009, 07:22 PM
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Quote:
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but that's not the best method.

it can cause inductive spikes through any wires running nearby also. that's why they say it's best to diode across the coil of the relay

caps apparently also help reduce the effect of "backfeed" through the trigger wire itself
Correct, not the best method. But, in this particular circuit, the inline diode clamps anything traveling back into the canbus. Remember, the feed for the coil is from the canbus system. I wanted to isolate the coil from the circuit, so the inline diode is the ticket.

The cap is to smooth the PWM signal to the point at which coil sees it as a constant current source and not a square wave.

/jl

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post #24 of 29 Old 06-12-2009, 09:09 PM Thread Starter
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You guys rock!
Added the caps and diodes per John's instructions and it's rock solid!

thanks a bunch!


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post #25 of 29 Old 06-13-2009, 05:16 AM
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Correct, not the best method. But, in this particular circuit, the inline diode clamps anything traveling back into the canbus. Remember, the feed for the coil is from the canbus system. I wanted to isolate the coil from the circuit, so the inline diode is the ticket.
here's how I understood it: You can diode the trigger wire and that will stop spikes/voltage traveling back up the wire. But inductance caused by the collapse of the magnetic field in the relay can cause spikes through nearby wires. So, by not dioding across the coil, one is still allowing the inductance to occur and not diminishing he cause of the voltage spike itself and if the trigger wire above the diode is near the relay, inductance can still cause a spike up the trigger wire. Using those assumptions, I was under the impression that killing the spike by going across the coil was all that was needed.

Quote:
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The cap is to smooth the PWM signal to the point at which coil sees it as a constant current source and not a square wave.
yeah, I know that's it's primary purpose but when I was reading about wiring for such, it stated that caps also act to regulate voltage and diminish the effect of spikes

Either way probably works fine in nearly every situation. Apparently the CanBUS has it's own protection because of there are a multitude of electrical interferences present in automobiles that cause cause inductance spikes and they had to build in protections for it
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