# HID Return Wire - Remove Insulation?



## twentysixtwo (Jan 2, 2005)

On the return wire of an automotive HID bulb, there's a thick insulation that makes the return wire block off 3-4 times as much light.

What would happen if I were to remove this with an exacto knife (or at least shorten it to aft of the discharge envelope)

The goal is to minimize the shadow of the return wire in the beam.....


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## Sway (Jan 2, 2005)

I don't think thats a good idea the insulator is there for a reason to stop high voltage arcing. A missing or broken insulator equals a blown bulb sooner or later.

Later
Kelly


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## Draco_Americanus (Jan 3, 2005)

I too have thought about removing that ceramic insulator on the return wire but I side with Sway. That 25kv starting pulse can have good habit of finding other ways to ground so I would not make it any easier for that to happen.


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## MaxaBaker (Jan 3, 2005)

This comes to mind, well, not that big /ubbthreads/images/graemlins/grin.gif -- http://www.hnd.usace.army.mil/pao/CEAInfo/Explosion%20Photo.JPG
Trust me, it's not a good idea /ubbthreads/images/graemlins/mad71.gif /ubbthreads/images/graemlins/tongue.gif


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## twentysixtwo (Jan 4, 2005)

Well......I guess I'm not that worried about it. I'm thinking it's designed as insurance that it won't short against a glare shield, etc. More importantly, I had access to a couple of HID bulbs so I tested it out. 

I took a damaged D1R and stripped all the insulation from the return wire by carefully crushing it with a pair of needle nose pliers. Plugged it in and it did a quick "Click-click-click-click" but did not start. Damn, I just realized I should have checked to see if the bulb worked to begin with. The base is cracked all the way around, so I don't know if it's that or the stripped insulation which is the culprit.

OK. I take a used D2R and check to see that it does work. I then remove the top centimeter plug it in....KABOOOOM!!!!

Seriously though, the bulb lit, no problems whatsoever. I then crushed the next centimeter and it still worked fine. I finally crushed it all the way down to the base. I didn't want to leave the wire exposed with the base metal mount adjacent so I left the last centimeter that is in the base. Still worked fine. 

Some crude calculations:

The wire is about 8.5 mm from the center of the bulb. The return wire is les than 0.5 mm thick. The Ceramic insulation is at least 2 mm thick. If we model the lamp as a point source radiating with a infinitely long return wire, the insulation blocks 2/(2*3.14159*8)% of the light while the bare wire blocks 0.5/(2*3.14159*8)%.

Doing the math, the insulation blocks 4% while the wire blocks 1% so removing the insulation will give you a hair over 3% more light. In addition, that shadow is just plain ugly.

What's next? I'm going to try a D1 style bulb. I will have to find something that is nonconductive and highly heat resistant to keep the last bit of insulation in the base (Plumbers Putty?) I don't want the thing to slide to the tip of the wire and have a vibration or problem cause a short.....


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## MaxaBaker (Jan 4, 2005)

Well.....I woudn't keep it without insulation for long. My step brother tried this with his HID car headlites and that managed to completely destroy the reflector behind the bulb and cracked the lens in front of it on one of them. I do not know if arking electricity was the exact cause of the explosion or a different problem, but all I know now is that I have to buy him another D2S bulb because I was the one who told him to try it. /ubbthreads/images/graemlins/mecry.gif


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## twentysixtwo (Jan 4, 2005)

What kind of car was it and was the HID factory spec? When you say it cracked the lens, was it micro cracking (small cracks) or big cracks? When you say destroy the reflector, do you mean melted? Very interested in the details. I'm planning to throw this in my THOR.....Thanks,


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## MaxaBaker (Jan 4, 2005)

1970 Monte Carlo

I have no idea bout the factory specs, he bought them and installed; I suggested that he try to remove it, that's all

It was 2 large parallel cracks

The reflector was, how do I put this, "shattered" part of it; no melting that I noticed, it is odd

I am not say you can't do this; he did it to his other light and it seems fine so far. Again, he is no expert at this and there are any number of other factors that could have done it. It seemed to have been a 1 time thing(hopefully /ubbthreads/images/graemlins/icon15.gif) and it may work fine for you, just BE CARFULL!! To give more detail, the "explosion" was kind of like a high powered flashbulb explosion.

Hope that helps /ubbthreads/images/graemlins/cool.gif

C ya,
Baker


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## twentysixtwo (Jan 4, 2005)

Thanks for the info. Interesting. A 1970 car would be prior to the removable bulbs, so I assume the HID is in some sort of sealed beam replacement? Was the HID bulb was shattered as well? 

The Thor metal reflector is probably safe if something goes wrong, but I don't know how strong that front lens is....


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## MaxaBaker (Jan 5, 2005)

I don't know if it was a sealed beam HID light (never heard of that actually /ubbthreads/images/graemlins/thinking.gif) but he has done so much stuff to that car he could have done anything. If he really wanted to I suppose he could have ripped the existing light out ( entire thing; bulb, reflector, lens) and thrown in some other light system that was from a jag or something. I'll try to find out for you.


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## Draco_Americanus (Jan 6, 2005)

One well know failer mode for HID bulds is for them to explode! and some times with some force, tis why it's not wise to stare at a naked bulb. (some say it's unwise to stare at any thing thats naked unless your married to it. ) /ubbthreads/images/graemlins/jpshakehead.gif


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