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Old 08-18-2000, 12:09 AM
Registered User
Join Date: Apr 2000
Location: Minnesota
Posts: 92
I ve been using the PIAA superwhite plasma H4 100/110W for almost 8 month now....oh i forgot said they are different one. you see these light burn out about every 3 months and is killing my wallet. my question this normal?! Is it because over voltage?! If I use normal 55/60w PIAA super white or any other white bulb would that last longer?!
Before i use some cheap 100/110w they burn out ever, i switch to the best PIAA and it is still the same....can anybody help me. I try the SEARCH, but nobody seems to talked about this MAX life of these bulb.
thanx =)
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Old 08-18-2000, 12:33 AM
Posts: n/a

I'm not an expert on the topic but have been researching lighting additions for one of my cars and found that higher wattage bulbs (over the rated capacity for standard light fixture) suffer due to a couple of reasons: 1) the wiring harness does not deliver enough voltage to properly drive the lights because the wires are too small for the bulbs and not permit enough voltage/amperage to reach the bulbs. Running the bulbs under their power requirements will cause them to not light up as brightly as they are made to do. According to what I've read this reduces the lifetime of the bulb; 2) The excess heat buildup can also shorten the bulb's life and cause a meltdown in the lighting fixture and/or wiring harness and/or fuse box, and/or lighting switch. The most susceptible in this list to meltdown will go first!

The solution that was recommended to me, and what I'm planning on doing is to run a separate wiring harness rated for the wattage of the bulbs I want to use to the lights, and use a different switch for turning these on and off, plus using a relay so that the switch doesn't have to take the full brunt of the voltage. I was also told to have relay secton of the the light switch run through the ignition so that I don't inadvertently leave the lights on when I park the car (which I've done before with another car)!

Lastly, someone told me that the hella bulbs are longer lived than the PIAAs, FWIW.


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Old 08-18-2000, 08:16 AM
Posts: n/a

I hope that when you say that you are going to run the "relay" section of your circuit through the switch, that you are talking about the coil side of the relay and not the contact side. The coil side will have minimal current draw.

Fabricating a high current wiring system with relays and heavy wire will indeed protect the wiring of the vehicle and should be considered absolutely mandatory if you're going to use 100W bulbs. However, by decreasing any wiring resistance, the voltage at the bulb will increase, which will decrease bulb life. The wiring beef up will not extend bulb life, it will probably slightly decrease it, while it is increasing light output. If this were an inductive load such as a motor, lower voltage would decrease it's life, with a bulb, however, it's life is strictly determined by heat dissipation. If there is more voltage AT THE BULB, there will be more heat to dissipate. This will also, obviously, create more heat within the lamp assembly.

I bought a parts car with European lights which I then put in my driver. They had 110Watt bulbs in them, and smelled of high heaven with a burnt electrical smell. I put 55/60's in them and they work great. The shape of the beam has as much to do with light output as the wattage of the bulb. That's why Euro lights are so much better.

If you had some data on the different types of light bulbs, which would tell you the percentage of energy which generates light, and the percentage of energy generating heat, you could probably derive which bulb type could be tolerated with the least amount of heat dissipation.

Good luck,

Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles
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Old 08-18-2000, 09:58 AM
Registered User
Join Date: Sep 1999
Location: San Antonio, Texas, USA
Posts: 154
Heat build up is the problem. One common problem along that line is true of head lamb bulbs of all wattages and wiring: Always be sure to NEVER touch the bulb with your bare skin.
The least little bit of oil (fingerprint) will darken from the heat, absorb and concentrate heat at that point, interfere with heat dissapation, and contribute to if not cause early bulb failure. Thats why the directions with the bulbs warn against handling 'em with bare hands.
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Old 08-18-2000, 10:34 AM
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Join Date: Apr 2000
Location: Minnesota
Posts: 92
I understand that you should never touch the glass part of the bulb, that's why i wear glove when puting the lights in for all the
bulbs i put in. Is the same thing 2-3 months max!! If these stupid whit or blue give me so much trouble, might as well swith them back to reg. 55/60w another question is if i do switch back, is there any light out there that is little bit brighter? thanx everybody!
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Old 08-18-2000, 12:28 PM
Posts: n/a

Thanks for the articulation. I'd heard that bulbs are designed to run at a certain voltage and running them under or over their rating will significantly shorten their life. Again, I claim no expertise on this topic - just relaying (sorry about the pun) what I'd heard.

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Old 08-18-2000, 03:57 PM
Posts: n/a
Here's some insight on the bulb life --
Heat, voltage, amperage, and resistance are all factors in the bulb's life.

1. Heat increases exponentially inside the reflector as the wattage is increased. The reflector is designed for a 50-65 watt bulb, but could handle about 80W without stressing the limitations, 110W is just too hot.

2. This brings us to another point, resistance. Resistance increases as the heat increases, thus altering the voltage/amperage requirements from the normalized draw outside the enclosure.

3. Voltage drops and amperage increases under these circumstances create stress on the filament, thus it fails pre-maturely.

These 100-110W bulbs are marked 'off-road use only' for a reason. They are designed to be used in a specific 'larger' (sometimes ventialted) housing, and are for short-term useage. Long-term use in a standard, sealed housing will produce the short life-span that you are experiencing.

I suggest you stick with the recommended wattage bulbs (50-65), or move up to the median wattage of 60-85. These mid-range bulbs are available from Hella and will last almost as long as the recommended bulbs. The output is much better than the 50-65W, but is not really noticeable as compared to the 100-110W bulbs.

I am not sure about where to get them, but I know somebody sells the 60-85W 'upgrade' Hella bulbs, I've bought them. Look around and you should find them. Price is around $10.00 each.

Good Luck,

76 240D (W115) - 550K miles
78 300D (W123) - 200K+ miles

[This message has been edited by WmHarlow (edited 08-18-2000).]
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Old 08-18-2000, 05:38 PM
Registered User
Join Date: Jan 2000
Location: Fl
Posts: 140
I have had a set of piaa super white 9004 in my 300E for a little bit more than a year know and are still glowing. Maybe you just need to use the right wattage, and avoid the complications.

Good luck

My $0.02

'86 300E
'87 300SDL
'92 190E 2.6
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Old 08-19-2000, 02:03 PM
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JCE JCE is offline
Down to the Wear Bars
Join Date: May 1999
Location: So Kalifornia
Posts: 2,189
I switched to Euro lights and got a much better, more usable beam pattern. I then replaced the 55/60 watt H4 with "Hella H4+30" redesigned H4 bulbs, part 78150, which have the same wattage but a slightly redesigned filament and a trace of xenon gas for "30% more light" and less scatter. Noticable improvement again, with a slightly whiter light. My next step will be to install the 10 guage wire and relays described in the star article and at Susquahanna Motor Sports home page . (I bought the Hella bulbs here as well.)
This should minimize resistance to the bulbs and let them run at full potential. By the way, I replaced the fog H3 bulbs with the Hella coated 55 watt H3 bulbs, part 78136Y. This gave me fog lights that appear white when the lens is viewed from the front of the car, but the light on the road is yellow! I drive with my fog lights on in marginal wheather, and had no problem with oncoming drivers when the beams were yellow on the stock headlights. However, when I changed to Euro lights, the fog lamps were white, and since they are located next to the headlight, oncoming drivers sometimes would flash me to dim my lights. There is enough yellow on the road with the Hella units that the oncoming drivers no longer flash their high beams at me. Hope this helps out.

87 300E, 65k miles
Smoke Silver
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Old 08-19-2000, 03:37 PM
Senior Canadian Member
Join Date: Jul 2000
Location: British Columbia, Canada
Posts: 827
In addition to what everyone said about the wiring harness not being able to deliver sufficient power to the lights and heat build up, you'll want to reconsider using 100/110W bulbs.
Plain and simple they are too bright and a hazard to other motorists.

It can take up to a 1/2 an hour for a person's night vision to re-adjust after lighting a cigarette in the dark. With that kind of candlepower, not only could you accidently damage someone's eyes, but you could also cause an accident.

the only time you'll need lights that bright is when you're running in pitch black at over 80 mph.

Downgrade to something like 55/65. They're plenty.

A simple test is to stand in from of your car and to the side, roughly where someone in the oncoming lane would be...stand back about 50' or so, then have a friend switch on the lights. This would simulate you turning from a cross street and the light bems cutting trhough your field of view...I promise you it's not pleasant.

Better yet, have someone drive your car past you (make sure you're crouched at roughly the same height someone sitting in a car would be. Then you can see what happens when the distance closes.

Don't forget, just because the lights aren't pointed directly at someone, the "wash" could still impair their vision.

Drive safe


Yen-Hsen Liem
'93 500E black pearl/black leather; 89,000km; 245/45-ZR17 Michelin Pilot SX; 17x8.25 factory EvoII
'93 500E bornit(blackberry)/black leather; 69,000km; european delivery; 245/45-ZR17 Michelin Pilot SX; 17x8.25 factory EvoII
'88 560SL desert taupe/dark brown leather; 89,000km; Euro headlights
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