H7s for high and Low Beam yield different light. Why?
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H7s for high and Low Beam yield different light. Why?
It says in the owners manual that the low beams and high beams use the same H7 Halogen bulb. However, turn on the low beams and add the highs and inspect the vehicle from the front of the car...
Clearly, the high beams burn MUCH, MUCH brighter than the lows. Why is this? Are the Highs operating at the full 55W while the Lows are "stepped-down" to a lower wattage level? IMO, the difference in light level is immense, and can't be attributable to the size of the reflector housing alone.
I ask this question, because there has been discussion about using over-watted bulbs in the low beams, and concerns some have for potential damage to the wiring, reflectors, etc. However, some members (Chatmanr, among others) have been running 80W Phillips Rallye bulbs for more than a year without any visible damage at all.
Is it possible that the Low beams actually power the 55W H7 bulbs with less wattage than 55W to make them dimmer than the Highs? If so, then I would think that "over-watted" bulbs would be similarly cut-back... minimizing the chance of damage by using higher wattage bulbs in the same housing.
Help me understand, please?
PS, Yes, I have the Rallyes on order, along with the Vision Plus's. Powerbulbs.com stocks both.
Clearly, the high beams burn MUCH, MUCH brighter than the lows. Why is this? Are the Highs operating at the full 55W while the Lows are "stepped-down" to a lower wattage level? IMO, the difference in light level is immense, and can't be attributable to the size of the reflector housing alone.
I ask this question, because there has been discussion about using over-watted bulbs in the low beams, and concerns some have for potential damage to the wiring, reflectors, etc. However, some members (Chatmanr, among others) have been running 80W Phillips Rallye bulbs for more than a year without any visible damage at all.
Is it possible that the Low beams actually power the 55W H7 bulbs with less wattage than 55W to make them dimmer than the Highs? If so, then I would think that "over-watted" bulbs would be similarly cut-back... minimizing the chance of damage by using higher wattage bulbs in the same housing.
Help me understand, please?
PS, Yes, I have the Rallyes on order, along with the Vision Plus's. Powerbulbs.com stocks both.
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C230
Might be that the difference between high and low (or regular and dipped) on most cars is the low side has a horizontal cutoff. Theoretically the light levels should be the same but the dipped beam should not direct as much light above horizontal.
But I suppose it could be possible to run the Lows at a lower voltage.
But I suppose it could be possible to run the Lows at a lower voltage.
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lhoang, I've not seen the Rallye's myself, but from Chatmanr's posts, I understand it's pure white light, like the Vision Plus, just more of it... not the Xenon (blue tint) look...
R4ND0M_AX3, if you look into the low beams from below bumper level, you can see a physical horizontal shelf, blocking the light from projecting higher than this cutoff point. My theory is that the Vision Plus bulbs keep the same physical pattern, but that the extra light carries further down the road simply because there is more intensity in the beam. By extension, the Rallye's should be even more intense.
R4ND0M_AX3, if you look into the low beams from below bumper level, you can see a physical horizontal shelf, blocking the light from projecting higher than this cutoff point. My theory is that the Vision Plus bulbs keep the same physical pattern, but that the extra light carries further down the road simply because there is more intensity in the beam. By extension, the Rallye's should be even more intense.
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From: Canada
05 CLK 500 cab
If the bulb is manufactured for 55W, I think the only non-optical way to decrease the light intensity is to step down the voltage. I don't have my car yet, so I can't check, but it is possible that the voltage to the low beams has been stepped down somewhat to increase the bulb life. Other car makers (e.g. Volvo) do this. It should not need to be decreased to the point where there is a visible difference to the output, but one never knows.
The obvious way to check is to put a voltmeter on the high and low beam sockets.
The obvious way to check is to put a voltmeter on the high and low beam sockets.
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From: Ohio
2010 C300 4matic
I have been running 100W low beams for about two months now and have had no problems yet. I know there is a risk, but I am hopeful that they will be okay for at least the term of my lease.
MB-BOB, I put similar 100W bulbs in a friend's C240 and he had to lower the lights before he was happy with the light they were putting out. In my coupe, I actually had to raise the lights. For some reason, the sedans must have the lights aimed much higher. I was very dissatisfied with my low beams stock. The higher wattage bulbs and raising them works well for me.
BTW, I am using Eaglite bulbs from midnightmoose.com. They are pretty white, with a hint of blue, and they are only 15.50 a pair. Philips bulbs might be more white or put out more light, but they cost a lot more also.
MB-BOB, I put similar 100W bulbs in a friend's C240 and he had to lower the lights before he was happy with the light they were putting out. In my coupe, I actually had to raise the lights. For some reason, the sedans must have the lights aimed much higher. I was very dissatisfied with my low beams stock. The higher wattage bulbs and raising them works well for me.
BTW, I am using Eaglite bulbs from midnightmoose.com. They are pretty white, with a hint of blue, and they are only 15.50 a pair. Philips bulbs might be more white or put out more light, but they cost a lot more also.
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From: Ashburn, VA
'19 GLC 300, '19 TM3SR+
High beams are shaped differently compared to lows. They are supposed to illuminate the road farther away from the vehicle and - unlike low beams - they have no horizontal cut-off. Try the same trick, but position your head closer to the ground to catch the hot spot of the low beams. You'll see that they are plenty bright.
As for Volvos using reduced voltage for the lows - they were forced to do that not so long ago as a countermeasure against bulbs burning out way too often.
As for Volvos using reduced voltage for the lows - they were forced to do that not so long ago as a countermeasure against bulbs burning out way too often.
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From: Lower Mainland, British Columbia, Canada
'00 ML320 Elegance/'03 C320 4-matic
It's all optics, that's all. Same bulbs, and same 55 watts. The halogen based low beam DRLs do run at reduced intensity though (85% of full illumination)
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the difference in light output is due to how the reflector and the plastic lens bend/shape the light. both bulbs are burning at the same wattage. a good example of this is a maglite. when you turn the head one way it is very bright and focused but when you turn it the other way it is ver broad and doesnt seem as bright.
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Originally posted by lars
The obvious way to check is to put a voltmeter on the high and low beam sockets.
The obvious way to check is to put a voltmeter on the high and low beam sockets.
If it's true that US vehicles run at decreased voltage when programmed in DRL mode, I assume there is circuitry in the car to make this happen. This makes it possible that the standard Lows and Highs run at different wattage levels.
I completely understand how reflectors focus the light. But, no matter what angle I look at them, the Low Beams are noticeably darker than the Highs. I would like to confirm the standard voltage running across each socket, with and without DRL settings.
Last edited by MB-BOB; Nov 21, 2002 at 03:18 PM.
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From: Gaithersburg, MD
2002 C240 6-spd (ret)
Originally posted by MB-BOB
If it's true that US vehicles run at decreased voltage when programmed in DRL mode, I assume there is circuitry in the car to make this happen. This makes it possible that the standard Lows and Highs run at different wattage levels.
If it's true that US vehicles run at decreased voltage when programmed in DRL mode, I assume there is circuitry in the car to make this happen. This makes it possible that the standard Lows and Highs run at different wattage levels.
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Good, Mark, we're on the same page. Now all we need is someone to measure the various settings. I'd do it, but I don't have a proper 12-volt multimeter, and I'm not going out to buy one. I still hoping for a digital camera for Christmas. How 'bout you? LOL!
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From: Gaithersburg, MD
2002 C240 6-spd (ret)
Originally posted by MB-BOB
Good, Mark, we're on the same page. Now all we need is someone to measure the various settings. I'd do it, but I don't have a proper 12-volt multimeter, and I'm not going out to buy one. I still hoping for a digital camera for Christmas. How 'bout you? LOL!
Good, Mark, we're on the same page. Now all we need is someone to measure the various settings. I'd do it, but I don't have a proper 12-volt multimeter, and I'm not going out to buy one. I still hoping for a digital camera for Christmas. How 'bout you? LOL!
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'01 C240/6
I'm not sure I understand your question, but normally a halogen high/low headlight bulb has 2 filaments in it. When the low beams are on, only the low beam filament is on. When the high beam is activated, the high beam filament is activated.
That's why there are three prongs going into a high/low headlight.
That's the way it is on, for example, H4s on BMWs, Porsches, etc.
That's why there are three prongs going into a high/low headlight.
That's the way it is on, for example, H4s on BMWs, Porsches, etc.
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From: Ohio
2010 C300 4matic
SoCal, the highs and lows are two different bulbs in these cars. The low is in the big circle part of the housing. The highs are in the smaller circle part of the housing. But I do know some types of bulbs are the way you described. Someone I know just got some for a 300E. They were 80W/100W in the same bulb for lows and highs.
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'01 C240/6
Thanks.
On older cars with 4 headlights, the inner lights are usually the dedicated high beam - they only go on when the high beams are activated. But, the outer large lights are usually low AND high beams. So when the highs are activated, the dedicated inner high beams go on, AND the outer lights get brighter, too (by way of a dual filament).
So what you are saying is that on a C, when you activate the high beams, the low in the big circle part of the housing does not get brighter? Only the smaller inner high beams go on?
On older cars with 4 headlights, the inner lights are usually the dedicated high beam - they only go on when the high beams are activated. But, the outer large lights are usually low AND high beams. So when the highs are activated, the dedicated inner high beams go on, AND the outer lights get brighter, too (by way of a dual filament).
So what you are saying is that on a C, when you activate the high beams, the low in the big circle part of the housing does not get brighter? Only the smaller inner high beams go on?
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Originally posted by SoCal240/6
So what you are saying is that on a C, when you activate the high beams, the low in the big circle part of the housing does not get brighter? Only the smaller inner high beams go on?
So what you are saying is that on a C, when you activate the high beams, the low in the big circle part of the housing does not get brighter? Only the smaller inner high beams go on?
On my C320, (and your C240... and the Coupe) the outer bulbs burn on LOW Beam at all times. The smaller, inner lights burn HIGH Beam only, and only come on when activated via the turn stalk.
The Manual says they use exactly the same H7 bulb. I will not pull them out to confirm until my new bulbs arrive, but the pictures of the replacement Phillips bulbs show them as having only two prongs.
Dozens of members here have already replaced their bulbs. Maybe one of them can clear this up...
Turn on the LOWs and add the HIGHS, and compare the light levels from both, side by side. They are vastly different in light intensity. Something in the circuitry causes these identical bulbs to burn at different intensities, based on their location in the housings.
Last edited by MB-BOB; Nov 21, 2002 at 08:42 PM.
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2002 C240
Originally posted by MB-BOB
The Manual says they use exactly the same H7 bulb. I will not pull them out to confirm until my new bulbs arrive, but the pictures of the replacement Phillips bulbs show them as having only two prongs.
Dozens of members here have already replaced their bulbs. Maybe one of them can clear this up...
The Manual says they use exactly the same H7 bulb. I will not pull them out to confirm until my new bulbs arrive, but the pictures of the replacement Phillips bulbs show them as having only two prongs.
Dozens of members here have already replaced their bulbs. Maybe one of them can clear this up...
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From: Ohio
2010 C300 4matic
MB-BOB, they are in fact the exact same bulbs for the high and low beams, and you can already see the pics above that there are two prongs. I replaced both of them, 100W lows and 55W highs. But the high beams are still brighter, I guess just because of the reflectors. I don't know for sure.
