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Old 11-20-2012, 11:38 PM
Doktor Bert's Avatar
Das Sturm Uberdoktor
 
Join Date: Jan 2005
Location: Palm Springs, CA.
Posts: 2,670
W116 Headlamp Switch Go Boom:

Recently, my headlamps have been 'lazy' on cold mornings. Tonight on I-10 in Redlands my low beams went out. The switch was hot to the touch and all fuses were intact.

Flash to pass function still worked, but I ran a jumper from the park lamps to the low beams to get the car home.

Where could I get a replacement in So Cal tomorrow?????

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #2  
Old 11-21-2012, 08:54 AM
Doktor Bert's Avatar
Das Sturm Uberdoktor
 
Join Date: Jan 2005
Location: Palm Springs, CA.
Posts: 2,670
Waiting for first light this morning to drive in to work. I will seek a replacement today....
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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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  #3  
Old 11-21-2012, 09:46 AM
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Join Date: May 2007
Location: Out in the Boonies of Hot, Dry, Dusty, Windy Nevada
Posts: 9,585
I was in the carson city yard last mo and they had 2 116 in the yard. I`ll pull one/both if you want in a couple days when I get there. leaving this morning for there. HMMM...... doesn`t help you now.

Charlie
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there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works
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  #4  
Old 11-21-2012, 09:58 AM
scottmcphee's Avatar
1987 w124 300D
 
Join Date: Mar 2008
Location: Edmonton, Canada
Posts: 1,539
You can keep your next switch alive forever, by adding a relay to power the lamps rather than running the high current through the headlight switch contacts. Just use the switch to power the relay coil, and move the high current path through the relay contacts.

The problem happens when switch contacts begin to degrade, they increase resistance at the resting point of contact. Increased resistance creates more voltage drop *at that point*, which amounts to power waste (heat) at that point. This cycle keeps up until the switch starts consuming more power than the headlights as you are effectively making a little resistive heater in there. (100 Watts is a lot of heat to balance on this power split between the headlights and switch contact heater - next time you grab a 100W bulb see how long you can hold on!).

Not to mention your headlight voltage is dropping as this carries on over time, getting dimmer and dimmer... even with new bulbs. At some point of wear you'll get a sizzle.. melting plastic, fried contact for sure, some smoke, maybe a little fire, and a switch to replace.

You only need very little current through the switch contacts to power a relay coil. Those contacts are so overkill for switching a small coil, they'll last forever. Even if you don't put a flyback diode or snubber on the coil.

If in your lifetime the relay contact degrade, you can pop a new one of those into its socket for $5, in 1 minute. Versus changing a headlight switch again, that will be harder yet to find.

FYI - I located my relays up hear the headlights to keep the high current run very short, because there's voltage drop between the switch and headlight due to wiring constriction (limits current). And I made a direct power run from battery (fused) to those relays using a very heavy gauge wire (like 10AWG).

Brightest bulbs around! They're getting slightly over-rated voltage this way. Most auto headlight bulbs are rated at 11.7v or so, something lower than battery/charge limits... They do this to accommodate normal wiring constraints and voltage drops just mentioned. Give these bulbs a full shot of just a half volt more than they're expecting and you'll see noticible brightening!

For me, headlights are the most critical safety component for getting to my destination at night, in the winter, at -40C... you don't want to stop anywhere other than a warm garage. Every other electrical thing on my car can stop working for all I care (and this could happen!) so long as the headlights shine and that diesel remains turning over... I'm getting home.
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Cheers!
Scott McPhee

1987 300D

Last edited by scottmcphee; 11-21-2012 at 10:24 AM.
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  #5  
Old 11-21-2012, 02:34 PM
Doktor Bert's Avatar
Das Sturm Uberdoktor
 
Join Date: Jan 2005
Location: Palm Springs, CA.
Posts: 2,670
Charlie,

Thank you very much. I can have one by Monday brand new from MBZ dealer for $84.00 my cost. I will rig up something after work tonight as a temporary fix.

Scott....You are right!!!! MBZ should have done this!!!!!!

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Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership
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