Diode in trunk bulb housing??

dogger37

Veteran Member
Joined
May 28, 2012
Location
PA
TDI
2012 passat
Accidentally grounded out my rear trunk light and burned up the diode that is beside the bulb. Just wondering if anyone can tell me what size of diode it is so that I can replace it? Also why is it there?
Pictures would also help me identify the correct diode
Thanks,
Donny
 

Vmwalker

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Joined
Jul 20, 2011
Location
Gahanna, Oh
TDI
2013 Passet TDI SEL Premium Reflex/Moonrock
Make sure the replacement diode is installed oriented the same direction as the defective diode.
 

vw_norm

Gone, but not forgotten.
Joined
Jul 22, 2012
Location
Hawaii
TDI
2012 NMS TDI SEL Platinum Gray w/moonrock
Officially, it is a 1N4004 diode. Rated at 1 Amp. When installed in this manner in parallel with a load, such as a lamp, it functions as what is known as a 'flyback' diode, which helps to reduce the voltage arc across the contacts of a relay by helping to dissipate the current that will try to flow across the contacts of the relay as they open or close. Suppressing this arc will improve relay contact life.
Pay attention to the white or silver stripe on the replacement diode. In my B7, the band was installed to the rear. Now that I popped open one of my lenses to look at the diode, I cannot get the darn thing to stay on. It came off easy enough, but no matter what, it will not stay locked on the door panel. Probably got to use a smidgen of silicone, but I don't think that should be necessary. Let me know if you can get yours to stay on.
 

compu_85

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Sep 29, 2003
Location
Springfield VA
TDI
... None :S
norm, I had the same problem with getting the lens to stay on. Pry the lamp housing out from the door just a bit, the back edge of the lens needs to hook around the housing and the door card gets in the way.

-J
 

Dr speed

New member
Joined
Jul 28, 2012
Location
Md
TDI
2012 b7
Had the same issue with the kit from ECSctuning. Had Oscar look at the diode for me in his housing and it was 1N4007 made by MMC. Are you guys physically looking or going off old B5 specs?
 

fredthe

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Jul 18, 2012
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Bowie, MD
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2013 Passat SEL Premium DSG, 2015 Golf Sportwagon SEL DSG
The only difference between a 1N4004 and a 1N4007 is voltage; 400 vs 1000 volts. Either should work, if the spec says 1N4004 that would just be a minimum, 1N4005, 6, or 7 would work. Use whatever you can get your hands on.

Manufacturer really doesn't matter, this is a very generic part that has been around for longer than I'd care to admit :)
 

vw_norm

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Joined
Jul 22, 2012
Location
Hawaii
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2012 NMS TDI SEL Platinum Gray w/moonrock
I popped the lens and took the number off the diode installed in my B7. fred is right about the specs, any old diode will work, but for 12 V, going to 1000V is overkill. All you're trying to do is quench that arc across the contacts of the relay so it doesn't burn up prematurely.
 

dogger37

Veteran Member
Joined
May 28, 2012
Location
PA
TDI
2012 passat
Thanks everyone for their help and support! It is nice to know that there are still good people in this world
 

TomB

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Joined
May 1, 2003
Location
Cle Elum, Washington/Las Vegas, Nevada
TDI
2015 Audi TDI Prestige Sport
I popped the lens and took the number off the diode installed in my B7. fred is right about the specs, any old diode will work, but for 12 V, going to 1000V is overkill. All you're trying to do is quench that arc across the contacts of the relay so it doesn't burn up prematurely.
It might only be a 12V system but the spike can be higher voltage if I am not mistaken.
 

vw_norm

Gone, but not forgotten.
Joined
Jul 22, 2012
Location
Hawaii
TDI
2012 NMS TDI SEL Platinum Gray w/moonrock
norm, I had the same problem with getting the lens to stay on. Pry the lamp housing out from the door just a bit, the back edge of the lens needs to hook around the housing and the door card gets in the way.

-J
Thanks for the tip - as I was prying (not too gently), the entire housing popped out of the door. I was able to securely snap the lens back into place and then pop the housing with lens attached back into the door. problem solved!
 

vw_norm

Gone, but not forgotten.
Joined
Jul 22, 2012
Location
Hawaii
TDI
2012 NMS TDI SEL Platinum Gray w/moonrock
Which relay controls the trunk light?
There is not a relay per se, but it is controlled by the CECM (central electric control modules; aka BCM - body control module), which turns on the trunk light after the switch in the latch assembly makes the connection to ground. The BCM is the master controller for most things electrical in the car and is located under the dash above your left foot. It has three large connectors attached to it.

 
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