identifying pcb component

Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=140452
Printed Date: May 10, 2025 at 2:21 AM

Topic: identifying pcb component

Posted By: 156srt
Subject: identifying pcb component
Date Posted: December 30, 2015 at 10:02 AM

Hi, I'm Paul, I'm new to this forum, I was directed here by someone at an electronics store who had no idea what this component is, could someone here please identify this component? I've tried googling it but to no avail!
The board itself is for converting analog 12v to w-bus protocol signals (similar to CAN-bus and OBD2) for a webasto heater for a car. I'm not a wizard with electronics (it was pre-made) especially when it comes to CAN-bus and protocols!
Any ideas as to what it is and where I can get a replacement would be gratefully received!!
Thanks for your time.
Paul.

posted_image

Replies:

Posted By: i am an idiot
Date Posted: December 30, 2015 at 10:07 AM

It is a reverse polarity protection diode. It's purpose is to protect your device in the case of somebody connecting the battery backwards. Is it shorted? Does the device blow a fuse as soon as you put it in or apply power to the unit?

You can replace it with a non surface mount device if you like. 1n4001 or equivalent.

Posted By: 156srt
Date Posted: December 30, 2015 at 6:02 PM

i am an idiot wrote:

It is a reverse polarity protection diode. It's purpose is to protect your device in the case of somebody connecting the battery backwards. Is it shorted? Does the device blow a fuse as soon as you put it in or apply power to the unit?

You can replace it with a non surface mount device if you like. 1n4001 or equivalent.

Hi, thank you very much for that, no one I spoke to had any idea what it was.
Well, it makes sense, hopefully works too, because, to my embarrassment, I actually connected the wires wrong, in the dark and in a rush... Hopefully lesson learned!
Does it matter which way the replacement is fitted?
Thanks very much once again!
Paul

Posted By: howie ll
Date Posted: December 31, 2015 at 2:56 AM

Yes very much so! Hence reverse polarity protection. The diode acts as a fuse and blows to save the board.
Looking at the board, band side of diode to left.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Posted By: 156srt
Date Posted: December 31, 2015 at 3:44 AM

Thanks for that howie, probably another disaster averted!