fog relay/ oem momentary switch
Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=111776
Printed Date: May 20, 2024 at 9:37 PM
Topic: fog relay/ oem momentary switch
Posted By: themodifier
Subject: fog relay/ oem momentary switch
Date Posted: February 20, 2009 at 4:20 PM
Newbie here. Very 8D and informative site. Looking for a little help with installing my fog lights on my 99 Silverado. I've attached a link of the factory wiring diagram. https://il88.photobucket.com/albums/z64/IMI4tth3w/foglightelectricaldiagram.gif I am attempting to bypass the BCM(body control module). I believe that I need to install a "Latched on/off" relay(as noted on this site).https://www.the12volt.com/12voltimages/latchonoffspnd.gif I am not sure if this is correct, because it appears that the factory relay is receiving a negative ground input from the bcm, and the latching relay would be providing a positive input according to the diagram. Any ideas on how to properly accomplish this would be greatly appreciated. BTW, I would prefer to not use diodes.
Replies:
Posted By: themodifier
Date Posted: February 24, 2009 at 7:17 PM
I would assume by the lack of response, it is impossible to convert a negative pulse into a constant negative output via relays?? 
Posted By: Ween
Date Posted: February 24, 2009 at 7:26 PM
hi, the link doesn't work (at least for me). and yes, you can convert a negative pulse to a negative output with a latching relay. do you need to have a negative output? an old VW headlight relay will do what you are trying to accomplish although with a positive output. the relay is rated for 150W, good enough for two fog lights (55W bulbs of course) m running with sissors 'cause i can
Posted By: ckeeler
Date Posted: February 24, 2009 at 7:48 PM
themodifier wrote:
I would assume by the lack of response, it is impossible to convert a negative pulse into a constant negative output via relays??
it is absolutely possible. you are not getting much response because your link does not work.
Posted By: themodifier
Date Posted: February 24, 2009 at 11:06 PM
Not sure what happened with the link. Let me try it again.
I need to convert a negative pulse from my factory momentary switch to the factory relay which requires a constant negative signal. My objective is to use factory components, but eliminate the BCM. Once again, I thank you in advance for your assistance and input.
Posted By: themodifier
Date Posted: March 02, 2009 at 1:03 PM
Any ideas?
Posted By: ckeeler
Date Posted: March 02, 2009 at 8:01 PM
Posted By: themodifier
Date Posted: March 02, 2009 at 10:32 PM
Thanks for the reply. Just to be clear, the purple output in your diagram is constant negative, right? If I understand, the relay on the right will stay energized until either ground or 12v(+) is removed, right? If so, I need to see if there are other options with more relays. I need to have the ability to engage and disengage the latched output with a single pulse from a switch. The first pulse from the switch will engage the latch. The next pulse from the switch will disengage the latch. If at all possible, I would prefer not to use a diode as noted in the diagram you provide. Thanks again for all the help!!
Posted By: ckeeler
Date Posted: March 03, 2009 at 8:43 AM
have you looked in the "relay" section at the top of the page yet? im assuming you are not getting many replies because there are already diagrams there to do just what you are wanting (provided you are willing to use 6 relays because you dont want to use any diodes). either that or purchase an electronic latching relay.
Posted By: ckeeler
Date Posted: March 03, 2009 at 8:49 AM
Posted By: themodifier
Date Posted: March 03, 2009 at 2:15 PM
Yes I have. Please take a look at my original post, and you will see that I referenced the latching relay from this website 
This set-up will not work, because the output is a constant 12v+(as noted in BLUE), and I need 12v- constant output. I appreciate your input, but I don't see a solution. Is there something I'm not understanding? Thanks in advance
Posted By: ckeeler
Date Posted: March 03, 2009 at 2:19 PM
yes, there is something you are missing. i said you need 6 relays, not five. you need this setup plus 1 more relay to change the positive output to negative polarity (see relay section again if you dont know how that is done)......or......just get an electronic latching relay.
Posted By: themodifier
Date Posted: March 03, 2009 at 2:57 PM
I am trying not to sound ungrateful. I looked at the relay page, and I do not see a diagram with 6 relays, nor do I see instructions on how to add a 6th relay to the latching relay set-up. Could you please direct me to this diagram(or copy and paste). If not,maybe you could direct me to the instructions on how to add this additional relay. Sorry to be a pain.
Posted By: ckeeler
Date Posted: March 03, 2009 at 3:23 PM
no biggie. 
Posted By: themodifier
Date Posted: March 03, 2009 at 10:19 PM
Very Much Appreciated!!!!I'll give it a try once I have the rest of my wiring harness completed. I'm still waiting for some of the components to arrive. I've noticed in several forums that many have given up on trying to use as much as possible of the factory set-up, and bypass the BCM. They usually scrap the factory set-up, or go to the dealership to have their BCM's "flashed", because the vehicle didn't come equipped with the option. The dealerships usually charge $90 on average. I'll report back with results, and pic's so that this can be of some assistance to others in the future.
Posted By: theviperman
Date Posted: March 31, 2009 at 9:35 AM
Hi - first time poster. Though I have not priced out the components of this diagram completely, my guess is that the relays are $5 a piece, plus at least $6 in wire (should probably use a few different colors) and at least $4 in connectors for the relay pins Total is 40 dollars and a few hours of soldering, etc... You can also go and buy a TR-7 module from PAC - it's a 7-function module that you program for it's first use - function "3" is a latching function, all done electronically. I have been using the TR-7 module in a kit I sell online for over 3 years now. My reason for visiting this site is that the TR-7 has risen to about $33, shipped (purchased through The Better Source in Chicago) and I'm trying to find a new way to do this cheaper. Search for "PAC TR-7" in google - you'll find it easily. MUCH easier to work with than multiple relays. Jeff ------------- Don't mind me...
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