rewiring reverse lights?

Printed From: the12volt.com
Forum Name: Lights, Neon, LEDs, HIDs
Forum Discription: Under Car Lighting, Strobe Lights, Fog Lights, Headlights, HIDs, DRL, Tail Lights, Brake Lights, Dashboard Lights, WigWag, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=113089
Printed Date: May 13, 2025 at 5:04 AM

Topic: rewiring reverse lights?

Posted By: orangesuburban
Subject: rewiring reverse lights?
Date Posted: April 12, 2009 at 3:26 PM

hey guys, i am having my taillights painted and i was wanting to rewire them as a result. due to my tint and then the tail lights being painted the reverse lights will be all but pointless so, i was wanting to make them more functional.

this is on a 2008 Scion xD

there are 3 bulbs in the tail lights

top bulb is a 7443 bulb is used for the night running lights and also the brake lights
middle bulb is a 992 (7440A) for the turn signal
and lowest bulb is a 921 for the reverse light

i want to replace the white bulb with a red bulb and rewire the lowest location to function in the same manner as the top location. (running and brake)

i know to get one function i could just cut the wire and tap power at the top bulb, but i dont know what to do to get both functions.

i plan to swap out the white 921 for a red 194 LED (if LED vs bulb has an barring on things)

what are my options!?

thanks guys!

Replies:

Posted By: i am an idiot
Date Posted: April 12, 2009 at 4:01 PM

Is the 7442 a dual element bulb?

Posted By: orangesuburban
Date Posted: April 12, 2009 at 4:26 PM

7442?

if you mean the 7443, yes that one is a dual element. none of the others are however.

Posted By: i am an idiot
Date Posted: April 12, 2009 at 4:54 PM

Yes that was the one I was asking about. It would be very simple if you could change the sockets to accept a dual element lamp. If that is not an option, we can still make it work with the sockets you have. On the socket for the reverse lamp, are both the ground and hot wires accesible? You will have to cut both and using 2 relays, will have to switch between series and parallel wiring. When park lamps are on, the lamps are going to be wired in series. Thus making the bulbs burn at half brightness. When the brakes are depressed, they will be wired in parallel. Full brightness. There is a diagram on this site for switching speakers from series to parallel. I will look at it and see if it needs any modifications to do this.

This is the diagram for the speakers. It will take some modifications to make it do what you are looking for. I have no problem modifying it if you tnink you are going to do it. Let me know if I need to modify it.

Posted By: i am an idiot
Date Posted: April 12, 2009 at 5:16 PM

We may need a third relay if you want this to work during the day. When I drew the diagram, I was thinking you had daytime parking lamps. A different post here. The diagram below will work at night. I will need to modify it for brake lights in the daytime.

posted_image

Posted By: orangesuburban
Date Posted: April 12, 2009 at 8:45 PM

all wires are accessible, please do modify it for my application this is something i will 100% be doing.

thank you!

Posted By: orangesuburban
Date Posted: April 12, 2009 at 8:47 PM

thank you... the only change would be the lower pos connection needs to go to an ACC power wire rather then the park light connection, no?

Posted By: i am an idiot
Date Posted: April 12, 2009 at 8:58 PM

An accessory wire will be fine, the only problem with that would be the running lights would be on anytime the key is on. I was thinking more in the lines of a relay that would supply voltage from either the park lights or when the brake is depressed, Nevermind I will draw a picture.

Posted By: i am an idiot
Date Posted: April 12, 2009 at 9:14 PM

posted_image

Posted By: i am an idiot
Date Posted: April 12, 2009 at 9:16 PM

When parking lights are on, the lamps will get voltage from that wire. When the brake is depressed, power will come from that source. In the daytime, only the brake lights will illuminate.

Posted By: orangesuburban
Date Posted: April 12, 2009 at 9:19 PM

ok so, you drew the 3rd relay upside down just to confuse me?

left lamp pin 86 right lamp pin 85 and 3rd relay pin 85&87 to brake light wire
(LL) 30 to (RL) 30 to (3rd) 30 to parking light wire

just want to make sure i got the third relay correct.

Posted By: orangesuburban
Date Posted: April 13, 2009 at 5:27 PM

got it all wired up. now just got to wait for the lights to get back from paint (left the bulbs in the housings so i didnt have to worry about overspray inside) only 7 connections away! thanks!!!

Posted By: i am an idiot
Date Posted: April 13, 2009 at 6:43 PM

Stop Where do you see the left lamp or the right lamp connected to 85 or 86.

Yes I drew it upside down. Not to confuse you but to make it easier to understand.