electrical/wireing assistance

i'm going to re-do the lights on the back of my rig. the lights that i plan to use have 2 bulbs inside each housing, each with its own positive lead (and one common ground). i want to run a three way switch in an on-off-auto fashion.

when the switch is in the "auto" mode, i want only one of the bulbs in each light to activate through a relay tied to the OEM reverse lights. when the switch is in the "on" mode i want both bulbs in each light to activate through a relay tied to a continuous power source.

the following is a diagram that i think will work (it's rather obvious that i'm not an electrical engineer).



the purple circles with arrows are supposed to be diodes.

my first question is, will this work?
my second question is, do i need another diode where the big blue arrow is?
my third question is, what kind/type/size of diodes do i need?

TIA.

out of all of the geuinesses here, no one knows about wireing with diodes?

If you use a double pole double throw switch you don't need any diodes or relays. One pole switches each of the lights, with each light hooked to the center of the switch. One light is switched between the backup signal and a 12V source. The other light switches between 12V and nothing. In the diagram below the 0 are poles of the switch. Hope this helps,
Dave

light +--------|
12 V-------0 0 0--------------backup signal
light +--------|
12 V-------0 0 0

It's entirely possible I'm missing somehting, but what are you trying to de, exactly? Just wondering...

5-90

5-90 said:

It's entirely possible I'm missing somehting, but what are you trying to de, exactly? Just wondering...

5-90

Click to expand...

i'm putting two lights on the rear of my jeep to serve as auxiliary back-up lights and rear work lights.

the lights that i want to use have two bulbs enclosed within a single housing. in that single housing, each bulb has its own positive lead, and the two bulbs share a common ground (making three wires that exit the rear of the housing).

i want to use a three-way switch (no momentary, just on-off-on) so that i can have the following three options for the lights:

• lights off
• lights automatically on, triggered by the factory reverse lights ("auto" mode)
• lights on ("on" mode)

when the switch is in the "auto" mode, i only want one of the bulbs in each of the light housings to come on. when the switch is in the "on" mode i want both bulbs in each of the light housings to come on.

OK, a little more info here. What wattages of bulbs are you using, and are they wired separately within the housing (apart from the common ground?) I'm thinking you're on the right track, but you're overdesigned a bit. You need:

DPDT switch (ON-OFF-ON, they don't really come any other way.)
(1) relay for "auto-ON" ckt
(1) relay for "full-ON" ckt
Fuzes and wiring to fit. Beyond that, you probably don't even need the diodes, but I'll know more once I see what you're doing. The simplest way is usually the easiest...

5-90

Have the normal backup lights activate a relay controlled by a switch in the cab. Turn the switch on to allow the relay to work. Relay powers accessory lights. If you want the lights on even when not in reverse add additional wiring for that purpose.

OK - I've burned some skull sweat and here's how I'd do it...

You will need:
(1) SPDT switch (cover optional)
(2) Bosch/Hella relays, SPDT or SPST
(3) Sockets for Bosch/Hella relays, available as aftermarket part from Borg/Warner
(1) Power distribution terminal (You can get these for a few bucks from Gall's Public Safety Supply, and they're worth having. You'll probably add more stuff back there anyhow... I install mine inside the left rear fenderwell, behind the trim)
8 or 6 gage wire to reach to the back of the XJ.
(1) "Side Tap" wiring connector for reverse lights
Appropriate wiring for rear auxiliary lighting

Wire the switch common terminal to a suitable ground, it will be the return path for the relay coils. One relay will have the coil actuated by the +12V to the reverse lighting (IIRC, they are "hot switched" so this will work) and BOTH to constant +12V. Neither will work until the ground path is compleat. I would put the relays and power post inside the fenderwell, and any additional fuzes fit well in the fuze block I have installed on the centre console right next to my right knee. (Inverter, aux power points, and some lighting.)

Wire one side of each relay's "switched" section to +12V, and pass that to the lights you want to control. Wire the other side of the lights to ground.

I know the wiring plan sounds funky, but here's the idea...

When the switch is in the "reverse actuated" position, only one relay will have a ground AND power path, and only half of your lights should come up. When the switch is in the "override" position, then both relays are energised and will work. Make sense?

The idea here is to use as few components as possible, and to save digging around for high-current relays (which ususally ain't cheap!) Also, fewer parts means lower potential for failure, which is also a very good thing!

Email, PM, or respond if you have any questions...

5-90

Oh - Gall's - www.galls.com. And, a decent source for Bosch/Hella relays and sockets in bulk is Allied Electronics - www.alliedelec.com

5-90

thank you all so much for your help. i think that we're almost there.

from my origional diagram i've simplified a bit and gotten things down to one diode.


the problem seems to me to be with the "reverse" circut (in blue). the bulbs that are connected to the reverse circut will also have to be connected to the "work" circut (in red). I COULD BE TOTALLY WRONG, but i can't see how, without a diode, that when the "reverse" circut was activated there wouldn't be a bleed-over of power through the shared wiring of the common bulb.

if i am wrong, please let me know so that i can learn from my mistakes.

the bulbs are 55w each (X4). i am planning on using the hella relays.

If you use a double pole double throw switch as I mentioned in my previous post you don't need a diode. And if you have a heavy enough switch you don't need relays. You mentioned 55W is that per light or for two combined ? Even if the lights are 55W each the lights take 4.58 amps and there are plenty of switches available that can handle the load. If I could post an image I would show how to change your wiring diagram to make it work without the diode. Send me a PM with an email address and I'll send you a wiring diagram.
Dave

DaveB -- you've got PM