Aight, you guys said to use a relay when hooking this up. I was wondering what kind of relay should i use? I was thinking about just hooking up the power wire from the fog lights to that of the bed light..and then just grouding the light. Is there somehting else I need to do or will this be sufficient?

 

JasonG,

Generally you should always design electrical systems with components that have about twice the rating or "capacity" as you need. Because of this the factory wiring likely work depending on the wattage bulbs you are using but you are reducing the margin of safety.

That said...
whenever you add additional items to the factory wiring you should supply the additional current through a relay directly to the battery or some other high current source.

(The factory wiring will easily activate the relay with no reduction in this safety margin.)

MOST generic automotive relay contacts are rated at 20 - 30 amps and require only about 200 ma to operate.

In the future, if you want to determine what "size" relay you need, divide the wattage of the bulb by 12 volts. That will give you the current it will draw. Multiply that by the number of bulbs for the total current required.

That would be about 10 amps for two 55w bulbs. So a 20 amp relay is perfect and will give you that margin of safety.

P.S. Throw a 15 amp fuse in line near the battery or current source and you'll be just fine!

Good Luck... XLT_D

 

aight...so basically when i wire up my lights I need to have a relay connecting everything? Am I correct on that

 

JasonG,

Yes, that is the best way.

A relay allows the control of high current (20-30 amps) with a small current (200 ma.). Sort of like a "remote controlled" switch.


It has been explained here before but let me try it again...

the relay's switch contacts go between the battery and the new bulbs you are adding. This would be pin numbers 30 & 87 on most relays. (Place the proper value fuse for the load at the battery connection.)

The relay's activator terminals (pins 85 & 86) go between the lighting circuit you are using to control the new lamps and ground. A fuse is not required in this circuit since the factory wiring is adequate for protection.

Since these generic relays and bulbs are not polarized, it does'nt matter which contacts go to +12 or ground.

Now, when the factory circuit is turned on, the relay contacts close and switch +12v to your newly added lamps.

Good Luck... XLT_D

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Well I'm gonna try and put the lights on this afternoon, I'll let you know how the install goes and where I mounted them.

 

So now we have on group of people doing a complete rewire from the battery back with a relay etc. then the others just tapping into the bed lights with a simple splice. Which is right, better, simplier, safer, easier etc? I am confused. Can the stock wiring and fuse handle and additional one or two 25 watt bulbs per side? Help. Thanks

 

J Evans,

In my first reply to JasonG, I stated the "rule of thumb" (sort of speak) that you should design wiring, etc. for about twice the expected need. This creates a safety margin and prevents componenets from failing due to excessive heat(ing).

I also mentioned the size (wattage) of the bulb mattered. Adding two 25w lamps to the circuit is an increase of about 3.8 amps.

ASSUMING the auto makers use this "rule of thumb", then the bedlamp circuit should be able to "absorb" the addition of two 25 watt bulbs (especially since they are only on for 30 sec. or so at a time).

BUT this additional current does reduce the safety margin.

Always use a relay (~$5). You don't have to go to the battery. If you are wiring from the left side, you can get +12v at the engine compartment fuse box too. Place your additional fuse close to the source to protect as much of the new circuit as possible.

Right, Wrong, Better, Safer, Simpler? Research the topic and decide whats right for you.

Good Luck... XLT_D

 

XLT_D you said it right.

Although taping into the existing wiring is simpler, it does reduce the safety zone for the factory wiring. A relay is better, just little more time consuming.

I've had my lights on for about 10 months and have had no problems. But I may change it out to a relay circuit one of these days, just to make me feel good.

All in all, this is a great mod. Do it and enjoy!

 

Well I installed my lights last night and it took me all of about 30 minutes. I wired them straight into the wiring and will probably put a relay on this afternoon but for the time being they work fine. I just used some cheap fog lights and aimed them up so they reflected off the underbody of the truck.

 

Jason, those look good. You said you used cheap fog lights. What price range were they in? Last time I looked at Shucks they started at about 40 - $45.

Sorry but I want to make sure I get this correct. You bring power in from the battery or fuse box, use an inline fuse, running this power through the relay and onto the lights. What about running this line on the drivers side then crossing under the truck to the passengers side? Not a good idea? Too much chance to catch on something or what are your thoughts? You then run a wire or line from the bed light wire to the relay to trip the relay switch when the bed light comes on. Is this correct? How big is the relay and where can you place it? Then inline fuse should be as close to the power source as possible, should it be right at the fuse box? What is the easiest wasy to tap into the fuse box? What size wire should I use? Is there a problem if I use oversized wire? Sorry but I have done very little automobile wiring. Thank for all of your help. All of you.

 

Gentlemen,

JasonG...
Yours look great! Just the right light pattern.
Those "cheap" lights might actualy have 37.5 - 55 watt bulbs in them. If so the additional current is between ~6.3 and 9.2 amps.

J Evans...
No problem to explain further...

To add a relay (takes more time as deep6blue said):
attach fuse to + terminal of battery,
runwire from fuse to one of the relays "contact" pins (#30 or 87), run wire from remaining contact pin to one side of EACH of the new lamps (otherwise each lamp would only get ~+6v),
run a wire from remaining side of each new lamp to ground.

That completes the current supply wiring.


Now run a wire from the +12v switched side of the bedlamp circuit to one of the relay's "coil" pins (#85 or 86), and the remaing pin to ground.
(Its important to tap into the switched side of the circuit rather than the ground side to avoid the additional current to activate the relay from being fed through the lamps.)

That completes the activation wiring. The new lamps will now illuminate with the bedlamps.

Misc:
Use 14-16ga. wire, no problem for bigger size (smaller ga. #).
Mount relay away from water and extreme heat (in cab is good),
Taping into fuse box is OK but not recommended for self proclaimed "newbie's", can be difficult.
For two 55w lamps- Relay shoud be contact rated for 20-30 amps(most automotive types are),
In-line fuse should be 20 amps,
I would crossover under hood rather than underneath truck especially if you go off-road.

It's all about safety (margin)!

Good Luck... XLT_D

.

 

Thanks for the info but as always I have more questions. Don't want to bite off more than I can chew. I have a 2000 F-150 if I connect at the battery is it easy to find a place to get the wire into the cab? How big is the relay and where in the cab might it fit? How hard would it be to cross over in the cab? as there are holes in the door sills to get under the truck. How do you tell the "switched" side of the bed lamp? Thanks again. I'm sure I'll come up with more. Have a great day.

 

J Evans,

I have not done this mod. but have added additional back-up lamps using the exact method described.Therefore I did not need to bring any wires inside and the relay is wrapped in elec. tape and stashed high behind the tail lamps.

I believe you'll find a grommet above the gas pedal cable that you can use for routing your +12 into the cab.

The generic automotive type relays are about 1 cubic inch plus a mouting tab and 4 - 5 electrical connectors.

Cross over in the cab is definately possible and would easily facilitate mounting the relay in the cab.

I did some research and found that the dome lamp and bedlamps are on the same circuit. The switched +12v wire is 'black with lightblue stripe' and will be found in the passenger side kick panel.

If you pierce the insulation with a pin and connect it to a DVM referenced to ground you should measure ~12v with the dome lamp on.

XLT_D

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What about installing a 18" neon tube behind the side steps? Would you use the same amount of power and amps? Would this be easy and tap into the same wires? I just think neon would add a softer glow and give a wider spread of light. What do you think?

 

I had thoughts of using that rope lighting to provide like you say a softer but more even light. I don't know this gets more complex as the posts grow. I am insterested in seeing what everyone says about these two types of lights.