Adding more Marker/Clearence lights

Highway Yacht · February 24, 2009, 03:03:53 PM

I want to add a couple more 12v marker/clearance lights to each side of the bus while I've got it stripped and have access to the wiring. Can I just tap into the marker/clearance light wires that are already in place and just up the fuse a few amps to cover the extra lights without any problems? I've heard too many lights on a single wire may cause some lights at the end of the run to be dimmer than the lights at the start of the run but not sure there is any truth to that. Any tips or advice??? Thanks

WEC4104 · February 24, 2009, 03:25:27 PM

To properly answer this question, it would be necessary to know what the wiring circuit looks like.

Keep in mind that the fuse value is selected to protect the wiring and other components from carrying more current than it was intended to. Naturally, there is a little safety factor build in, but up the fuse value and stress it too far and your circuit will become the fuse.

In most wiring configurations, the lights at the end of the run will not become dimmer. If wired in series, it is possible that all lights will become dimmer.

Depending on your wiring config., adding LED type marker lights might be your answer, since they will add less of a load to your existing circuit.

Tim Strommen · February 24, 2009, 03:32:28 PM

First - NEVER up the size of a fuse for a given wire that has been engineered...

The ammount of current that a given diameter of wire can carry is limited. A wire also has its own resistance, which is in itself a load, but when designed correctly, is only a small percentage of the total load. If you have too much current going through a wire, it will get warm as it approaches it's capacity, and this heat causes the resistance (load) of the wire to go up. Keep in mind that energy likes to take the path of least resistance - that term resistance can also have the engineering meaning (thus energy likes to take the path of least "load"). So yes, it's possible that if you add too many lights to a circuit, that some lights will be brighter than others.

The fuse's job is to protect the wire from having so much current go through it that it's self-heating becomes a significant part of the load (remember, the hotter it gets, the more it smokes and it can start an electrical fire).

This is a website that has usefull stuff like wire-size calulators that can help you learn to answer this question yourself. This is a non-comercial site (except for selling CD copies of the site, which I don't recommend since it's available online...) and I'm not affiliated with it in any way.

Check out this page on his site specifically about wire/wire-sizing. Almost all the way at the bottom (just below the wire gauges table), there is a calculator that will let you plug in the wire gauge, current and length, and will tell you "go/no-go" if the wire size is too small.

-Tim

Highway Yacht · February 24, 2009, 03:33:34 PM

Thanks for your advice. I too was thinking LED's might be the route to go. Maybe I can pick up enough to even change out my current marker/clearance lights that are already on the bus and have them all match. That would also decrease the draw even more on the fuse and the wiring. Thanks Again

Jimmy

Lee Bradley · February 24, 2009, 04:17:04 PM

You can add lights but they must work. Same ticket for non-working supplemental as a non-working required.

Highway Yacht · February 25, 2009, 05:29:35 AM

Quote from: Lee Bradley on February 24, 2009, 04:17:04 PM
You can add lights but they must work. Same ticket for non-working supplemental as a non-working required.

Ohhh I do plan on them working. I'm not wanting a Christmas tree by any means but do like the looks of a couple extra lights along the sides instead of just one up front and one in the rear. My plans are to add just 2 more lights along each side.

BG6 · February 25, 2009, 06:18:02 AM

Quote from: jlink on February 25, 2009, 05:29:35 AM
Quote from: Lee Bradley on February 24, 2009, 04:17:04 PM
You can add lights but they must work. Same ticket for non-working supplemental as a non-working required.

Ohhh I do plan on them working. I'm not wanting a Christmas tree by any means but do like the looks of a couple extra lights along the sides instead of just one up front and one in the rear. My plans are to add just 2 more lights along each side.

What Lee is saying is that adding more lights means adding more things which can fail. If a light DOES fail, it doesn't matter if the law required it to be there or it's one that you put on for the look. Thus, adding more lights means adding more reasons for a citation, if you run into a cop who is looking for one.

TomC · February 25, 2009, 07:07:27 AM

When I added clearance lights (4 more to each side) I used the interior overhead lighting circuit. Wiring ran right down either side of the bus so was convenient to use. If you don't have that, I suggest you remove the old style lights and replace all with LED for the low amp draw they are known for. You'll be very pleased at the way they look too. Good luck, TomC

Sean · February 25, 2009, 10:30:00 AM

Switching out your incandescents for LEDs will, essentially, let you add as many lights as you wish on the same circuits. Bear in mind that if you do this with turn signals, you may need a different flasher unit.

If you do decide to make the change, be aware that it is not as simple as plug-and-play. As an example, my Neoplan had combination lights at the top front corners. Due to the curve of the roof there, no LED combination lamp could be used. We ended up using separate clearance and marker lights at those corners.

Also, be aware that the allowable installation angles for photometric compliance are different for LED items than for incandescent. Many LED side markers must be installed on a vertical surface -- if yours are on the curved part of the roof line as ours are, you need to get items that are approved for that angle.

There are lots of rules about exactly where lights can (and can't) be installed, so if you are varying from the manufacturer's original installation locations, make sure you read up on them first.

-Sean
http://ourodyssey.blogspot.com

Highway Yacht · February 25, 2009, 01:10:25 PM

Thanks Guys.. I do really appreciate all the tips and advice from this group. Its so much better having a project looked at from several angles than just mine. Right now the bus is stripped on the inside and I have access to a great deal of the wiring. The bus is not painted yet so I should have no problem in changing out existing lights with LED lights for my straight panels. I do have a couple existing lights on a slight curved panel on the front of the bus so I will have to see if I can find some LED's that will work there. Thanks Again!!!