Originally Posted by TwelveVolt
Could someone explain the circumstances under which one would choose to install additional brake bulbs? Intuitively, it seems like a lot more effort than installing a couple of diodes in the existing brake light wire.
You asked for an explanation. In reality, it's a simple decision to go either way. The amount of Physical work, is actually very close. For 99.99% of the vehicles out there, the amount of wire you use/run to get to the back of the toad and do the required work, is identical. But from that point, the similarities change. Many guys are deathly afraid of tying into the factory wiring, for various reasons. Either they've screwed things up in the past, are not sure of their capabilities, had a friend who had a friend who...... goofed things up and had issues, who knows but, they just don't like tying into the factory wiring.
Up until very lately, as in 2012 and newer, tying into just about any toads lighting system is very easy and, in terms of the amount of physical work, doesn't get any easier. There is one exception and, I'll go into that later.
But, the plan is simple. You have wires, factory wiring that is, not the ones you're installing, leading from the front of the vehicle to the toads tail light assemblies. In simplicity, it can be four wires or three wires to each light. On a four wire system you can have:
1. Turn signal light wire (usually for an AMBER lens)
2. Brake light wire
3. Running/tail light/marker lights
On a three wire system the only difference is the elimination of the turn signal wire because the turn signal and brake light wire, is the same wire.
Ok, now you've got the basics. So, when tying into or, splicing, or what ever term you want to use, is done, the way I do it is, find the wire that you want to tie into, i.e. the left turn/brake light wire. I then strip a small amount, usually about 3/8" of an inch ( I don't cut that wire, just strip some of the insulation from it) very close (within a couple of inches) of where it enters the socket plug. I then wrap the appropriate wire that I installed, around that newly stripped section. I then solder it nicely. I then tape it very securely. DONE.
Now, I do the same exact process to the running light/tail light wire. DONE.
Now, I then extend the right turn wire across the underside of the toad, securing it along the way, and up into the backside cavity of the right tail light. Then, I find the RT turn/brake light wire and, do the same exact process. DONE.
Now, the main reason for the installation of DIODES and, where they're installed is, they prevent the signal from the motor home from traveling down stream into the rest of the toads lighting system which, in many cases, can cause the issues some have had.
So, I don't buy the expensive "Diode" packs from Camping World and other RV supplies outlets. I purchase a four pack, from Radio Shack for about $2.98. A diode is a diode, no matter how fancy you package it. So, this is where I DO cut the wires. Just down stream from the "T" joint I've done on both the right and left turn/brake wires, I cut them and install the diodes. I then tape everything very securely and, DONE.
Now, the system is done. And, to me, when towing the toad, and someone is following me and I present signaling from the motor home, the toad presents the same exact picture (in lighting) as it does when someone is driving that toad. To me, it's more natural and normal to the public following it.
Now, as for installing separate sockets and bulbs, as stated, the amount of wire needed to get to the same place of work, is identical. So, here's what most guys do, they select a spot, on the back of the tail light housing, where they can drill a large hole to accommodate the new socket. Now, that socket and bulb, must not come in contact with the factory bulb. Now, once the socket and bulb is installed, the wiring is academic. For obvious reasons, there is no need for any diodes in any portion of that style of installation.
And for the most part, there are no separate "un used" sections of tail light housing, that are completely partitioned off, for the installation of an aftermarket socket and bulb, with only very, very few exceptions.
Now, here's where I find at least one issue with that style of installation.
If you've installed your own bulb, right next to the factory bulb and, you have an "AUXILIARY BRAKING SYSTEM" installed in the toad, and, that braking system activates the toads brake lights, even when the key is off, and you put your turn signal on in the motor home, you now have a blinking light (your newly installed one) right next to a "BRAKE LIGHT" being activated by the toads brake arm. So, you have two bulbs, displaying two different signals, within an inch or so of each other and, for the most part in an "un partitioned tail light housing".
If you have, as one poster mentioned, a separate, unused section of tail light housing, that IS partitioned off, then the matter is not so much of a problem.
So, there, all be it long, is at least my explanation of why I do what I prefer. It's a free planet so, anyone can choose their own method. Now, I mentioned another way of tying into the factory wires. I've never used them but, apparently some have on here. There are newly designed, "PLug and Play" kits you can purchase for tying into the factory wiring. Just how and how well they work, I don't have any experience with them so, I cannot answer that question. I hope this, (long) explanation has helped some. Good luck.
P.S. I forgot to add the reason for it being harder to do my kind of installation on 2012 and newer cars. It seems many of them have gone to what's called the "CAN BUSS" wiring system. It's a totally different kind of wiring system and, goofing around with it can cause multiple issues. At this point, I'm not sure how to get around it, if one still wanted to tie into the factory lights.