I have a 52 Chevy truck that has wiring for separate brake and turn signals but only stop lights that do not have dual filament bulbs or sockets. I bought a 3 to 2 converter for trailer wiring. It seems simple but maybe I am missing something? There are three input wires Red = Stop, Yellow = Left, and Green = Right. The device has only two output wires (yellow and green). When I supply power to the red input wire, I am not getting power coming out on the yellow and green. I also get nothing from supplying power to the yellow input or green input. I assumed the device was defective and returned it for another one. That one does the exact same thing. I have a good ground and the stop lights work when the brake light wire is connected to both stop lights. I am not using LED bulbs, just regular incandescent bulbs. Any ideas on what I might be doing wrong or recommendation on a good 3 to 2 converter?
I am guessing your 12 v neg ground. when I used an old 3 wire turn switch & used a trailer converter I had to put more load on it to get the signals to blink I had 1157 in the back & 89 bulbs in the front I added 1156 bulbs up in the dash to make it work
Thanks Tim. The flasher on this truck works with just the stop lights and LED front turn signals. They make special flashers for LED lights that do not require much of a load to flash. In my case, I am not getting any output at all. Turn signals or brake lights get no output power. I did only try it with two small incandescent bulbs on each side for brakes. That is four bulbs, which I am assuming is enough load. The device does say it does not work with LED bulbs, which means it must require some sort of load. I may try a heavy load to see if that creates a closed circuit.
Some of these converters are "powered", meaning they probably have relays in them, and some are non-powered. This one only has the three inputs and two outputs (no ground). The parking lights do not go through the converter, since there is no change to that circuit for parking lights. I am kind of committed to the look of the original style tail lights. I already adapted them to have a new LED parking light (separate circuit). I will try a heavier load to see if that helps. You are ambitious, making your own with relays and diodes. I bet those work more reliably than these cheap little black boxes.
No need to bring in the parking light circuit and I am trying to avoid having to run power to the box, since some are powered and some are not powered. The non-powered are supposed to work off the input power that comes in either via the Right, Left, or Brake light wires.
I am still struggling with this converter. CURT is the manufacturer and they say if more than one doesn't work then it is not their problem and I should take the car to a mechanic. 1. I am the mechanic. 2. these things aren't working on the bench with simple 12V power supplied to Red brake power input and 1157 bulbs on the yellow and green. Does anyone have any ideas of how I can test this to identify whether the device is bad or something I haven't thought of yet could be wrong?
Ok, here goes! I am an engineer and work for a Curt competitor. Here is one of your problems, the brake input must have at least one operating (brake signal bulb) connected with the red input wire. If you are just connected to the brake switch there is no return for the converter to operate. The 3 wires (red, green, and yellow) need bulbs connected to each, with each bulb socket being grounded. It should work after doing this. If you can't have bulbs connected to the 3 wires, then get a converter that is LED compatible, as these types don't rely on bulbs for the returns. They have resistors that take care of the returns.
That is very helpful! I am not very knowledgeable about electrical but I do have ohm meters and a bunch of various resisters. I will try to measure the resistance of an 1157 (turn signal side filament) bulb and add a similar resistance up stream on each input wire. Thanks!
In the past I found that you need light bulbs on the 3 wire side of the convertor, just like it would have when being used for it's original purpose. Lights on the truck/car side and lights on the trailer side. The internal circuitry of the convertor "grounds" out thru the opposite side; as an example during left turn signal input on the yellow wire the convertors internal circuitry "grounds" out thru the green input wire and needs a bulb on that side to complete the ground. The bulb on the input side can either be front signal lights or dash indicator lights. The "ground" current going thru these bulbs isn't enough the light them; just enough for the convertor to work. I don't see how resistors would accomplish the same. I don't remember the brand of convertor we used; it only needed to have bulbs on the left and right input wires; but you may find you need a bulb on the brake input also if you have the one that d2willys described.
This is also very helpful. Thanks. Your explanation of grounding out through the input wires makes a little sense to me, in that this device is intended to address converting the car to a trailer. My thoughts on the resisters is that a light bulb has a certain amount of resistance and completes the circuit. If I match that resistance with a resister instead of a light bulb, the device should not know the difference and I won't have an extraneous source of light to try to hide. The resisters would go from the input wire to ground, not inline. That would mimic a light bulb electronically. Just a thought.
The 1157 automotive light bulb is commonly used in cars for both low and high beam headlights. It features a BA15D double-contact bayonet base and has two filaments located at the bottom of the lamp. These filaments are made of tungsten, a strong metal, and are surrounded by a glass envelope filled with argon gas. When the bulb is turned on, electricity flows through the filament, causing it to heat up and glow, producing light. The argon gas protects the filament from oxygen, preventing it from burning out quickly. Here are the key specifications for the 1157 bulb: Power: 26.8 watts Voltage: 12 volts Dimensions: 45 mm x 21 mm x 21 mm Light Output: 402 lumens Color Temperature: 6500 Kelvin Interestingly, this bulb can be used for various purposes, including: High beam or low beam headlights Fog lights Turn signal lights Brake lights Backup lights Additionally, the 1157 bulb is a good choice for off-road driving due to its durability and ability to withstand harsh conditions1. Now, let’s calculate the resistance of the 1157 bulb. We know that its power is 26.8 watts and the voltage is 12 volts. Using the formula: [ R = \frac{{V^2}}{{P}} ] where: (R) represents resistance, (V) represents voltage (12 volts), and (P) represents power (26.8 watts), we can calculate the resistance: [ R = \frac{{12^2}}{{26.8}} = 144 , \Omega ] Therefore, the resistance of the 1157 bulb is approximately 144 ohms2. Keep in mind that this value may vary slightly depending on the specific bulb and its manufacturing details.
I figured it out. (feeling a little stupid) The truck came to me half assembled with a bunch of wires hanging over the rear axle. I used a test light to find that I had right turn, left turn, brake, and parking lights all on separate wires. I do have LED bulbs on the front turn signal lights. I tried a bunch of things and the brake lights stopped work all together. Further investigation discovered a terrible connection at the switch that was apparently enough to light my test light previously, but not enough to light the rear lights (double bulbs on each side). I fixed the connection up front and found out that the truck already does its own conversion to send power to both on brake and either on turn. That was not working at first because of the bad connection. I took the converter out and have stop and turn signals working as they should. I do appreciate the information people provided. This site is terrific because of the depth of knowledge and your willingness to share.
I think your calculations are incorrect. Let's take the 144ohms and see what you get with 12v. 12/144=.0833 or 83ma. 12x.0833=.999 watts. Quite wrong. Now let's do this correctly. 26.8/12 = 2.23 amps. 12/2.23 = 5.38 ohms. The resistor wattage is the same or higher than the bulb is.
Actually, you're both off. An 1157 lamp will measure 'cold' at about 2.2 ohms. But in operation it's about 6.1 ohms (heat increases resistance). Doing the math, it's 13/2.07 = 6.2 ohms. You'll find various numbers for wattage and voltage (the lamp is seeing more than 12 volts in actual operation), but the commercial 1157 'lamp emulators' that are sold to furnish the correct 'load' for some flashers are all 6.1 ohms. These are all fairly large units (rated for 50 watts) and do put out a lot of heat so care has to be taken about where their mounted to prevent fires. Not particularly cheap either. D2 is correct, you do need that ground path through either the lamp or an 'emulator' to make the convertor work. I see they make a 'powered' unit, I wonder if that isn't the right choice for you.
Good to see that you got it fixed. Nice to see that the PO had already wired it up for turn lights with the separate right side brake/turn wire already in the the truck. We've gone full circle on the turn signals on these trucks since the 40's in that back when they were new and you added turn signals you had to install and extra light on each corner as a turn specific light. Then the brake lights didn't run through the turn signal switch as power went straight from the brake light switch to the stop light bulbs. Then we got turn signal switches with brake lights running through them and didn't have to have separate turn light bulbs. One bulb did it all. 50 something years lather they decided that new cars and trucks needed separate brake and turn bulbs so the soccor moms could see that your were both stopping and turning when they looked up from their phones. Then we back up to our car hauler trailer, trash trailer or boat trailer and damn, we can't get the frigging lights to work without this adapter. That same adapter will let you run that cool oldschool turn signal switch that you bought at the swap meet or cabbaged off that abandoned truck out in the woods and not have to have extra turn bulbs. Pretty simple solution. They have a bunch of them but this is one of the simplest to deal with for a simple hot rod wiring system. You still may have the correct flasher for the light bulbs if you run those bulbs and or the correct flasher for the number of bulbs you run.
The three different lights, one for each function, is actually common on European and Japanese vehicles. I had a 1978 Toyota pickup set up that way, it took a while to figure out a way to hook up trailer lights without adding another wire and bulb. At first, I just added a single brake light to be legal. Later on, was talking to a knowledgeable parts guy who told me about the 3-2 converters. Put one in the wiring before the trailer pigtail and I could pull any trailer that was wired to US standards.
Crazy: I was just showing that the OP's math was wrong. And we do make both powered and non-powered converters for vehicles that have LED tail/brake lights. This is what someone should use to convert 3 to 2 when no loads exist. (The returns are through resistors to ground in the converters).
The Jalopy Journal
