New 4-wire trailer connection/converter, how is it supposed to work?

[Jerry_NJ]

Briefly, I installed a 2" tow receiver and trailer light converter on my 2005 Chevy Colorado when it was new (love the plug arrangement, no splicing required, plug-and-play). This package worked fine for almost 10 years, but I say this without any careful check on how it worked. Then this year after driving the truck for almost a year without any trailer connected my left turn signal started to malfunction, and there was a clear screw-up/mixing between the turn/running/brake lights. The Chevy has separate wires/bulbs for turn signal, no sharing of turn and brake fulfillment. I disconnected the trailer light converter and reconnected the truck's factory connections - that fixed the problem.

Next I purchased a CURT converter and installed it. First I used the LED test plug and found correct operation: running light, left turn, and right turn, and brake being both left and right turn. Then I connected to my boat trailer and it seemed to work fine, except, I noticed a slight changing in intensity of the running lights when the turn signal (and emergency) was flashing. As I didn't have a helper don't know what happens when I have a turn signal on and put on the brakes, I suspect the trailer simply displays braking, no turn. There could be enough "logic" in the CURT to parse the turn and use just the other brake light to indicate braking. In any case I see a small cross feed between the flashing and the running lights... is this a "live with it" or get a 5 wire trailer light package - dedicated/separate bulbs for turn and brake? I am not deeply concerned about the operation I see, but if I have a malfunction in my new CURT, I'd want to exchange it while I can do under warranty.

I have not thrown away my old converter, so I have "spare" plugs and wiring to directly connect a 5 wire (no converter needed) to the trailer... and of curse would have to change to separate the turn/brake bulbs.

 

[bruceb58]

When your brakes are off and turn signal on, the lights on the trailer will flash at the same time as the turn signal on the car. If you have the brakes applied, the light on the trailer will flash but be off while the vehicle one is on.

If you see a cross feed, that is likely a bad ground between your trailer and your vehicle.

 

[Saline Marina]

I believe its simple relay logic used, my guess here is that the flasher/turn takes priority on an individual rear lamp over the steady/brake signal. Reason is if you were stopped at a stop light, with foot on the brakes and had the vehicle control stalk set to right turn, you'd traditionally (meaning old school wiring) have left rear = solid and right rear = flashing to signal the intent to the drivers behind of both brake and turn. Having brake lights take priority would mean that drivers behind would be uninformed about the intent of your direction when you were braking.

A relay is just a simple, reliable, cheaply manufactured device which is capable of doing this function, one relay used for each side. I would guess these are integrated into a "module" that Curt sells.

I don't believe that the Curt module based on a relay could confound the vehicle lighting as you describe as even if the module relay got stuck, the pole piece can't touch both sets of contacts at once, it would be in one state or the other or none if stuck in between.

 

[BaileysBoat]

Running lights changing intensity could just be ground resistance or normal voltage drop with the lights activated. You are getting ahead of yourself if you don't confirm what is actually happening at the trailer.

 

[bruceb58]

I believe its simple relay logic used,

Not likely. Easy to make this solid state for WAY cheaper than a relay. Not to mention you need at least 3 or 4 relays to make this work.

Its just an XOR function and a drive transistor for each side.

 

[Jerry_NJ]

Interesting, relays in this day and age of electronics? The CURT and the predecessor look the same with the newer CURT having a smaller encapsulated "box" about 3/4" thick and maybe 2" by 4". Yes, miniature relay(s) could fit in such a package but I'd expect power transistors or something more modern and long lived.

Not an argument, just noting my interest in the idea of using relays.. they have the benefit of "infinite" isolation between the driving signal and the switched power (lights). This cold mean a high resistance relay could be driven in parallel with the vehicle rear lights - then what? The one that drives the trailer LH Bright Lamp flash contacts could be in series with another set of contacts that power for brake. Hum, if using make/brake contacts with B for Brake and F for Flash we cold see a bright bulb being driven by BF' + B'F So, if the Brake is OFF (B', ie. B-not, equals 1) and the bulb sees the flashing F and the trailer and vehicle flash in syncro, but if the Brake is ON B = 1, the trailer sees F', i.e., the trailer light is opposite the vehicle flash, 180 degrees off. Seems this confirms and connects both inputs from Bruce and Saline. As for getting ahead of my own actions, that's why I come here: get put back on track.

I reused the old ground by splicing the new CURT ground wire to the old converter ground, a 10 year old ground looking at the pavement. Could be a poor ground for the cross feed. The relays should have an infinite isolation between contact functions. I didn't even try the LED test plug to see what happens when I hit the brake with a turn signal on. This I can do without a helper. I have some problems finding a helper to step on the brake while I stand behind my trailer....yes I should be able to see from the driver seat when it is dark..at the time of testing I was parked in front of my garage and the motion sensor lighs were on masking what the trailer lighs were doing when observed from the drive seat, the only place I can put on the brakes.

 

[Jerry_NJ]

Exactly my first thought, the BF' + B'F could be transistor logic...but that could also account for some cross leakage and the modulation I see in the running lights.

 

[bruceb58]

Here you go! 2 relays per side for a total of 4.
http://bob_skelly.home.comcast.net/~bob_skelly/TailLights/taillight_mods04.html

 

[smokeonthewater]

cut a piece of wood to put between your seat and brake pedal...... Move the seat forward..... walk to the back of the trailer........



UGH dang engineers...... LOL J/K guys

 

[Jerry_NJ]

I think three relays would do it. Using my already developed notation, and adding FL and FR for Flash Left and Flash Right We are able to use the same B relay to provide two isolated circuits: B'FL + BFL' for left side bright bulb and B'FR + BFR' for the right side bright bulb. I haven't given it enough though to be sure but I think the B relay has to have two transfer contacts (break/make) sets to isolate left from right.

Good idea, I have about every wood working too known to man and made form some picket fence boards (1x6 inch by 6 feet) two replacement arms for a 20+ year old Adirondack chair... I think this just about completes the job of replacing each board in the chair, but I still consider them to be my 20+ year old Bean chairs. Best part, I purchased the fence boards for $1 each from Lowes. Thus, 50 cents each for materials in each new arm...plus some glue and worn out sand paper.