Hi Gentlemen,

I hope you all had a great start into the new year.

I did quite some research, inside the forum and also on the web, on the turn signal issue I recently discovered. Unfortunately I didn't find a matching thread, so I hope not to bore you too much with another "turn signal" question (there are quite a few here already).

Basic truck setup:
Aftermarket turn signal switch from speedway, type 910-62860
https://www.speedwaymotors.com/Speed...ch,343533.html
Standard Light bulbs, no LED
2 to 3 wire adapter box for the trailer, Reese 118158
https://www.rvautoparts.com/118158-T...r_p_11380.html

So far turn signals and brake light works as expected when using turn signal, with or without brake, also with trailer connected.

As I have to go to inspection soon I checked the whole lighting system of the truck to avoid trouble.
So I switched on the hazard, truck only - no trailer, and it works fine until I use the break. Then all 4 bulbs turn on solid and the flasher stops.
Connecting the trailer and turning on the Hazard shows that instead of the turn signal bulbs the brake lights on the trailer start flashing. When using the brake all 6 bulbs (truck and trailer brake lights) go solid, no more flashing.

To rule out the 2 to 3 wire box or the trailer wiring I disconnected the conversion box but the issue still remains with only the truck lights.

I found a schematic on the web which should match the principle of function and according to this and some thinking about the error my only conclsuion is that inside the turn signal switch the power connection of the brake light switch doesn't get interrupted when turning on the Hazard (red arrow).


Maybe you have some other ideas or suggestions what could cause the problem?

Anyone ever had taken such a turn signal switch apart? Can it be "fixed" or does it need to be replaced?

Thanks upfront for your help!

Greetings from Germany
Uwe

 

Welcome Mr Newbie. I will try to pull out my wiring diagram for my flashers. I also did an aftermarket turn signal set up. As I recall, there are 7 wires My unit had a built in flasher, I believe.

 

If I understand your issue, when using the emergency flashers, and only when using the emergency flashers, using the brakes makes all of the signal/brake lights come on and stay on at once. When you take your foot off the brakes everything goes back to flashing.

I think that is normal on most older vehicles with “simple” signal/emergency flashers.

Using the emergency flashers bypasses the normal turn signal pathways and ties all four corners into a single circuit. Using the brakes is bypassing the flasher because brake lights are more important than the emergency flashers.

Your trailer “box” is seeing right and left signals together and interpreting it as brakes. Again, that is normal.

I remember as a kid hitting the brakes with the emergency flashers on would make both the arrow indicators on the dash come on and stay on. For some reason I thought that was cool.

 

Hi.

thanks for the responses so far. While searching for answers I saw some schematics that would make sense to what is happening, as you describe, EffieTrucker.

But the car went through inspection in 2017 when it got first registered in Germany. If the hazard would have stopped when using the brake or the wrong lights would have blinked at the trailer it wouldn't have passed inspection. Also inspection in 2019 was no problem, so I have to assume that the wiring and function as it was up until whatever happened must have been OK. Since I got the truck last year I didn't touch any turn signal wiring, that's why I suspect the switch to be the one part that somehow is failing.

BR
Uwe

 

Here's little simpler diagram I did years ago that shows how the circuitry works in action. Also, double check all grounding. Grounds can get dirty over time and do strange things to lights.

 

Thanks for the diagram. I also looked at that one but it doesn't contain the hazard function, that's why I posted the other one.

Well, I found the problem. I took the turn signal swicht apart and saw that the function is as EffieTrucker describes, it seems to be normal for older, simple setups. The switch has no function of interrupting the brake light signal when Hazard is on.

I just wonder why none of the inspectors tripped over that .

Anyway I try to get it up and running as supposed.

Does anyone know of an aftermarket turn signal switch which interrupts the brake switch signal when Hazard is on?

Thanks!
BR
Uwe

 

I remember when 4 way flashers first came out (1968??) they worked like that. Even the indicators on the dash stayed lit when the brake lights were on.

 

I will check with an inspector about his opinion.
Anyway I'm going to rewire the trailer connection, taking out the 2 to 3 wire box, so at least when hazard is on the turn signal bulbs will work correctly.

BR
Uwe

 

Finished the wiring, disconnected the 2 / 3 wire box.
- Run an extra wire from the brake light switch to the trailer connector, needed to add some diods to block reverse power from the turn signal switch.
- Connected the trailer turn signal to the front turn signal of the truck.
All fine now, except the blinking stops at hazard when using the brake but that shouldn't be an issue (depends on the guy inspecting). Mostly they don't test this (that's what I was told).

 

That is the way most older vehicles worked and it's unlikely anyone would ever check that combination .