adding turn signals with brake lights

Hopefully that picture is attached correctly!

Just wanted to first say thanks for all the wealth of information here, it is greatly appreciated.

So I have a original 1927 model T roadster with a hemi. I got the whole car wired up and fired up. Only problem was I was using a 2 wire 1157 bulb and socket. I had turn signals and brake lights, but wanted park lights on the dim filament and the turn and brake on the bright.

When I had everything working before, the power for blinkers came out of the fuse block, which has a built in flasher. That went straight to a toggle switch, on off on. From there I ran wires to front and rear for signals and all worked fine.

I went by this diagram here so I could add the turn and brake on the bright filament, park on the dim, and grounded socket to the frame.

Everything works perfect and I followed your schematic exactly. Only thing is when I apply the brakes, I get no turn signals. I let off on the brake and the signals come back on.

What am I doing wrong here? I suspect I might need to change something in the wiring of the relays. I just don't know where to start?

I appreciate the help and hope that wasn't too long winded!

Thank you
Bryan

That's way too complicated.

Use one relay per side for the rear bright filament. Use this diagram as a guide:



Connect 87 to turn sig input PRIOR to the diode.
87a = brake switch input.
30 = output to bright filament.

The capacitor will hold the relay coil on while the turn sig input is flashing, and relay will turn off, reconnecting the bulb to the brake light switch appx 3 seconds after last turn sig flash received.

The diode in the signal input prevents the cap from discharging through the front signal filament to ground.

One diode just seems way too easy! I kept going off other diagrams that people said worked, and none of them did. First one was a 3 relay setup, then the 2 relay. I wonder why those didn't work?

Anyways I'll give this a shot tomorrow, as long as you say the bright filament will be controlled by brake light and turn, as well as the turn signal still working when brakes are depressed.

Excuse my ignorance here, I'm new to the whole relay wiring configurations. But could you explain in lay mans terms what is going on in the diagram where 87 obviously goes to 12v turn signal input, but I'm confused where it comes out of 86 pin.

So 86 pin is connected to 85 with a diode, then out of 85 and grounded.

But where it comes out of 86 towards the +12v turn signal feed, there it the resistor, which then gets grounded, then you have a couple other symbols that bring that run back up to the 12v feed?

I guess I'm just confused on the section that is highlighted in pink, coming out of 86, to a resistor and then grounded, and am not sure how you get that wire run back to the 12v feed. There is a upside down anchor looking symbol and I just don't know this stuff well enough to figure it out. I took a snapshot of the particular section I'm confused by, not knowing the symbol doesn't help. Hopefully this pic will help you understand what I'm trying to explain.

Thanks a million for the help
Bryan

Ok now that I got some sleep, I see it's a cap and resistor, both which have one end to ground. Out of curiosity , why the loop right there? In between the +12 diode and 86?

Not questioning your intelligence, I'm in no place to do that, just hoping it will make a little more sense before I go at it this afternoon

The purple section of the diagram has two 'sections'. The circuit before the diode on the left is the turn signal input. The pulsing turn signal is sent to 87, which when the relay is on, is connected to the filament.

The section after the diode is the control for the relay coil.

The capacitor is like a tiny battery. When the first turn sig pulse comes in, the cap charges up, and holds the relay coil on. Each pulse "recharges" the cap. After the last pulse, the cap discharges through the relay coil, and the 10K resistor to ground, and the relay coil turns off. Returning the filament to brake function. The duration of "on" is appx 3 seconds.

The diode between 85 and 86 is a "anti-spike" diode to deal with the coil spike. It can be eliminated for this application. You don't need it.

I don't know why your other circuits didn't work. I know this one does, because I've used it.

Ok so basically you've got a straight shot from the +12 diode to 86 terminal. You just tie in the cap and resistor and ground the other side of those 2?

Do you happen to have a picture of this that you've done? Trying to figure out the cleanest way to make it look.

Thanks again for all the help

bwatte wrote:

---

Ok so basically you've got a straight shot from the +12 diode to 86 terminal. You just tie in the cap and resistor and ground the other side of those 2?

---

Yes.

bwatte wrote:

---

Do you happen to have a picture of this that you've done? Trying to figure out the cleanest way to make it look.

---

Sorry, I don't have any pics. I put it all in a plastic hobby box, sealed it up with silicon because it was out in the elements in a daily driver, and put it behind the front bumper. I used this circuit to use the front turn signals as DRL's. Like Class-8 Freightliners do.

10K uf capacitors are kind of large and will be fussy to figure out packaging. I'd buy the two caps, and your relays, and find a hobby box that it all fits in. There will only be 6 wires, and I presume this is a fair-weather car only, so no need to weather-proof the installation. Perhaps hot melt glue, or daubs of silicone to secure the components in the box.

You may also leave out the 10K resistor that is next to the capacitor if you wish. The resistance of the relay coil will suffice to make the circuit work.

Ok well I'm on my way with this as we speak, I'll keep the resistor out and just use the cap. I'll follow the diagram to a T and hope for the best.

As far as encasing, it is in the trunk of the car, but not as weatherproof as a modern car by any means.

Maybe I'll just encapsulate it to be on the safe side. That would be done after I run it a bit and make sure all is well.

I am also planning on adding a mini LED to each relay, with correct resistor. I assume it would go from the 30 pin, to resistor, to LED then ground the other end of LED.

I'm working in some real tight quarters so it would be helpful to diagnose a problem with the relays by makeing sure the led is lit or not, since it will be on the output side of relay.

Make sense?

bwatte wrote:

---

.....it is in the trunk of the car, but not as weatherproof as a modern car by any means.....Maybe I'll just encapsulate it to be on the safe side.

---

My thinking is that Hemi-powered street rods aren't generally driven in rain, or even washed. Environmental protection probably isn't necessary.

bwatte wrote:

---

I am also planning on adding a mini LED to each relay, with correct resistor. I assume it would go from the 30 pin, to resistor, to LED then ground the other end of LED. .......so it would be helpful to diagnose a problem with the relays by making sure the led is lit or not, since it will be on the output side of relay.

---

Yes, LED + on 30, resistor, ground will work.

Leave some 'service loop' in the wire harness to the box. Allow yourself slack to pull the box out for access for troubleshooting. Secure the box to the car with double-sided tape so it's easy to get loose if ever needed.

The taillight is on pin 30. So the taillight will tell you the relay state same as your "indicator". So not necessary. Parts left out cost nothing, have no service requirements, and don't need to be installed.

This circuit is reliable. Once assembled with good soldering and fabrication techniques, the installation should out-last the car and its owner without further attention. :grin:

Let us know when it's installed and working.

My taillight is a PITA to get the bulb out to see if it went bad. Every single wiring aspect in this car is like playing twister with the car, tools, hardware etc. then you finally get into position and forget your solder... I made it hard on myself only because I want the wiring clean and hidden. It's the price you pay I guess.

I just figure a simple led indicator could potentially save some time, and a visit to the chiropractor :)

As always, thanks for the help. I'll post a pic when finished.

And yes, with the hemi, tall and narrow white walls, and a gross weight of 1800lbs I'll probably keep it out of the rain!

Ok well I'm almost done, but I've got to run some errands and the closest place that sells caps is 35 min away.

How slow or fast will these blink with a 10k if resistor? I know someone said 3 seconds. Is that how long it takes to recharge?

I'd like to grab a couple other value caps while I'm in the area, just in cases these are too slow.

What would you recommend getting just to have on hand? 6800uf?

Sorry, been out of town, and didn't see your next question.

bwatte wrote:

---

How slow or fast will these blink with a 10k if resistor? I know someone said 3 seconds.

---

The capacitor has nothing to do with the "blink rate". The blinking is handled by the turn signal flasher. Not the relay.

Study how this circuit works again. The relay in it's relaxed state connects that side filament to the brake switch input. The first pulse on the turn signal input charges the capacitor, the relay connects the filament to the turn signal input, and the filament flashes with the turn signal input. The relay is held on continuously duri8ng the turn signal input. Appx 3 seconds after the last turn signal pulse is received, the capacitor will discharge, and the relay returns to the BRAKE state.

I don't think the 10k resistor has much, if any, influence on the circuit because the relay coil is only 87 ohms and will affect the capacitor much more than the resistor.

You want the capacitor to be big enough that the relay coil does not drop-out prior to the next turn signal pulse arriving. If the OFF time of the flasher is say 2 seconds, then the capacitor timing has to be at least 2+ seconds. It really doesn't matter how long it takes for the relay to drop out. The other side will be in BRAKE mode, so it's not like the car is without brake lights for 3 seconds. Again, the relay does not change state during the turn signal event. Only at the very beginning, and 3 seconds after the last pulse ends.

As I said, I've used this circuit, with the 10K Mf cap, and I liked the timing with electronic flashers. Seemed just about right.

I have no idea if 6.8 will give a long enough on time. Give it a try, I guess.

Well I got it all working, but ended up going with the 2 relay setup per side. I made some nice, small stainless brackets that utilized the existing quarter panel bolts to hold the bracket in place.

The relays are in the very back corners in the trunk, so unless you stuck your head inside and then looked back towards where the brake lights are, you'll never see them.

The reason I didn't go with the single relay with 10k capacitor is because I couldn't find a 10k capacitor anywhere, no electronic supply houses or surplus stores etc. I did find some 4800 caps, but by the time I put 2 of those in line it was just real bulky. I liked the idea of having a small bracket that both relays bolted securely to.

Everywhere I went people kept asking why I didn't get a rv trailer brake adapter. But I just think these relays are too cool and never knew they could do so many different things.

I appreciate the help and look forward to learning more from all of you.

I still have a few relays left so I'm brainstorming what else I can use them for, security, accessories etc.