adding turn signals with brake lights

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.