55.2-59 Wiring Relays for Turn Signals/Parking Lights

[daveshilling]

I'm wiring up the headlight relays, and they're relative straightforward, but the parking lights/turn signal combos, that one is giving me a headache. Maybe it's just not worth the hassle to have the parking lights on a relay, I just think it would be cool to have them a bit brighter (tail lights too!)

What I'm looking to do:

(All fresh wiring, zero factory copper) Using the factory headlight switch:


Switch in position 0: turn signals function and get 12v from the battery via relay, but no parking lights.

Switch in position 1: parking lights on, 12v from the battery via relay, turn signals interrupt the parking lights

Switch in position 2: headlights on, parking lights on, 12v from the battery via relay, turn signals interrupt the parking lights

Right now, I'm triggering the headlight low and high beam relays with the respective wires that would just normally go to the lights themselves. I have 3 more wires left in the EZ-Wire kit... parking lights, turn signal left, and turn signal right.

Any thoughts? Scrap the parking light relay nonsense?

[leegreen]

single or dual element park/turn bulbs?

I used dual element front and rear. Low element is park, comes on with switch out one notch, no relay. High element is brake & turn, wired via 90s GM column.

low beam and high beam both on separate relays. A 3rd relay for driving lights that will only come on with hi beams + a toggle switch

I'm using a factory headlight switch too, but not wired as per original, the headlight switch as I wired it has no function in the wiring of brake and turn.

[dsraven]

what are you trying to end up with? headlights that turn off the respective headlight when that signal is called for? just brighter lights with less load on the headlight switch?
if you want brighter lights go for the LED style, run a (fused of course) relay for each headlight beam-low and high- and a relay for tail and a relay for front marker. you could run a relay for the signals too if you like wiring stuff that much, lol.

[leegreen]

A flasher is a relay, seems redundant to relay a relay

[dsraven]

if you run an LED bulb then you may need to look at the flasher unit as the old fashioned flashers used a bi-metallic strip inside them that relied on the current needs of the regular bulb to heat up the bi-metallic striop and cause the contact points in the flasher to seperate, then the strip would cool off and the contacts would contact again and the whole process starts over again. with the LED bulbs there isn't enough current draw to heat up the strip so the signals just come on steady-no flashing usually, or they hyper flash with a possibly newer style flasher. a solid state flasher unit fixes that. some of those need a ground to the flasher as well.

https://www.grote.com/warning-hazard...ronic-flasher/

https://www.velvac.com/products/fuse...asher-provides

this one gives an audible clicking sound
https://www.larsenlights.com/electro...-flasher-relay

this site shows how to wire a flasher relay
https://www.grote.com/warning-hazard...-pin-flashers/

another wiring diagram for flasher relays
https://www.google.ca/url?sa=t&sourc...iUVNyyFpAKHNux

hope that helps somebody. important to remember the flasher is wired into the circuit before the signal switch. it becomes th power for the signal switch.

[dsraven]

https://www.motortrend.com/news/ligh...-flasher-leds/

[mr48chev]

You shouldn't need relays on park or turn lights.

The reason for relays on Headlights is that a lot of us use Halogen lights that draw more amps and a number of us use high powered Halogen lights that draw even more power than just the Bright 7 inch Sylvania from the parts house. I ran 55/100 watt bulbs in my 71 GMC that draw a lot of amps and before I put in the relays ate dimmer switches with abandon.
Turn signals don't draw many amps as a norm and tail and park lights don't draw many amps.

You might need relays on the tail/park lights if you light the truck up like these bull haulers who deliver cattle to Agra Beef here in town do though they look like Christmas trees rolling past the house at night.

[daveshilling]

Thanks all for the input. I'm going with regular Halogen Bulbs, and the relays allow them to be brighter and avoid putting so much amperage through the 60 year old factory headlight switch. LED's are great, but I like how Halogen looks on an old ride.

This is very common practice with headlights, so I figured what's good for the goose is good for the gander, right?

mr48chev, I may have to just do a test and see how bright they are on battery 12v vs through the headlight switch. To your point, they are much smaller so it may be just fine through the switch.

[franken]

Originally Posted by leegreen

A flasher is a relay, seems redundant to relay a relay

Traditional flashers are certainly not relays. You can't run a relay with two connections.

[leegreen]

Originally Posted by franken

Traditional flashers are certainly not relays. You can't run a relay with two connections.

good point, you got me there!

to try harder at the point I was thinking about: bright lights require enough current. The contacts inside the flasher are probably not the limiting factor and heavy duty flashers are cheap. A flasher driving a relay sitting beside it probably does nothing for you except increase complexity in a typical turn signal setup. Reflectors in the light housings, wire size to lights and ground quality at lights would be my first targets. Wire size to switch and switch quality would be next.

[daveshilling]

Originally Posted by leegreen

good point, you got me there!

to try harder at the point I was thinking about: bright lights require enough current. The contacts inside the flasher are probably not the limiting factor and heavy duty flashers are cheap. A flasher driving a relay sitting beside it probably does nothing for you except increase complexity in a typical turn signal setup. Reflectors in the light housings, wire size to lights and ground quality at lights would be my first targets. Wire size to switch and switch quality would be next.

I don't think the flasher was ever a point of concern here, really. Switching to a relay makes it even less of a concern, as it would never be under any significant load.

Switch quality is not a variable, its the factory Delco headlight switch, so my aim was to prolong the life of this switch using inexpensive relays and heavier gauge wiring I already own.

Thinking about it more, and looking at the wiring schematic for the RPO signals offered by GM for 55-59's, only one wire is sent out to the parking lights, so I guess each of those wires changes from a direct 12v power source to a 12v signal wire.

I think perhaps I will leave the front parking lights alone and run them off the switch, and maybe look into a warmer LED bulb option if there is one for the parking/brake housings only.

[daveshilling]

Originally Posted by dsraven

...if you like wiring stuff that much, lol.

yes, I'm one of those people that doesn't mind wiring (= When I look at trucks for sale, the very first thing I'm looking at is wiring. If someone does that poorly/in haste, what else did they do like that? Wiring is something that is very inexpensive to do better, yet so frequently guys seem like they went out of their way to make it look bad and save $20.

I'm not like a crazy perfectionist, but wiring is a peaceful activity and its one of the only things that I can make nice without spending much more.

[mr48chev]

Originally Posted by daveshilling

Thanks all for the input. I'm going with regular Halogen Bulbs, and the relays allow them to be brighter and avoid putting so much amperage through the 60 year old factory headlight switch. LED's are great, but I like how Halogen looks on an old ride.

This is very common practice with headlights, so I figured what's good for the goose is good for the gander, right?

mr48chev, I may have to just do a test and see how bright they are on battery 12v vs through the headlight switch. To your point, they are much smaller so it may be just fine through the switch.

This is a chart on watts and amps for what we normally use for stop, tail and turn bulbs Note that the brighter 2357 bulb draws .59 amp on the tail/park side and 2.23 amps on the stop/turn side. That's not much draw through a wiring system. If you have led stop/tail lights the draw is less yet.

I have LED replacement headlight bulbs in my BMW and they just throw a white light. I wouldn't have those ugly bug eye (current fad for old trucks) 400 dollar lights in anything I owned. They are just flat too ugly.

[Second Series]

Originally Posted by daveshilling

Right now, I'm triggering the headlight low and high beam relays with the respective wires that would just normally go to the lights themselves. I have 3 more wires left in the EZ-Wire kit... parking lights, turn signal left, and turn signal right.

Any thoughts? Scrap the parking light relay nonsense?

I think you could wire up relays for the last 3 wires the same as you did for the headlights. The wire to the parking lights-cut it, attach the cut end from the switch to the relay control, attach the cut end to the lights to the relay contacts. Add fused 12v from the battery, and Ground. Be aware of how the switch is working to determine how to connect, is it providing 12v to the load or is it grounding the load?
Same for the turn signals, but put the relay before the flasher unit.
I like to make a diagram usually for this kind of thing, hope it helps.

[1project2many]

Headlight and park light relays are fairly basic. 12V from light "high/low beam" switch will power the relay coil while the light circuit receives power from a dedicated 12V wire to the relay contacts. Brake and turn could be a little more tricky depending on whether you're using "Dual filament" simulating LED's or LED's set up as separate lights. Front and rear turn signal switches are on separate circuits. Rear circuit is integrated with stop lamps so simulating a factory circuit layout requires a little more planning. Front signals can be wired like headlight and park lights. Wire from turn signal switch provides 12V signal to relay while light power comes from 12V supply at relay contacts. Brake / turn combination requires three relays. Relay one coil is powered when the brake pedal is pressed. Relays two and three are controlled by the turn signal switch. Here's where attention to detail is required. Constant 12V should be connected to the common terminal of relay #1. This terminal is usually labelled #30. The normally closed contact of relay #1 (87a) should be connected to the normally open contacts (87) of relays #2 and #3. The normally open contact of relay #1 (87) should be connected to the normally closed contacts (87a) of relays #2 and #3. The common pin (#30) from the turn signal relays should be connected to the left and right side turn signals. This will simulate the original design and allow both brake and turn signal to share the same lighting circuit. Of course, if you use LED lights designed to simulate dual filament lights with brake and turn the designers may have incorporated features which make the relay wiring above unnecessary.


Also, plan to use an electronic flasher if you aren't already. There's no way relay coils draw enough current to make an old fashioned flasher work.

[_Ogre]

Imo, relays on anything with new wiring is a waste of time and money.
If you had the original harness, I can see relays would help with headlights. The tail/stop/turn seems to just add a point of failure. I use relays on TRUK for heavy loads, fan and windows or control switching like: cruise control, trans control and similar. New harness just doesn't have the resistance like the old harness.

[leegreen]

How the turn signal switch is designed to work needs to be considered before you plan relays for stop and turn. Some switches integrate the brake lights in the turn switch.

If you are using a newer GM column, the outputs from the brake switch and turn and 4 way flashers go into the column harness and you get back a wires for the turn/brake bulbs at each corner of the vehicle. I have a diagram if interested. Some bolt on turn signal stalks for pre turn signal columns work the same.

If you have a turn signal switch that does not integrate brake lights, one easy way to do it is to get one of those trailer adapter wire boxes that go from a car with separate yellow turn signals and red brake lights to a trailer with combined red brake/turn lights.

In all cases for combined stop/turn, if you want relays for the brake and turn you are going to either relay them before the turn signal and brake switches or relay each corner after the switches with 4 relays. IMO the first option does not accomplish much, you have other problems if you are current limited at the switches. A relay for each corner seems like overkill unless you are wiring for a serious trailer. Put your money and effort into larger gauge wire for the long runs and in making sure grounds a good.

[dsraven]

a lot of the problems I have seen over the years with dim lights boils down to a poor ground. yep, big wires, shiny new switches and connections, solder, shrink tube etc etc, but they didn't account for the other side of the circuit-the grounding. it's the weak link usually. on these old trucks, even if rebuilt (and sometimes that makes it worse because guys don't wanna scratch up the new paint for a ground connection to bare metal) the grounds get forgotten. if the battery is grounded to the body, the frame and engine it is usually the cab that gets the body ground wire attached because thats where the battery is usually. from there the ground relies on metal to metal contact through the cab to fender or inner fender mounting hardware and then rad support to fender mounting hardware (if the headlights have a ground wire to the rad support) and then the headlight bucket to fender mounting hardware etc etc. you can easily see why the circuit may have resistance built in to the ground side. it is best to run a dedicated ground wire from each light to a nice shiny bare metal spot on the frame rail of the vehicle as the frame runs from one end to the other and is better than any wire could be. then ensure the frame rail also has a battery ground cable attached to a nice shiny bare metal spot. when done all the wiring and it tests good then go to these spots and apply some anti corrosion.

[daveshilling]

Originally Posted by dsraven

a lot of the problems I have seen over the years with dim lights boils down to a poor ground.

Yeah that's a great point, compounded by the fact that the ground for the parking lights is just the housing itself, there is no ground wire whatsoever... so maybe adding a ground wire from the frame rail to the housing to ensure the ground is reliable would be a good idea.

I think I'm going to skip the relays for running lights, make sure wires are stout and grounds are reliable, and see how it goes.