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Post Info TOPIC: Wiring headlight relays into our old cars.


A Poncho Legend!

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Wiring headlight relays into our old cars.


With the recent discussion on dash electrical issues, the topic has come up about wiring in relays for headlights (for safety reasons).

I did this on my 66 GP a little while back, and Jmont64 asked me how I did it. I thought maybe I should post it on here in case others are interested. Keep in mind, I am NOT a mechanic and never claim to be an electrical guru but the lights all worked when I was done so it must be right!

Supplies needed-

2 Relays with pigtails.(I bought 40 amp relays.) Buy 'em anywhere, auto parts stores, Canadian Tire etc. My relays are 5 pin. You only need a 4 pin but 5 pin is more common. It works fine, one pin just doesn't get used. If you don't use it, remove the wire from the pigtail because the middle pin on the relay, which is the one you won't use (#87a) is live all the time as soon as you put the 12 volt power wire on the relay.

12 gauge wire. I think I used about 2 feet. It needs to run from the horn relay to the relays you are adding. On most 60's GM's, the horn relay is on the rad cradle, driver's side.

A terminal for the 12 gauge wire to connect to the horn relay.

Solder and heat shrink if you want to do this the proper way. I likely used about a foot or so of heat shrink.

Mount your relays as close to the horn relay and headlight wires as possible. I hung mine on the cradle above the horn relay.

To wire it up---

-Use a test light and find which wire from the dimmer switch feeds the low beams. Make a note of the colour. Now do the same for the high beams.

-Unhook the battery power to the car.

-Locate the big wire from the battery to the horn relay. It should be a heavy wire, likely red. Make sure there is a fusible link where it leaves the battery or you won't have any circuit protection for your headlights.

-Take the power wires that feed both relays (on my relay pigtail it was the red wire, it goes to #87 on the relay) and join them, then connect the joined wire to the same spot where the battery power goes to the horn relay.

-Take the power wires that exit both relays (on my relay pigtail it was the black wire, it goes to #85 on the relay) and join them, then connect the joined wire to a known good ground.

-Decide which relay is for the low beam. Locate the wire that runs from the dimmer switch to the low beam lights and snip it in the correct spot that it can reach the relay with both sides of the cut wire. After it's cut, the side that comes from the dimmer switch will connect to #86 on the relay. On my relay pigtail it was the yellow wire.

-Take the other side of that wire that you cut and connect it to #30 on the relay. On my relay pigtail that wire was blue. This is the wire that will feed power to your low beams.

-Now do the same for the high beams. On the other relay, connect the wire from the dimmer switch to #86 and the wire that feeds the high beams to #30.

Hook up the battery and test!

Relay before.jpg

After relay revised 001.jpg







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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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Sorry the second picture turned out so crappy. I'm not sure what happened but the important part, the relays, seem to show up well. The rest is the same drawing as the first picture.

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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This is the relay(s) and pigtail I used. The pigtails have rails molded in to the sides so they lock together. There's only one relay pictured but obviously I plugged a second one in to the other pigtail...!

I bought these off ebay. I think I paid about 24 bucks for 10 relays and pigtails total.

DSCF0598.JPG

DSCF0599.JPG

DSCF0600.JPG

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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Great write up Carl! You covered all the bases, no more high amperage going through the headlight switch. Do you think a fuse between the horn relay to headlight relay should be put in?

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A Poncho Legend!

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As I say, I'm no expert but I was thinking the fusible link at the battery (on the wire that feeds the horn relay) is enough. Do you think that is not sufficient?

It certainly would be simple enough to put a fuse or a breaker on the wire off the horn relay that feeds the headlight relays.

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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Yup, forgot about that, unless someone has played with wiring before hand as with mine.

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Canadian Poncho Superstar!

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Thanks Carl, that will be great to follow.

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Jerel


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Thanks Carl ... I'm going to print these diagrams up.



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'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.



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You can also buy "plug and play" kits on ebay. I bought one for my Cherokee and had it installed in about 20 minutes. The one I purchased also had ceramic plugs for the headlights in case you ever want to install high powered lights. Whether you do this from scratch or a kit it's a no brainer. It saves your headlight switch and your headlights are much brighter. It also doesn't hurt to keep a spare relay in the car in case one fails.

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Canadian Poncho wrote:

It also doesn't hurt to keep a spare relay in the car in case one fails.





Good idea. However, even if one fails, you still will have either high or low beams to run on so at least you won't be stuck without any lights.

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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This will do exactly what you need to do. These are just 4 pin relays but for most relay applications that is sufficient. You only need the 5 pin if you are installing a relay application where there is power to either item A or item B, depending on the position of the relay. In the headlight case, your relays are either off or on so 4 pin is fine.

http://www.ebay.com/itm/10Pcs-Iron-Duty-Car-Auto-12V-40A-40-AMP-SPST-Relay-4-Pin-4P-Socket-4-Wire-/251719077337?hash=item3a9ba04dd9&vxp=mtr

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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A 20 amp inline fuse at the battery feed would be your saftey net in the event of an excessive draw from the headlamps....

Also keep in mind, generally, it is the high beam circuit that suffers most with the quad headlamp setup... the low beam circuit would be fine... But, nothing wrong with doing both...



-- Edited by 67Poncho on Sunday 8th of February 2015 09:21:25 AM

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And by the way, I am not endorsing that seller on ebay, I am simply showing a sample of those relays on ebay.

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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Before you get critical on how messy my car is under the hood, I am focusing on function to get this car on the road. Once that happens I will get to the detail part!

Anyway, this shows my setup. You can see the green wire goes in and out of the right relay, brown wire in and out of the left relay.

Also, the red down and to the right is the power wire off the horn relay that goes to both headlight relays.

The black wire under the shiny screw to the right of the relays is the ground wire for both headlight relays.

DSCF0602.JPG

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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Excellent choice of matching relay mounting bolts!!! Recessed head bolts, or whatever the correct name is, look right at home and factory in engine compartments.

Thanks
Randy

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Great write-up Carl! Thanks.

It's probably the best "bang for your buck" that we can do for our cars. It worked wonders for my lamps.

I went a step further and added an internally regulated 12SI alternator, and a HD central powerpoint. The horn buss take off was eliminated. I used Littlefuse brand fuses off the buss to power the relays and lights. Crappy tire sells them. You can see them below the relays.

The good ground connection is to the left of the horn relay.

3 years and a trouble free.

relays.JPG



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67' Grande Parisienne. Ex Ottawa USSR Embassy car, 67- 68.
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Interesting post!!    Thanks..  I'm saving it and the photo......    btw   Is it as important, if you never use your headlights ?



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Carl Stevenson wrote:

Before you get critical on how messy my car is under the hood, I am focusing on function to get this car on the road. Once that happens I will get to the detail part!


DSCF0602.JPG


My engine compartment is just as "messy" at the moment.

I'm not being critical ... because I know you are conscientious and meticulous when it comes to wiring Carl, so I know you are going to put a grommet in the firewall hole.



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'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.



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cdnpont wrote:

Great write-up Carl! Thanks.

It's probably the best "bang for your buck" that we can do for our cars. It worked wonders for my lamps.

I went a step further and added an internally regulated 12SI alternator, and a HD central powerpoint. The horn buss take off was eliminated. I used Littlefuse brand fuses off the buss to power the relays and lights. Crappy tire sells them. You can see them below the relays.

The good ground connection is to the left of the horn relay.

3 years and a trouble free.

relays.JPG





Oh sure, post up a picture of your perfectly detailed underhood in MY thread!!! (Just kidding of course Mark, thanks for the pic) biggrin

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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GLHS60 wrote:

Excellent choice of matching relay mounting bolts!!! Recessed head bolts, or whatever the correct name is, look right at home and factory in engine compartments.


Thanks

Randy





One of my pet peeves when I look at cars in a show, bolt heads with the slot in the head for a screwdriver..... no

Funny thing was, I had to dig a long time in my bolt tray to find those. Some of the ones I found had the slotted head!!!

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


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And the red-circled flexible convoluted conduit (GM term for that loom!) won't be staying either, nowhere near period correct. I picture that as being later 70's or newer. Sometimes a guy has no choice but I have something different for that area.

loom.jpg

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1966 Strato Chief 2 door, 427 4 speed, 43,000 original miles


Canadian Poncho Superstar!

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Carl Stevenson wrote:



One of my pet peeves when I look at cars in a show, bolt heads with the slot in the head for a screwdriver..... no


 Like the ones for joining stove pipes.



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'64 Parisienne CS "barn find" - last on the road in '86 ... Owner Protection Plan booklet, original paint, original near-mint aqua interior, original aqua GM floor mats, original 283, factory posi, and original rust.



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Thank You for the detailed article, will probably add a relay into my convertible top circuit too

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No Bike Mike

1968 Parisienne 2+2 Convertible

1999 Lincoln "Round Car"  (Sadly Sold)

2005 GMC K1500 



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Gasonmiles wrote:

Thank You for the detailed article, will probably add a relay into my convertible top circuit too


 x2..doing my wiring now behind the dash. safety start relay,reverse light relay, finjection uel pump relay, ignition on relay supplying fuse panel with kill switch, convertible top relays because my existing switch is a bit sad and won't take the current, headlight relays, electric thermo fan relay, autronic eye relay...time consuming....hardest part is finding a spot which is eaily accessible once the dash goes back together and accessories mounted!



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cutting a roof off a four door is NOT a convertible.....

65 Parisienne convertible project.



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image.jpgGreat posts everyone and good timing. We must all be on the same page for winter work ( here in Manitoba anyway). I am just in the process of converting my gen. power to alternator. At the same time I am installing relays for the headlights and adding an extra fuse panel to clean up some inl-line fuses. I picked these up at Princess Auto. The fuse block individual led's will light if a fuse blows. I think the relays were about $9 and the fuse block $24. I will also be looking for a power block. Thanks, good tips.



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Some is good...more is better"

Jim Pusiewich

1962 Pontiac Parisienne Conv.

1926 Ford Model T Coupe ( Sold )

1972 VW Super Beetle Conv.

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