Headlight Relays with Hidden Headlights

[Big_John]

Concerning relays and circuit breakers I am intrigued by this combo....

Amazon product ASIN B01NBAO1SA
Amazon product ASIN B092CDM26G

While everyone's experiences will differ, it's my preference to stick with the tried and true Tyco/Bosch relays. These may work fine for you, but usually the cheaper knock-offs aren't as reliable.

I'd use the piece that @3175375 suggested though, albeit with Tyco relays.

 

[bnz84]

Yes, the relay plus fuse/breaker application is my interest. This is a better name in this configuration.
Picker PC798-1A-C2-12C-N-X 30A Automotive Plug-In Relay | Waytek

 

[Gerald Morris]

Here guys, these are pure-dee BOSCH SSRs!

BOSCH NORMAL OPEN MINI RELAY 12V 30A 0332019151 - NOS | eBay

If I didn't already have them, I'd jump on this deal. I'm STILL mighty tempted,,,,,

Tyco is still good, but old time Bosch is best.

 

[Big_John]

Is there a wiring diagram for the headlight motorized door controls? I'm not clear on how it's set up. My 74 has a royal front end on it, I have the mechanical bits and motor working, just need the "logic". Thanks

There's two ways to do it.

You get out the FSM, look at the wiring diagrams and figure it out that way. You'll have to source a hard to find (and usually expensive) NOS or used relay and do all the wiring.

Or you can look at post #3 in this thread and you'll see a real simple wring diagram using an inexpensive and easily available Tyco relay. I used the existing wiring colors for that diagram, figuring that most were concerned with adapting this to the original wiring. Here's how it breaks down using the numbered terminal connections on the relay

#85 goes to the switch.
#86 goes to ground
#30 goes to a circuit breaker (20 amp would work fine) and then to power.
#87 goes to the "open" motor terminal
#87A goes to the "close" motor terminal

 

[74monacoHT]

There's two ways to do it.

You get out the FSM, look at the wiring diagrams and figure it out that way. You'll have to source a hard to find (and usually expensive) NOS or used relay and do all the wiring.

Or you can look at post #3 in this thread and you'll see a real simple wring diagram using an inexpensive and easily available Tyco relay. I used the existing wiring colors for that diagram, figuring that most were concerned with adapting this to the original wiring. Here's how it breaks down using the numbered terminal connections on the relay

#85 goes to the switch.
#86 goes to ground
#30 goes to a circuit breaker (20 amp would work fine) and then to power.
#87 goes to the "open" motor terminal
#87A goes to the "close" motor terminal

It appears the factory setup relies on limit switches at the motor, not timing or current sensing. Would still like to see the wiring diagram so I can ponder my options as I have an aftermarket motor without limit switches.

 

[Big_John]

It appears the factory setup relies on limit switches at the motor, not timing or current sensing. Would still like to see the wiring diagram so I can ponder my options as I have an aftermarket motor without limit switches.

The limit switches are contained in the factory motor. Honestly, I've never heard of an aftermarket motor being used (or even available) for this.

Once you get into "aftermarket" components that don't function like the OEM stuff does, you are really on your own. To see how the factory wired it, get a Factory Service manual and study the wiring. While this site does not have a '74 FSM, it does have some years that are close enough to show how the factory wired it. Service Manuals – MyMopar

The factory wiring is pretty simple though.... One wire has power to close and one to open. Turn the lights on and current flows to the motor and stays on (the limit switches stopping current) until you turn the lights off and power goes to the motor to close. There is no current sensing or anything like that.

If I were you, I'd ditch the "aftermarket" motor (if indeed it is) and find a OE motor for it with the limit switches in place.

 

[thethee]

One thing about the connectors, they really aren't made for doubling up the 12 gauge wire or using the 8 gauge. You may need to solder these connections. If there's a source for larger gauge connectors, I'd love to hear about it.

Hi John,
Started working on this mod this past weekend and the connectors I have for the relays sure aren't made for the doubling up. The metric wire I have is more like 11 gauge which isn't helping. You mention soldering the connections, but instead of making a mess soldering two wires onto the same connector I was thinking of having a single wire in the connector and then splice the double into that. Any thoughts on that?

 

[3175375]

Hi John,
Started working on this mod this past weekend and the connectors I have for the relays sure aren't made for the doubling up. The metric wire I have is more like 11 gauge which isn't helping. You mention soldering the connections, but instead of making a mess soldering two wires onto the same connector I was thinking of having a single wire in the connector and then splice the double into that. Any thoughts on that?

Make sure that the single wire size (gage) is big enough to carry the currents, then you are good.

 

[DDR2467]

View attachment 131456

View attachment 131455

Hi John,
Great post. A while back i had an issue with the Putco harness I bought. Couldnt get it to work with the headlamp doors i have on my '69 300 convertible even with the fix that someone had posted i had issues so... on to this post. I ordered all of the items you have listed here but have a couple of questions i was hoping you could clarify.

1. You seem to mention only 1 extra Tyco relay for the headlamp doors under your dash but the picture that followed seems to show 2 relays.
2. At the bottom left of the diagram it shows three arrows with "Existing 16 Gauge Wire", "to Dimmer Switch", and "12 Volt Source" as labels... I obviously understand the "12 Volt Source" but i would like clarification on exactly where the feeds to the relays are coming from.

As i recall, when using the Putco harness we plugged the original wiring into the Putco harness. Are we utilizing a wire (or 2) from the existing wiring harness to supply signal to the new relays? Is that where the "Existing 16 Gauge Wire" and "To Dimmer Switch" are originated from?

Thanks in advance for the update John!

 

[Big_John]

Hi John,
Great post. A while back i had an issue with the Putco harness I bought. Couldnt get it to work with the headlamp doors i have on my '69 300 convertible even with the fix that someone had posted i had issues so... on to this post. I ordered all of the items you have listed here but have a couple of questions i was hoping you could clarify.

1. You seem to mention only 1 extra Tyco relay for the headlamp doors under your dash but the picture that followed seems to show 2 relays.
2. At the bottom left of the diagram it shows three arrows with "Existing 16 Gauge Wire", "to Dimmer Switch", and "12 Volt Source" as labels... I obviously understand the "12 Volt Source" but i would like clarification on exactly where the feeds to the relays are coming from.

As i recall, when using the Putco harness we plugged the original wiring into the Putco harness. Are we utilizing a wire (or 2) from the existing wiring harness to supply signal to the new relays? Is that where the "Existing 16 Gauge Wire" and "To Dimmer Switch" are originated from?

Thanks in advance for the update John!

1. Just one relay for the headlight doors. The other relay dumps the oil slick when I'm running from the law.

2. The "existing 16 gauge wire" and "to dimmer switch" are really labeling both the wires. (hey it made sense to me at the time). If you look at the floor dimmer switch, you'll see a red wire and a violet wire. Those would be the two wires to hook to. You can find them under the hood with the red running to all 4 headlights and the violet just going to 2 headlights. I shortened the wiring under the hood, but that's up to you.

Hope that answers the questions.

 

[DDR2467]

1. Just one relay for the headlight doors. The other relay dumps the oil slick when I'm running from the law.

2. The "existing 16 gauge wire" and "to dimmer switch" are really labeling both the wires. (hey it made sense to me at the time). If you look at the floor dimmer switch, you'll see a red wire and a violet wire. Those would be the two wires to hook to. You can find them under the hood with the red running to all 4 headlights and the violet just going to 2 headlights. I shortened the wiring under the hood, but that's up to you.

Hope that answers the questions.

Will look at this weekend but I’m sure it will! You are such an asset to this forum! Thank you for everything you do and share!

 

[DDR2467]

1. Just one relay for the headlight doors. The other relay dumps the oil slick when I'm running from the law.

2. The "existing 16 gauge wire" and "to dimmer switch" are really labeling both the wires. (hey it made sense to me at the time). If you look at the floor dimmer switch, you'll see a red wire and a violet wire. Those would be the two wires to hook to. You can find them under the hood with the red running to all 4 headlights and the violet just going to 2 headlights. I shortened the wiring under the hood, but that's up to you.

Hope that answers the questions.

Is the “floor dimmer switch” the foot operated high beam switch?

 

[Big_John]

Is the “floor dimmer switch” the foot operated high beam switch?

Yes

 

[DDR2467]

Make sure that the single wire size (gage) is big enough to carry the currents, then you are good.

If you want to send 2 - 12 gauge wires into the terminal (as BigJohn recommends), then can you simply use a single 12 gauge wire (maybe a few inches long) to make the connection between the terminal and the 2 wires that there wasn't enough room for in the terminal? I know you said to "make sure that the single wire size (gage) is big enough to carry the currents..." but for an inexperienced person like myself... would this be correct? TYIA! I hope you all realize that these little things we ask are because we are inexperienced and just want to make sure we are doing it right... your knowledge is very much admired and appreciated!

 

[Big_John]

If you want to send 2 - 12 gauge wires into the terminal (as BigJohn recommends), then can you simply use a single 12 gauge wire (maybe a few inches long) to make the connection between the terminal and the 2 wires that there wasn't enough room for in the terminal? I know you said to "make sure that the single wire size (gage) is big enough to carry the currents..." but for an inexperienced person like myself... would this be correct? TYIA! I hope you all realize that these little things we ask are because we are inexperienced and just want to make sure we are doing it right... your knowledge is very much admired and appreciated!

I would use a #10 wire for the single wire or better yet (if it fits) a #8 wire.

If you do the calculations, 2 #12 wires works out to an equivalent of as single #9 wire (which isn't readily available). So you round up to #8. I don't know if the #8 will fit and talking about just a couple inches, the #10 would work. To make the calculation easy: Wire Combination Calculator

Then I would use one of these or something similar (if practical) to split the wires and connect to the relays.

Amazon product ASIN B08BDS8L3N

 

[bnz84]

They make 8ga female spade terminals that would fit both 12 ga. Maybe minor strand trimming.

Amazon product ASIN B0844VWS35
And these too
Amazon product ASIN B094PY7K38

 

[thethee]

I would use a #10 wire for the single wire or better yet (if it fits) a #8 wire.

If you do the calculations, 2 #12 wires works out to an equivalent of as single #9 wire (which isn't readily available). So you round up to #8. I don't know if the #8 will fit and talking about just a couple inches, the #10 would work. To make the calculation easy: Wire Combination Calculator

Then I would use one of these or something similar (if practical) to split the wires and connect to the relays.

Amazon product ASIN B08BDS8L3N
View attachment 558645

Agreed on your calculations about the single versus double connection. However, the thing I'm trying to wrap my head around is, how much current is actually flowing through this? It's kind of hard for me to comprehend what gauge is required and how much is preference.

They make 8ga female spade terminals that would fit both 12 ga. Maybe minor strand trimming.

Amazon product ASIN B0844VWS35
And these too
Amazon product ASIN B094PY7K38

These won't fit inside the sockets for relays and headlights though

 

[DDR2467]

I had a request a while back to do a thread on headlight relays. It's been done before on here, and I'm not doing anything different, although I am covering a relay for the headlight motors too.

You'll need two relays. As I always recommend, go with Tyco/Bosch relays. Don't scrimp and buy the Chinese knock-offs. I buy them from Amazon. Best deal I've found for genuine Tyco relays.

Amazon.com: Metra Install E-123 Bay Tyco Relay 12 Volt 30 Amp Each: Car Electronics

View attachment 131423


Next you'll need two sockets. These are available on Ebay or Amazon.

View attachment 131424

Amazon.com: Absolute SRS105 5-Pin 12 VDC Relay Socket Interlocking Style: Electronics

A 30amp circuit breaker can come from any parts store.

View attachment 131425

Some 12 gauge wire. To match the existing wires, you'll need black, red and purple. Some 8 gauge wire in your choice of color.

Some connectors as needed.
Universal GM Chrysler Ford Female Terminal Connector 14 12 AWG 25 Pack

View attachment 131426

Two bags of Packard 56 connectors. These are the wider connectors for the headlights.

.3125 Wide Packard 10 12 AWG Female Lock Tab Terminal

View attachment 131427

Here's how it's wired.

View attachment 131428

So the .3125 Packard connectors are incredibly hard to locate. The vendor in the link says "out of stock". Would it not be a good idea to dremel a bit of the male spade off the headlamp in order to utilize the very common .25 (6.3mm) width female terminals with the lock tabs? Also for clarification, we should be reusing the 2 prong and 3 prong factory insulators that connect to the backs of the headlamps correct?

 

[Big_John]

Agreed on your calculations about the single versus double connection. However, the thing I'm trying to wrap my head around is, how much current is actually flowing through this? It's kind of hard for me to comprehend what gauge is required and how much is preference.

You can figure that out using the wattage of the bulbs and ohms law. IIRC, low beam bulbs draw 55 watts and high beam 60 watts. Don't forget to double it (2 sets of lights).

What you are aiming for is minimal voltage drop from the source to the headlights. There are other reasons, like taking the load off the switch, bulkhead connector and the old wiring, but by doing those things, it still results in minimizing voltage drop for brighter lights.

IMHO, the #12 wire is probably overkill. The factory feed of #16 wire for 2 headlights did the job, but what I've done is feed the individual lights with #12 wire. Do some math and you'll find it's probably more than you need. But I'm not worried about saving 45 cents per car like the factory did, and I error on the side of larger wire. Remember that wire that's too big will never hurt anything... But wire that's too small will.

 

[Big_John]

So the .3125 Packard connectors are incredibly hard to locate. The vendor in the link says "out of stock". Would it not be a good idea to dremel a bit of the male spade off the headlamp in order to utilize the very common .25 (6.3mm) width female terminals with the lock tabs? Also for clarification, we should be reusing the 2 prong and 3 prong factory insulators that connect to the backs of the headlamps correct?

I wouldn't do that. I'd push on the smaller connectors first. (had to do that once, so it does work, but not really recommending it)

I reused the insulators.