I used to make one up and sell them for GM g bodies and yes it makes a difference. There is allot of voltage drop in stock wiring and switches.

Basically the existing switch and wiring just operates a relay. The relay is fed directly from the battery. This reduces the voltage drop and does make a difference in lighting especially if you have halogen or modern halogen units that use H4 bulbs. The pinout on the H$ bulb has two pins swapped around from old style bulbs.

Also beware of some of those kits as many use really thin wire and cheap relays. I usually use a 12ga feed and 14ga to the bulbs.

 

is "H4" compatible with the old school headlights with what looks like a 220 house plug with the big flit pins.

 

very worth it. In fact I did my horns as well. and of course my electric fan

 

Was your relay mod fan something you purchased as a kit or you created !

Thx

 

Yes they will absolutely help your standard headlights!

I was wondering about just how big of a difference they could make, so when I did mine I took pictures and started a thread on it:
https://forums.vintage-mustang.com/vintage-mustang-forum/1120258-headlight-relays-wow-pics.html

Lots of detail on how they help over here:
Daniel Stern Lighting Consultancy and Supply

 

I did it and notice a difference in my headlight brightness. Also, I did it for, if nothing else, it taking the "amp load" off the switch.

 

Yes definitely worth the upgrade, but the price point can be prohibitive. It was for me. We ran across a painless wiring headlight conversion kit at a swap meet. My brother grabbed it for 30 bucks. It normally is close to 200 from painless. We installed with standard headlamps. Major difference. Definitely much brighter. I have had people “flash their headlights” at me when the brights were on. Before the upgrade, I had to drive with brights on just to see the road, and was never flashed for my brights.

 

West Coast Classic Cougars has a great kit that installs with all original connectors so no wire splicing and can be removed at anytime to allow the lights to function as they originally did. I just installed this on my 70 Mach 1 with some Hella H4 housings and love how much light they throw off. Def worth the money for the upgrade!!!

https://secure.cougarpartscatalog.com/100022594.html?attribs=80

 

This kit uses the original wires and connectors to the headlights.
I installed this kit from NPD: # 11653-1B. It has larger gauge wires and ceramic connectors. However, this design has only one fuse for both hi & lo beam. I cut the power feed wires and used two fuses using a block similar to this: https://www.summitracing.com/parts/sum-900375/overview/. I also feed the power to the DuraSpark relay off this block.

 

I bought relay kit referenced in the thread below from Amazon. Installing now. (Proud of my little bracket and mounting)

https://forums.vintage-mustang.com/v...l#post10054962

 

I did this conversion last year, best $120 I've spent in a long time. I used the E-spec Cibie housing with a standard 60/55W Hella H4 bulb. The relay kit simply plugs into the original passenger side headlamp socket and is only used to energize the relays. The relays get power for your headlights directly from the battery. The light spread on these housings is excellent, and with the relays you could use a higher wattage bulb.

Relay kit
https://www.amazon.com/gp/product/B00Q3UZY6G/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Cibie/Valeo housings
https://www.amazon.com/CIBIE-HALOGE...HES/dp/B079J5VG1Y/ref=sr_1_1?keywords=082440&qid=1559960114&s=automotive&sr=1-1

Hella H4 bulbs
https://www.amazon.com/gp/product/B00IKM61MQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

Depends on your definition of "worth it". If you add relays here is what you'll get:
a. Increased voltage (potentially) at the lamps as the "supply" voltage doesn't have to go all the way to the switch, through the dimmer switch and back to the lamps.
b. "Potentially" because the final voltage is subject to the resistance in the wiring, relays and connectors. When I do these I use a heavier gauge wire, quality relays and solder all wire connections.
c. Because full current isn't going to your headlamp switch the built-in circuit breaker will be ineffectual, so your relay circuit needs to be properly protected.
d. If your headlamp circuit was crappy before, adding relays will just make it "remotely crappy". Fix the main issues first.

Also, FWIW, halogen headlamps are much brighter than incandescents and do NOT, generally, draw any more amps.

 

For your viewing pleasure...

 

I went the relay route on my 67 when I installed H4 headlights plus two H4 lower valance “fog” lights operating in the same circuit. Alternatively, if you are looking for better night time vision, on my wife’s 66 I installed the Hella H4 lenses (much better beam quality than the cheapy ones on my 67) and a set of LED H4 bulbs. The LED’s use less than half the wattage of the halogen and produce the same amount, if not more, light. The brightness of the LED will not fluctuate with voltage as happens with filament bulbs. I have used these LED bulbs on two of my vehicles so far with great success...
https://www.amazon.com/Auxbeam-Head...p/B074GZ3S4P/ref=mp_s_a_1_4?keywords=auxbeam+h4&qid=1560004034&s=gateway&sr=8-4

Something to ponder ??