Alfa Romeo Forums banner

H4 headlight conversion

7049 Views 10 Replies 3 Participants Last post by  Kiwi 74 Alfa
Hi all.
This is a question for the RHD 1750 GTV (10545 S2) owners who've had to convert the original H1 Outer Lights to the H4 ones.
My problem may be peculiar to the NZ market (and I've this question in the NZ forum) but any and all help appreciated.

I've purchased replacement headlights from the UK but the outer lamps only use the H4 bulb (Hi & Low filaments) rather than the original H1 bulb (single filament). I've been cleaning up the wiring and testing the leads from the column light switch and it appears the outers get power (are on) in both dipped and full (Hi/low) beam modes. I assume this is so all 4 headlights operate in full beam mode.
Can anyone please confirm that this is correct (or describe their cars operation) so I can get my wiring correct.
The electrical diagrams I have don't cover this setup

My plan is to run the full beam lights through relays (as there are now 4 - the 2 H1 inners & 2 H4 Hi outers) which is reasonably simple to setup, but the problem I'm facing is that when using full beam, the outer lamps will have both filaments operating at the same time (with the hi/low feed from the column switch). This will produce over 115 Watts per lamp which is too much for the lamps to handle for any length of time.

So My question is; Other than retaining the original operation (by not connecting the H4 Hi beam filament), How do I isolate the Hi/low feed from the column switch to turn the dip beam off when running the Hi beams?

My thoughts would be to have a 'normally on' relay connected to the supply of the Low/outer circuit with the inner/hi beam circuit feeding the relay switch. This (in theory) would cut the power to the outer circuit when the inner circuit is activated.
Confused? Maybe I need to draw a diagram ?

Thanks to all
1 - 11 of 11 Posts
If I understand what you're after correctly, the way the relays are set up in the attached will give the desired results.
(wire colors and some other items aren't neccisarily correct for your car, but the relay circuts from switch to headlights will definitely bring it)
See less See more
Thanks Tifosi - Your diagram is exactly what I'm planning for the power supply to the lights and hopefully what the final configuration will be.

My problem (sorry I can't/didn't describe it well) is the original light configuration was 1 filament (H1) per lamp.

On low beam just the outers are on, on Hi beam the outers stay on and the inners turn on (giving the 4 beams). This as acheived by the low beam supply/switch staying on continuously (ie on in both Hi and Low switch positions).
This is the same as your 'Grey' wire being live in both Hi and Low modes

I need to isolate the low beam circuit on the Hi beam setting otherwise the heat generated from the 2 filaments in the outer will cause problems and the certification inspection will reject the lights as both Hi or low in one lamp cannot be on at the same time except intermittantly for flashes (also the alternator is probably under powered - but that's for another thread).

Still think a normally closed relay on the low beam circuit should work (ie through the 87a terminal), and switched of by a feed from the Hi circuit

See less See more
If you've currently got H4 in the outer positions and H1 in the inners, the above diagram will bring it.

Low beam (gray) will activate only the outboard lamps low beam filament, then when the switch is thrown to high beam (green) the low beam on the outers will turn off and all 4 lamps will come on. High beam filament in the outers, single filament in the inners.

Or is there something in your switch that causes the low beams to stay on continuously regardless of the high beams being selected or not?
If so, I'm not really sure how you'd get it done, though your thought regarding an 87/87a type relay may indeed do it but it'd be a little more complex than what's shown above.
The NZ vehicles originally had/have single filaments (H1 bulbs) per light, so to get all 4 lights on (HI beam) the outers stay on (continuously) and the inners switch on (or off) to suit.
The replacement outer lights only take H4 bulbs so I have to rewire.

I'll fit the 87a relay on the Grey feed, switched from the green.
and since the whole loom is out of the car it will be easy to test (and experiment with)

Thanks for you help Tifosi

Here's a really quick~n~dirty scribblin that should be right then as your lo beam circut has power all the time regardless of switch selection.
Note that the low beam is pretty much a standard hook up and powered through the switch, except that it passes through an 87/87a type relay on its way to the lights.

Throwing the high beam switch will cause the 87/87a relay to turn off the low beam filaments and in turn activate the 87/87 type relay where all four high beam filaments will come on and be power serviced from a stout source not through the switch proper.
(making for better switch longevity, which is the purpose of the relays to begin with)

And purely for 'safety' and not shown in the drawing, where the 87/87 relay shows one terminal going to both left lights and the other going to both right lights?
If you were to have one terminal going to both outer lamps and the other going to both inner lamps, should there be a partial failure in the relay itself you would at least have 1 high beam light on each side of the car functional as opposed to 2 on one side and none on the other.


See less See more
Thanks again Tifosi - it's really great to have someone who has an interest and the knowledge to help.
I'm mapping the wiring and will try to produce a diagram for the 10545 series. I some diagrams that Papajam supplied but only have autoCAD (drafting software). What's the software you're using? Might speed things up /help me out.

Software I'm using?

None. I draw by hand in Adobe Photo Deluxe. But then I don't do whole cars, or even sections of them, just little bits here and there that aren't covered in the conventional diagrams like headlight relays, starter relays and a couple other oddities that aren't part of the standard setup.

Dunno what papajam uses on his artistic miracles though other than they end up going out the door as pdf files.
I like your idea of getting all 4 on hi beam at once. However, on my 74 2000 GTV I am pretty sure the outer lights are permently dipped and when all 4 lights are on during hi beam it is only the inners that are high. The outers are on but dipped.

I also put relays in to operate both. Was warned in this board that the stalk switch did not like carrying full current.
The original lights operated like that as they only had 1 (H1) filament per light but the replacement outer lights I have require H4 bulbs (2 filaments - high + low).
Thought about simply ignoring the outer high's and leave the system 'stock' (but with relays etc) but figured since they're there, I might as well use all 4 high beams.
I don't want the lows on at the same time to reduce the possibility of overheating. Also over 300 watts of lighting (with them all on) is a bit overboard/illegal? (not to mention the alternator might struggle!)
You are right. High and low on in the same bulb at the same time will overheat things and quickly.
Change over (87/87a) relays can be used for magic things. We use some on our farm equipment. Tifosi's solution of using a changeover relay is nifty and ideal. Just set it up so the default is for the dip lights to be on so that if somthing happems eg the power source to the relay fails you can get home on dips rather than blinding everybody with 4 hi beam lights.

If your hi beams are 60W then four of them will draw 240W. At 12 volts that is 20amps. Tifosi suggestion of a 20A fuse leaves no reserve so will need a higher rated fuse. 20A is quite a high continuous draw and may cause heating in some connections. I would go with two relays on the high beam side, not one. One for the outside pair and one for the inside. That would give you the redunancy that Tifosi was suggesting.
1 - 11 of 11 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.