H-4's

[DUFFER]

Do I need to install relays or make wiring changes to install H 4's with 60/55 W bulbs on a 67-912 ?

[Peter Graham]

No; headlight power is already routed through an OEM relay which controls high/low beam operation (as long as nobody has rewired your car). I have a '68, run 80/100W bulbs and have had no issues in 17 years. FWIW, I also run a pair of Cibie 45's running 100W H1's connected to the high beam power source via an add-on relay.



Of course there are others who will say relays are cheap insurance to protect the contacts in the headlight relay...

[DUFFER]

Thanks for the info , Jim

[C. Clark]

Check here also,
Replacement Headlight Sources

[Sarastro]

Ummm...hate to be contrary, but the 67 doesn't have headlight relays; I believe that the later cars do. It's a good idea to install them, even if you don't do anything that increases the current in the headlight circuit. The lights will be brighter and the switch will last longer. The installation requires only a couple of $4 relays and some wire.

[Peter Graham]

Good call, Sarasota! I stand corrected: after looking at the PET, it looks like headlamp relays became standard in '68. Sorry for any confusion my confusion caused...

[eki912]

If you want to get all output from your H4s, it is highly recommended to use proper relays and thick enough wiring straight from battery. To prevent any loss.
Do not forget the fuses ...

[Jaems]

I have used the original Euro factory Hella H-4 for 46 years and have no problems. I do not know if there would be a problem with the Bosh H-4 system. The factory did not go to Bosch until 74.

[rockerarm]

Things to consider are age of the wiring and related components, oem wire gage for the intended wattage of the bulbs, and voltage loss to the bulbs during use. If you have any doubt perform a voltage drop from the battery positive to the back of the bulb. And again from the negative side of the bulb to battery ground. On a 40 yo car, I'd guess there are some voltage losses that should be remedied. Even with the standard H4 bulb, light output can be poor on some cars. I've had it happen on my daily driven 74 VW. But with relays and added wire I have a reflective range of 1000' with cheapo H4's. I had a +2v voltage drop and even with H4's lite output was poor. Daniel Stern lighting has a very nice site with good info.
Hope this helps, Bill.
Let me know if you want help with a voltage drop test. Easy stuff. I'm local to you.