To relay or not to relay? H4 Headlight question

[geshaghi]

I've purchased a set of H4 headlights for my 72T. I've received conflicting advise on installation. Some say just plug and play, and others have said install a relay. Is there a consensus on whether a relay is needed and what the benefit would be? Also, the lights I purchased have what looks like an auxiliary connector below the 3-prong plug - any idea what these are for? Thanks

[imcarthur]

I will assume your wiring is similar to later models. The power is routed directly through the stalk - making it vulnerable to burnout/overload. Relays relieve the load since the load is shifted to the secondary portion of the relay. Relays & wire are cheap whereas the stalk switching is not.

The 2nd connection might be the so-called 4W 'city lights' which many wire as daytime driving lights. Is there a small bulb or another socket in the lamp housing?

Ian

[ossiblue]

Not an expert on this but here's my take.

If you're going with stock wattage bulbs, the existing wiring and switches will handle it but the real advantage of the relay system is to preserve the 37 year old light switch and stalk switch and that, for me, is reason enough to install the upgrade. Odds are, you will never have a problem running without the relays (especially if you don't do much night driving) but if you have a preservationist nature, you will rest more comfortably knowing that you are not stressing your lighting system if the relays are installed.

[2Utes]

The relay upgrade alters the path of the larger currents for the bulbs, taking the turn signal stalk switch and light switch out of that current path. This change should extned the life of these parts and it allows you to use larger gauge wire from the relay to the headlamp reducing lost current due to wire length and small gauge. It is really pretty easy to do and will make your car safer.
Daniel Stern has a very good explanation on his website with general diagrams of how to do the wiring. There are several relay kits available.
I chose to use a 3-relay option that allows both high and low beams to be on at the same time. With the Marchal Ampilux lamp housings (not DOT approved) I have very good to excellent lighting now.

[deshetlr]

The auxillary connector is for the "city lights" option. Do a search. There is a ton of info. Relays are critical if you are using high wattage lamps for any model headlight including the H4. They are optional if you are using standard wattage lamps. You will reduce stress on the headlight switch on the dash either way and that is good. The switch on my '86 failed after 23 years and the failure cost thousands of dollars in repair of the wire harness. That being said I stayed stock. I'll let the owner 23 years from now worry about it.

[geshaghi]

Thanks for all the feedback! Does anyone have a link to Daniel Stern's web site or other diagrams?

[deshetlr]

http://www.danielsternlighting.com/

[HarryD]

The kits offered by Pelican and Marcus Sucro do not work directly with pre-1974 cars. Daniel Stern will send you the parts you need plus a pair of great connectors for the headlamp itself.

A few years ago, I did my own relay upgrade (Daniel Stern helped me out here). Not hard. Plan on an afternnon.

I offer the following thoughts:

1-Wire replacement: In a 30+ year old car, the insulation is brittle and new wires are easier to work with. While a smaller gauge (say 14 or 16) has the necessary ampacity, I choose to use 12 ga for all aspects to keep it simple.

2-Headlamp sockets: As part of the kit I obtained, I got new headlamp sockets. The old ones, like the wires, were brittle and I felt I should have quality sockets to go with my new job.

3-Fuse Panel: The old fuse panel is very brittle. Be careful when pressing on it our it will break (as mine did).

4-With my new relays and wires, the existing sealed beams were definately brighter.

A search will turn up many lengthy discussions and alternative wiring diagrams, but this is my story and I am sticking to it:

http://forums.pelicanparts.com/porsche-911-technical-forum/450640-how-do-i-wire-headlight-relay-post4410268.html?highlight=headlight+relay#post4410268