Rob Edwards

In my quest to idiot-proof the 928 DIY'er universe, I have today's idiot question. I ordered up 2 pairs of lamp sockets to make some adapters so that I can install Euro H4 lamps without hacking the factory harness.

Dumb Question- if I'm using 80/100 watt H4 lamps, what gauge wire is the minimum acceptable for this service? I would normally just check section 14 of Alan's Wiring Diagram primer: Advanced Wiring Considerations, but tragically it hasn't been published yet...

From the WSM 1990 wiring diagrams, it looks like the factory headlight wires are 1.0 mm2, what gauge does that translate to? Presumeably, if the stock wiring will handle ~8.5 Amps (100W at 12V- west virginia, right?), it ought to be good enough for these adapters ?(assuming I don't make a bunch of cold solder joints at the connectors and increase the resistance)


Here are the sockets in question, just for posterior-ity:

dr bob

Rob--

For that "short" distance, 14ga will be fine. Plus that's about as big as you'll be able to get into those connectors .and. bend around inside the housing.

FWIW, I tried some 80/100 H5's and found that the H5 connector has those tiny pins that don't really carry the current that well; I added little bullet disconnects in the wiring and carried spare H5 sockets with me for easy field replacement. With that consideration, I suggest that you cut off the factory connectors and use just the new H4 socket rather than making the harness adapter. If you really want to get full output from your higher-wattage bulbs, you should add relays to the circuits, powered/fused from the jump-start terminal. You can put the relays in the front of the right wheelhouse near the horns. This will give you full voltage to the lamps, something you will never get with the factory wiring (too small) and the runs to the CE panel and back.

I also hope that plastic socket tehnologies have improved a lot in the poast 20 years. When I used 100/120 H4 lamps in my Lotus, with all the wiring replaced and relayed, I had to go to direct connections and kynar wiring to the bulb. Plastic connector shell and common PVC car wiring insulation couldn't stand the heat. Of course they didn't have the 928 advantage of the air-cooled headlight housings either. Maybe little NACA ducts on the shell, or a corrugated cooling hose up from the bottom...??

Rob Edwards

Sterling-

From Susquehanna Motorsports. The guy on the phone was extremely helpful and there's a lot of useful info on their website. They stock all sorts of Hella relays and the reasoning for their use. Per Dr. Bob's suggestion, I think I need to investigate how to wire these up properly with a relay.

EDIT: They have a writeup on the very subject:

http://www.rallylights.com/useful_in...amp_wiring.htm


Here's the socket listing:

http://www.rallylights.com/hella/Connectors.asp

Alan

Porsche 1.0 wiring is approximately 16 AWG (or smaller) though if you can fit 14AWG thats good too.
You can clearly see here one of the disadvantages of the H5 style connector - the blade size & even wire crimp capacity is very limited compared to the quick disconnect style used for the H4's. Unfortunately that will limit your wire size in all likelihood to 16AWG - but that's no worse than the stock ~10' of wiring back to the relay.

The extra connections actually may be the worst part - make sure they mate well are taped together and I'd spray a contact protectant on too.

Overall while I understand the rationale - its better electrically to just install the H4 connector directly - and as you have no doubt found out its a lot cheaper to just buy a whole new H5 female socket connector for later reuse than to buy those H5 plug parts...

For the best possible lighting results you'd need relays (4) for the headlights - fed from the alternator direct or jump post - ideally with at least 12AWG wiring for the feeders These need to be fused individually too - but you can gain quite a bit of brightness this way. Susquehanna Motorsports diagram shows only 2 relays shared across both sides - but since Porsche goes to the trouble of giving you more redundancy (less risk you lose both lights at the same time) you should maintain this (especially since adding more relays always add some additional failure risk).

I did find the detail required in:
Section 17 MORE ADVANCED WIRING CONSIDERATIONS (note that I have added bunch of sections...)
Table 9 Porsche Wire Size Notation, Current Capacity & ~Equivalents:

...However you are correct its still not published yet - I keep trying to work on it to finish it up - but my day job, family and fixing my car seem to keep getting in the way.Alan

Rob Edwards

Alan-

Thanks for the info, much appreciated. After blowing $30 on these connectors, I was looking at the pin connectors in the H5 socket and thinking, damn, those things are small. I think you and Bob are right, the H4 connector needs to go straight to the harness.

4 relays? 1 each for high-beam and low beam on each side? Got a napkin diagram as to how that would be wired? I would take the supply voltage with some ring terminals on the jump post, but after that I'm not sure how/where to install the components.

BTW, just good natured ribbing about your wiring primer, I understand how those pesky kids and day jobs get in the way of the hobbies. I will look forward to buying a copy whenever you get 'er done.

Alan

Rob - like their diagram but just do it for each side individually. In fact doing this you could simply wire a 12AWG feeder to each headlight area and install the relays there (either under the headlight or possibly even in the pods). You should also run new independent grounds to the front ground points connected with ring terminals - they are quite conveniently located for this.

This will also give you a good reason to still use the new H5 male connectors - without the current load to worry about these are an excellent way to connect to the existing headlight wiring (without modifications) to get the coil feeders you need.

You can get standard Bosch style SPST relays but I'd use the mini SPST size & connectors (http://order.waytekwire.com/IMAGES/M...og/220_060.PDF)
if you decide to install into the pods. The pod covers only take a minute to get off so this is a convenient and yet well hidden location.

However you will also need a single fuse per side to protect the feeder wiring to the pods. Rather than adding a fuse per filament - 1 fuse per side seems adequate to me... and you can place this at the jump post to protect the feeder and everything downstream on that side. Inline sealed ATX fuseholder versions with 10/12 AWG should be fine.

If you wanted a fuse per filament (4 total) you'd have to put these near the relays (and still protect the feeder) OR wire 2 fuse protected feeders to each relay each side... kind of overkill.

For 100W 10A fusing is fine for the stock wiring but 15A might be better for this relay upgraded wiring (your current spike on turn on will now be much bigger)

You need to ensure the power & ground feeder wires to the pods are very flexible (large strand count) and with good thick & flexible insulation since they need to flex with the pod rotation.

Alan

Ed Scherer

FWIW, I left my 9004/H5 sockets in when I installed my H4 HIDs. Just wired the two sockets in parallel. That way, should it ever be necessary (unlikely), I can revert to the old headlights if I want to.

Alan

Ed - yes good idea - I actually considered this when fitting my H4's but decided I'm never going back... (or selling!).

In Rob's case fiting both H5 & H4 connectors in parallel allows:

1) easy reversion to H5's at a later date (swap H4's & relays etc to another 928?)

2) Easy plug & play install as noted above*

3) Bypass of the new relays and reversion to ROW stock configuration via H4 connector as a back-up plan

*Can get the same benefits in 2) & 3) by just installing an H4 connector in place of the H5 connector - not a bad back-up plan...?

Alan