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Draft Headlight H4 Relay Article -- comments, critique?

Here is the draft of a tech article relating to the procedure I used to install headlight relays for the H4s on my 1969 911. I hope this helps and comments/improvements are appreciated.

Rich

----------------------

Installation of Relays for H4 Headlights

Background:

The installation of high-powered H4 headlights, fog lights and rally lights will often overload the headlight switch wiring circuit. Given that the headlight switch is quite expensive, the factory wiring was never designed to carry this much current and that overloading the circuit could prove a hazard, the use of relays is a good idea.

A relay is merely a remote controlled switch. The purpose of the following procedure is to create a new power supply from the battery directly to the headlights such that the existing wiring will serve merely will operate the relay (i.e. the switch), which is a very low power operation. When you turn on your headlight switch, it will (effectively) reach out and throw the new switch in the headlight bucket – the current to light the bulb will be coming directly from the battery. Similarly, when you turn on the high beams, it will reach out and throw the high beam switch in the headlight bucket – the current to light the high beam is coming directly from the battery.

I used two relays for each circuit because I wanted to minimize the rewiring and hide everything inside the headlight bucket assembly, but you could use a single relay for each of the high beam circuit and the low beam circuit.

Parts Needed
· 4 relays (Hella Part No. )
· 10 feet of 12 gauge red wire (new power supply)
· 2 feet of 12 gauge black wire (new grounds)
· 2 feet of 12 gauge white wire (new low beam connection from relay to headlight)
· 2 feet of 12 gauge yellow wire (new high beam connection from relay to headlight)
· 2 in-line fusible links and 10 amp fuses
· 20 female blade connectors (for connections to headlight and relays, preferably the fully insulated style)
· 2 butt splice connectors (to join fusible link to new power wire)
· 2 small round crimp-on terminal connectors (for ground wires)
· 1 large round crimp-on terminal connector (to the battery)
· 6 sheet metal screws and washers
· electrical tape

Tools Required:
· Wire cutters
· Wire stripper
· Drill
· Screwdriver

PROCEDURE

NOTE: Please refer to the wiring diagram attached as Figure 1 (SEE BELOW). On my car (a 1969 911E) the yellow wire was for the high beams and the white wire was for the low beams. Check at your fusebox and see if it is the same for your car – it may vary but all the rest of the description is based on this color scheme. Just adapt to your car’s colors.

A. At The Workbench:

1. Make up two white wires and two yellow wires (each about 9 inches long) with a female blade connector on each end. These will be the new wires to the headlight three-prong connector from the relays.

2. Take both of the fusible links and stick one end of each into the large round terminal connector that will attach to the battery positive terminal. The other side of each fuse will go to the red power wire for each headlight assembly. (Note: some people put the fuses in the headlight bucket itself, but I wanted to be able to get to them without pulling the headlight so I wired them up inside the trunk so I could get to them easier.)

3. Make up two “Y”-shaped ground wire assemblies. Each ground wire assembly consists of two black wires (each about 4 inches long) with a female blade connector on one end. The free ends of each wire should be crimped together in the round terminal that will be screwed to the bodywork as the ground.

4. Connect the ground wires to the #86 terminals on the relays (you should have two assemblies each with two relays). With respect to each assembly, connect a yellow wire (that you made in step 1 above) to #85 on one relay and a white wire (that you made in step 1 above) to #85 of the other relay.

B. At the Car:

1. Remove the headlight assemblies and disconnect the wires. If your wires are still in a single three-prong connector, remove the wires from this plastic clip saving the connectors (if possible).

2. Drill a hole in the bodywork from inside the trunk on each side close (but not too close) to the point where the existing wiring harness passes through the bodywork.

3. Drill a hole in the headlight bucket (again, close to the point where the existing wires enter the headlight bucket. (Smart people will put a little rubber grommet at each point where the wire passes through the bodywork and seal it with silicone sealant to protect against water leaking in. I’ll do this soon.)

4. Run a wire from each the headlight bucket (leave yourself some extra) through the holes you just drilled and run it along the existing wiring harness (electrical tape to secure it) until it reaches the fusible link. Connect the wire from each headlight bucket to one fusible link with a butt splice connector.

5. Leaving a little extra coming through the bodywork (you don’t want the wire tight), cut the red wire as appropriate to attach to the relay and cut a small length of red wire sufficient to jump from one relay to the other once installed. Crimp the bare end of the main power wire and one end of the jumper into a single female blade connector. Put another female blade connector on the other end of the jumper wire. Connect these wires to #87 on the relays for each headlight assembly.

6. Hook up the existing wires to the #30 position on relays. The yellow wire to the one you have a yellow wire already on (this is the low beam relay) and the white wire to the one with the white wire already attached (high beam relay).

7. Mount the relays using a sheet metal screw inside the back of the headlight bucket towards the bottom so as to make the maximum space for the headlight.

8. Connect the wires to the three prongs on the back of the headlight as shown in the wiring diagram (brown at 9 o’clock, yellow at 12 o’clock and white at 3 o’clock) and fit the headlight assemblies into place gingerly to ensure that there is no interference with the wiring or relays.

9. Hook up the large loop to the positive terminal of the battery.
10. Put the fuses in the fuse holders and turn on the headlights.




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Old 10-15-2002, 09:54 AM
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These look very good at first blush. I just received the relay kit and am looking very forward to putting the high beam fuse back in again!

I'll probably try to get the kit in today (Wed) and will give you the benefit of my experiences.

Thanks for doing this,
John
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Old 10-15-2002, 10:11 AM
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Hi:
Small critique...hopefully RoninLB ( sp?) will chime in...
1.) I would not want to place the relays inside the headlight bucket, where it is both very inaccessable ( need to remove the headlight) , and also is a place where moisture and water accumulate. The relays ( with extra lengths of wire) can be placed almost anywhere...why not inside the trunk?
2.) The "control" circuit ( as opposed to the "power" circuit) is simply an electromagnet that closes the the high-amp "power" circuit contacts ( i.e...the wires from the exisiting fuse box). The control circuit is very , very, low on amp draw..therefore, why the high value 10A fuses? Don't know how much less the control circuit draws, but it may be on the order of 1 amp or less. Provide a closer match to this draw in amp size.
3.) If you use crimp connectors, use ones like those made by ANCOR, a marine grade that encapsulates some glue in the splice/crimp connector. That way, when you apply heat to shrink the ends, it also melts the glue and makes a tighter, more water-proof seal. There are other connectors that also have a dab of solder in the crimp joint , which makes it just that much better, by making a soldered joint.

Otherwise, a fine effort including good graphics !

--- Wil Ferch
Old 10-15-2002, 11:13 AM
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Oh...
one more thing....

Most Porsches use yellow wire for low beams ...and white wire for high beams...never heard of it being other way 'round...but I never looked at 911's of your vintage. I know you said to check colors, but the "most seen" convention I've ever come across is just the opposite of your desription. Maybe a "caution" note to this effect ??

---Wil Ferch
Old 10-15-2002, 11:18 AM
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Rich911E--

Wonderful job!

Since I'm somewhat 'electrically-challenged' I'll let others comment on the technical aspects.

Question - why not have the relays mounted close to the fuse box? Would seem to minimize the chance of moisture at an electrical connection.

My other suggestion would be to include step by step pictures, both of the pieces being made and their installation.

Super effort - thanks.

FYI, I installed the relay kit provided by msucro which worked very well and had excellent installation instructions included.
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Last edited by steve911; 10-15-2002 at 11:33 AM..
Old 10-15-2002, 11:21 AM
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great effort Rich, thanks...
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Old 10-15-2002, 11:49 AM
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I was looking at doing this, but I wanted to go the factory replay plug route (set into the existing fuse panel). maybe an addendum on factory relay part numbers, diagrams, etc?

Thanks!

Chuck
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Old 10-15-2002, 12:30 PM
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Rich,

A great first draft! My suggestion would be to substitute 'H1/H4' for H4 in your title, since it applies equally to any '65 thru '89 car's wiring, and to the entire familiy of Bosch Halogen headlamp assemblies! The use of H4 narrows your target audience unnecessarily.

A couple of corrections to your circuit diagram, which is quite good, esthetically and visually:

1. By DIN/German convention, Terminal #85 of a relay is the ground connection for the coil.

2. You have Terminals #30 and #85 reversed at the relay ... the control signal from the fuse block should go to the relay coil ... actually terminal #86!

3. As Wil pointed out, white wire is for high-beams in most cars, although '74 thru '83 color codes were an odd combination of Yellow & Green/Yellow for low beams, and Blue & Blue/White for high beams ... from the fuse box.
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Last edited by Early_S_Man; 10-15-2002 at 01:41 PM..
Old 10-15-2002, 12:36 PM
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Cool

this thread is full of good info..sometimes not good enough for everyone..I agree with Wil on where to position relays..and when Wil refered to the control circuit fuse, the relay draws about 600mil amp..and using marine grade parts is a home run, especially marine grade wires..Anchor is the routine marine supplier to many marine stores/great product..and I do use solder for all connections...there is a Bosch high amp bulb socket that I use..stock sockets will either melt or cause a fire when using real high watt bulbs, like 130/100w Narva bulbs..which is doable on a 911, because headlights are relatively low.. a lot of this is personal prefence..my install is what is necessary for my comfort level, which is bullet proff/but may not be cost efficent..but that's my problem.............................Ron
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Old 10-15-2002, 01:26 PM
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Rich, article in last month's pano on headligh relay installation recommended using 10 gauge or even 8 gauge wire. I am not an engineer so I cannot comment intelligently; however, I generally always go very conserative. I am using 8 gauge in my relay install, which is probable way overkill. Are there downsides to this?

Chuck
Old 10-15-2002, 01:40 PM
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In addition to the previous suggestions I would add that Ancor marine grade wire which is not only tinned(a coat of tin/solder has been deposited over the full length of each strand for corrosion resistance) but also type 3 strained(more strands of copper therefore more cu. and more flexible) is a perfect match for the glue/shrink wrapped fittings mentioned by Will. This AWG wire is also 6-12% larger than SAE gauge and thus better current carrying ability. This wire is available in mini spools(8', 12', 18' or 25') in red, black, green, yellow, blue,orange, brown, gray or purple

FYI current loss in 12vdc circuits is a huge issue. For a 10 amp circuit in 12AWG wire there is a 3% voltage drop in ~16' round trip.
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Old 10-15-2002, 01:40 PM
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Chuck,

The primary reason the Pano article used larger gauge wire is because the article was specifically targeted at 356 owners and 6-Volt systems ... or was that the Excellence article? Because 6-Volt systems are even more critical in regard to Voltage drops, wiring one size larger than 12-Volt circuits is typically used.

In any case, 12 gauge wire is adequate for 130 Watt bulbs on a single circuit, which will only see slightly less than 10 Amps! If the ground wire in the headlamp bucket will ever see the load from both bulbs simultaneously, then it needs to be larger, such as 10 gauge or 8 gauge.

One final note ... you don't even have to use a three-prong socket at the headlamp, as long as a pinout diagram is taped to the wire bundle or inside the bucket! You DON'T want to use insulated Faston connectors, as they aren't rated for temps above 105°C that the bulb and bucket environment will see at night in use! Like Ron, I prefer soldered connections!
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Old 10-15-2002, 02:18 PM
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Holy Cow !!
Yep...Early_S_Man saw something very important. Terminals 85 and 86 should be shown "opposite" of one another....same with 87 and 30. Meaning? 87 and 30 are the main contact points....85 and 86 power the control circuit ( "electromagnet"). Both pairs are bi-directional ( example...either 86 or 85 can go to ground, but DIN convention may only show 86 to ground , I guess).

Upshot...the wiring diagram is technically flawed as shown and must be corrected for proper "pairing" of the numbers...or the system won't work or ( worse) might fry!

Good catch "S" man !!!


---Wil Ferch
Old 10-16-2002, 07:09 AM
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Why not run one relay for each Hi and low beam? Using only two relays?

I have one Bosch (round style) relay for each hi and low circuit. I used the factory round mountings and mounted these in the fuse panel, as I had two relay holes available.

This way, I was able to essentialy use the factory wiring and fuses while incoporating a relay with better power - negating the factory light switch as the failure point.

I imagine the response is because of the issues with higher wattage bulbs will require larger wiring.

Curious - thanks.
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Old 10-16-2002, 09:39 AM
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Nick:
Your method has merit, and can be done that way. I used the Marcus Sucro kit which also used 2 relays. Later, out of anal-retentiveness...i swapped out the original relay "cubes" with Bosch units rated at 50A instead of the normal cube 30-40 amp rating. I think they have silver contact point, too. Don't need the rating, but the service life might be improved. Here are some possible relay part numbers ( cube style):
- Bosch 0.332.019.110
-Bosch 0.332.019.150
-Porsche 911.615.103.00
-Porsche 944.615.116.00

yeah...using two... wired the way I did them according to the kit instructions... wouldn't lend to super-high watt bulbs, since you're still using the stock fuses and downstream wiring to the headlights.


---Wil Ferch
Old 10-16-2002, 03:39 PM
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[QUOTE]Originally posted by Wil Ferch
[B. Later, out of anal-retentiveness...

Yeah, I know about that anal-retentiveness..I had a BRIGHT idea to wire the high beam and low beam filiments together when I triggered the high selection...well, they gave great light..and the road was lit up like daylight...BUT, in about an hour of useage the bulb internal ground went kaput..used a diode/75 amp relays/big wires..Dan Stern Lighting said there were exotic bulbs around to serve my purpose/never followed thru on it.........Ron
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Old 10-16-2002, 04:14 PM
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