headlight wiring to H4s (with pics)

[garment]

Hi - I'm replacing headlights with H4s on my '83 911SC. When I went to replace my headlamps with H4s, i found out that there is no wiring harness for the new H4 bulb. No big deal to splice one in, but I don't know which bulb connector to wire to the original harness wires (blue/white, brown, and yellow for the right headlight, and green/yellow, brown, and blue for the left) to give proper high and low-beam performance. Can you advise? You can see the connector I will be splicing to the original wiring attached. In case it's not obvious in the pics, if you are looking at the receptacle side of the new connector, colors are as follows:

Black | | Red
__
Green

Help get this Pelican back on the road! Thanks, Pelicans!

[RSTarga]

Yellow is low beam, white or blue are high beam, brown is ground
Make sure and put in relays too

[heimtun]

Color me confused. H4s should be plug and play with original wiring. In other words, H4 connectors should look and act just like old sealed beam connectors.

[garment]

Seems like the harness was snipped off and the bulb wired directly to the bulb. Not my suggestion, but seems logical see my earlier thread here. And hat tip to faverymi!

Originally Posted by heimtun

Color me confused. H4s should be plug and play with original wiring. In other words, H4 connectors should look and act just like old sealed beam connectors.

[garment]

Awesome pic, thanks! Did you run across this issue with your car?

Originally Posted by RSTarga

Yellow is low beam, white or blue are high beam, brown is ground
Make sure and put in relays too

[heimtun]

Originally Posted by garment

Seems like the harness was snipped off and the bulb wired directly to the bulb. Not my suggestion, but seems logical see my earlier thread here. And hat tip to faverymi!

Gotcha.

[porwolf]

Originally Posted by garment

Awesome pic, thanks! Did you run across this issue with your car?

Just to be sure it helps to check voltages on the 3 wires at the high and low beam switch settings before you splice or solder on the new connectors. Just in case the PO screwed up wiring in other places also.

[garment]

Hadn't thought of that - just checked, here's what I'm getting on the right side, all with ignition on but car not running:

Blue (Hi Beam) - 4v on low, 11.6v on hi
Yellow (Lo Beam) - 11.8v on low, 11.4v on hi.

Any thoughts?

Originally Posted by porwolf

Just to be sure it helps to check voltages on the 3 wires at the high and low beam switch settings before you splice or solder on the new connectors. Just in case the PO screwed up wiring in other places also.

[porwolf]

Originally Posted by garment

Hadn't thought of that - just checked, here's what I'm getting on the right side, all with ignition on but car not running:

Blue (Hi Beam) - 4v on low, 11.6v on hi
Yellow (Lo Beam) - 11.8v on low, 11.4v on hi.

Any thoughts?

Looks OK so far except for the 11.4V at the yellow wire "on high". That should not have voltage on it unless the steering wheel dimmer paddle is moved into the forward position. The 4V on low at the blue wire (high beam) seems to be just spurious voltage at the open circuit there.

Whether the voltages at the various settings really mean that also sufficient current is available it would help to just connect any 12V light bulb between ground and the blue and yellow wires at the various switch settings.

Do plan to install relays though. Now is a good time. It would make the light bulb current flow so much simpler and safer for all the switches involved. It would have the current flow going directly from the battery, through the relays, to the light bulbs without passing through the various switches. .

[ParkerFE]

I had always though that you need to run bigger 12 gauge wire to a relay and then to the H4 connector to get the best light output from an H4 upgrade?

[porwolf]

Originally Posted by ParkerFE

I had always though that you need to run bigger 12 gauge wire to a relay and then to the H4 connector to get the best light output from an H4 upgrade?

In my H4 relay setup I did run AWG12 gauge wires from the battery to the relays. But then connected the factory head light wires to the relay outputs. I think the factory wiring to the head light bulbs is Ok for 50/55W light bulbs. Those H4' bulbs together with the relays get plenty of voltage at the running currents. Only if you want to install 80/110W light bulbs could you get better voltage with bigger than factory wires (including ground connections) at the bulbs themselves. But that would heat up the light fixtures beyond designed temperatures also. And the 3-prong socket should be ceramic instead of plastic. The light output is very sensitive to slight variations in bulb voltage.

[garment]

Yes, I had the paddle forward and yes, relays are on tap. Speaking of which, heading to Sears now to get a tap and die set, the welded-in nut at the bottom of the bucket is not cooperating with the new screw at the bottom of the new headlight assembly. Thanks so much for the responses!!

Quote de garment

Hadn't thought of that - just checked, here's what I'm getting on the right side, all with ignition on but car not running:



Blue (Hi Beam) - 4v on low, 11.6v on hi

Yellow (Lo Beam) - 11.8v on low, 11.4v on hi.



Any thoughts?

Looks OK so far except for the 11.4V at the yellow wire "on high". That should not have voltage on it unless the steering wheel dimmer paddle is moved into the forward position. The 4V on low at the blue wire (high beam) seems to be just spurious voltage at the open circuit there.



Whether the voltages at the various settings really mean that also sufficient current is available it would help to just connect any 12V light bulb between ground and the blue and yellow wires at the various switch settings.



Do plan to install relays though. Now is a good time. It would make the light bulb current flow so much simpler and safer for all the switches involved. It would have the current flow going directly from the battery, through the relays, to the light bulbs without passing through the various switches. .

[porwolf]

Originally Posted by garment

Yes, I had the paddle forward and yes, relays are on tap. Speaking of which, heading to Sears now to get a tap and die set, the welded-in nut at the bottom of the bucket is not cooperating with the new screw at the bottom of the new headlight assembly. Thanks so much for the responses!!

Oh, and when you finally install the H4's assemblies make sure the the headlight tab at the bottom of the fender bucket is bent to have the mounting screw thread pointing downwards as much as possible. When you use the Phillips screw driver its shaft should be touching the SC bumper so that it is almost impossible to turn the screw driver. This way the H4 ring is pulled down enough to engage positively with the retainer tab on top of the headlight bucket. Ask me how I know!

[garment]

What size is the screw at the bottom of the trim ring? I'm at The Depot and the selection of taps is weak, looks like back over to sears for a whole set.

Quote de garment

Yes, I had the paddle forward and yes, relays are on tap. Speaking of which, heading to Sears now to get a tap and die set, the welded-in nut at the bottom of the bucket is not cooperating with the new screw at the bottom of the new headlight assembly. Thanks so much for the responses!!

Oh, and when you finally install the H4's assemblies make sure the the headlight tab at the bottom of the fender bucket is bent to have the mounting screw thread pointing downwards as much as possible. When you use the Phillips screw driver its shaft should be touching the SC bumper so that it is almost impossible to turn the screw driver. This way the H4 ring is pulled down enough to engage positively with the retainer tab on top of the headlight bucket. Ask me how I know!