Headlight relay wiring Q

[Guest]

I read the faq relay wiring and I can't figure out which wires I need to hook the relays up to. I've figured the whole wiring setup between the headlights and relays, just not which wires to hook to the current wiring harness, the "switched" wires to terminal 86. I made up a diagram based off of Bill Williams' description and in my diagram it is the purple and blue wires which I do not know where to attach on the car.

On the car's current wiring harness the left headlight has a left brown(ground), middle-top is yellow&black, right is white. The right headlight has the same except the top is yellow&blue. The white wires are joined together before the fuse box into what looks like a 12 or 14g wire while the yellow& blue/black wires go to the fuse box(#9 and 10 I believe).

Here is the relay I'm using, it's a Pico 5590 which is the same as the Hella but much less $.

Should I join the two yellow&blue/black wires together at terminal 86 on the low beam relay and the single white at terminal 86 on the high beam relay? Hacking a wiring harness is not my forte and I don't want to fry anything. The car is a LATE '71 so it's got a 12 fuse panel and should have the same wiring as a '72.

My haynes manual lists a "typical" '02 wiring harness as 6-fuse and the colors are not right, maybe they never updated past the 6-fuse cars? It also lists a Tii with 12-fuse but seems to have some boxes I do not have.

[DavinSF]

. . .and I preferred Susquehanna's page as far as how the info is presented:

http://www.rallylights.com/hella/HeadlampWiring.aspx

There is a typo in their diagram, though. At the top of the diagram they've reversed the high and low beam "To + 12V" connections. This is obvious if you trace them, as the low beam +12V goes into the relay that spits out a current that is listed as high beam and vice-versa.

As far as where to splice your new relays and wires in, all you've gotta do is trace the wire for the high beam and low beam currents respectively from the connector that plugs into the back of the headlight bulb. It's diagrammed as the upper plug on that Susquehanna page, "H4 for Euro applications." I hooked up a test light on each connection and tested the lights to be sure before I cut the wires coming out of them, and I cut, connected, and spliced one at a time to lessen the chance of messing it up.

You basically just cut the L and R low beam, and run the power from the relay to each, then do the same for the high beam. You can then take the original old powered leads that were going to the headlight plugs and use those to connect to the relays. You'll only need to use one side (one high and one low) to make them trip the relays. I checked everything over and over a million times because it's easy to get confused, but as long as you're careful it all works like a charm.

I don't remember the colors of the wires on my car offhand, but I do remember they didn't seem to match up with some of the colors that my manuals listed. Just ignore that and test with a test light to be sure you're dealing with the right wires for high vs. low. It's actually pretty straightforward, and totally worthwhile as I fried a switch before I wired in the relays.

Good luck!

[Gurmail]

Your wiring diagram is correct. However, you're using an incorrect relay.

What you're showing is a closed-type 5-prong single output relay, meaning either '87' or '87a' will work at any one time. They're mutually exclusive. With your current plan, both your left low/high beams will be on all the time, and your right low/high beams will be on when the light switch is activated, at which time your left beams will shut off.

With your current diagram, you'll have the option of using either of the following relay types:

1. open-type 4-prong single out (single '87' terminal) and you connect both your left and right low beam wiring (yellow/black and yellow/blue) to the '87' terminal of your low beam relay and the both high beam wiring (white) to the '87' terminal of the high beam relay.

2. open-type 5-prong dual output (two '87' terminals) and you connect each low beam wiring to each of the '87' terminals, and likewise for the high beam wiring.

Edit:

3. You may use your current relays as open 4-prong single output relays, if you DO NOT connect anything to terminal '87a'. The input to your headlights will come from terminal '87' only. Then you may treat your current relays as that described in "1" above.

[Harv]

I got a relay kit from Danial Stern lighting and the tyco relay he sells has two output terminals so you have one for each headlight. The headlight sockets he sells are ceramic. I just did my car with 10 gauge wiring and I can tell it will work very well when ever I get to drive the car.

10 gauge is way overkill but I had it laying around and it will handle any bulb I throw at it. I was thinking of doing my e30 and I would just use 12 for that.

I would highly recommend Danial Stern's relay kit. It comes with all the special bits you will want.

John

[FunkyLaneO]

the simple answer is that won't work, splice both of your orange wires to terminal 87 and both of your green wires to terminal 87. In this scenario you will not use terminal 87a.

If you did it this way one of your headlights would be on when the light switch is off and one would be off, they would reverse when you switched the light on.

Your battery would not last long with this setup ;-)

The relay contacts are as follows:

30 power to 87,87a

87 switched, normally open (on when switch is on)

87a switched, normally closed (on when switch is off)

85 and 86 are coil (one needs positive and one needs ground to trigger the relay, doesn't matter which)

[Guest]

Your wiring diagram is correct. However, you're using an incorrect relay.

What you're showing is a closed-type 5-prong single output relay, meaning either '87' or '87a' will work at any one time. They're mutually exclusive. With your current plan, both your left low/high beams will be on all the time, and your right low/high beams will be on when the light switch is activated, at which time your left beams will shut off.

Edit:

3. You may use your current relays as open 4-prong single output relays, if you DO NOT connect anything to terminal '87a'. The input to your headlights will come from terminal '87' only. Then you may treat your current relays as that described in "1" above.

That's what I was fearing when looking at the relay diagram. I'll do the 4-pin idea for now.

[FunkyLaneO]

The relay you have will work just fine, in your case SPDT and SPST are interchangeable.

If you want to learn more about relays (they are pretty simple devices) go here: http://www.the12volt.com/relays/relays.asp