Make your own relay harness, schematic, parts inside

Slithering_Joe · 01-21-2008, 06:22 AM

It is simple to build your own Headlamp Relay Harness. Below is specifc to a TJ but can be applied to just about any car that utilizes only a switch to control the headlamps. A relay harness constructed with short length heavy gauge wiring will enable one to get the most light output from their current headlamps whether they are sealed beam, H4 conversions or higher wattage bulbs.
You will not have to cut any factory wires. You will use one of the existing headlamp connectors to trigger the relays. The other headlamp connector will be taped up and shoved away. Many automotive parts stores carry replacement headlamp connectors. Get the ones that will work for you application.

Headlamp Relay Harness Schematic:

The itemized parts below can be found at www.rallylights.com

(2) Hella Waterproof/Weatherproof Skirted Relays (**):
(Item #HL87411, SPDT, Resistor)

(2) Hella Waterproof/Weatherproof Relay Base(**):
(Item #HL87173, 5-Wire)

(**) To lower the cost, you can use standard Hella relays. All Hella relays are designed to be used in an underhood automotive envirionment but it is recommended that waterproof/weatherproof relays are to be used if they are excessively exposed to mud and water.

Below are available at any Pep Boys, Autozone, Advance Auto, or a similar auto parts store)

(2) Mini-Fuse Relay Holders, 12GA:

12GA Wiring
16GA Wiring
(3) Male Quick Disconnect terminals (16-18GA, 0.25-inch)
(2) 20A Mini-Fuses
(2) H4 Headlamp Replacement Connectors (Female) (HL28001 H4 Replacement Female Socket, 10 gauge)

ZX14Rider · 01-21-2008, 06:55 AM

Saved in favorites for future use..

Thanks for posting..

Zoom By You · 01-24-2008, 04:15 PM

Hey Slithering Joe, thanks for posting the schematic; I already have most everything I need to make it, just have to pickup two H4 Headlamp Replacement Connectors, which my local guy has in stock. One question, on the relay, the 87a terminal is left blank, correct?

Slithering_Joe · 01-24-2008, 04:28 PM

Quote:

Originally Posted by Zoom By You

Hey Slithering Joe, thanks for posting the schematic; I already have most everything I need to make it, just have to pickup two H4 Headlamp Replacement Connectors, which my local guy has in stock. One question, on the relay, the 87a terminal is left blank, correct?

Yes, if you locate a relay that has the 87 and 87a terminals, leave the 87a blank. But, if you can locate a dual 87 terminal relay, it will make the installation a little easier. You can dedicate each 87 terminal to their own lamp. The additional 87 terminal is in the same position as the 87a terminal. The relay internals are different.

See below:
87-87a Relay pin configuration

Dual 87 Relay pin configuration (preferred for easy installation)

(Photos courtesy of www.rallylights.com)

Zoom By You · 02-02-2008, 11:19 PM

OK, this was a great upgrade, which didn't cost a lot of money. I used Slithering Joe's schematic and constructed the harness outside the Jeep, then installed it. It worked like a charm and improved the efficiency of my Fatboy's significantly over the stock wiring; I mean you can really see the difference! Joe was very helpful and I appreciate his assistance with this project....

Slithering_Joe · 02-03-2008, 07:44 AM

I was messing around with an amp meter and I came up with these total current measurements:

Engine Off, Low-beams, 2 X 80W:
12.59A
Engine On, Low-beams, 2 X 80W:
13.75A

Engine Off, High-beams, 2 X 100W:
13.38A
Engine On, High-beams, 2 X 100W:
14.48A

Without a relay harness, that would be a lot of current making its rounds through the headlamp switch and dimmer switch. That current would have to travel from the battery in the engine compartment, to the inside of the vehicle, through the headlamps switch, through the high-beam/low-beam dimmer switch, and then back outside again all the way to the headlamps. With a relay harness, the current only needs to travel from the battery, through the relay, to the headlamps all within the engine compartment.

TheMike · 02-12-2008, 06:09 AM

Nicely done! I appreciate your work here. I also have most of the supplies to do this myself but over the last couple of days I have been researching commercially available harnesses. Your schematic is exactly what I needed to see to put me over the edge to just do it myself. This way I get better wires and I know exactly what's there!

Again, thanks!! Mike

Slithering_Joe · 02-12-2008, 06:22 AM

By request, for using a 87-87 (dual 87 terminal) relays. Not much of a difference. Two less spliced wires.

ISO 87-87 Terminal Relay:

(Photo courtesy of www.rallylights.com)

**ImaginaryFriend** · 02-17-2008, 01:45 PM

I've been wanting to do this for some time. I pretty much had it figured out in my head, but the schematics definitely help. thanks!

Questions...
I noticed it says that "a typical H4 connector will not fit factory harness headlamp connector". I thought these aftermarket headlamps/lamp housings like the IPF plugged right into the factory harness? Are they not standard H4? Or do they come with a little adapter? I wouldn't mind doing more of a "plug" than the male connectors, what then could be used?

And doesn't that mean that the new H4 female connectors (headlamps) may not match the lamp housings?

Slithering_Joe · 02-17-2008, 08:38 PM

Quote:

Originally Posted by symbiont7

... I thought these aftermarket headlamps/lamp housings like the IPF plugged right into the factory harness? Are they not standard H4? Or do they come with a little adapter? I wouldn't mind doing more of a "plug" than the male connectors, what then could be used?

Look at the schematic again. I do not think you are reading/understanding it thoroughly. The vertical dashed line seperates the original factory components from the relay harness you will be making. The relay harness you make plugs into the factory headlamp connector. The other factory headlamp connector is disconnected, taped up and not used. The original headlamp connector is used as an input to the relays in the relay harness.
The original factory connector housing may not fit inside a mating connector housing that you may find in a store. This is either due to that the factory connector housing outer dimensions are too large or that the mating housing inner dimensions are too small. I just used male quick-disconnect spades and pushed them into the correct female pins of the factory headlamp connector.
Another way to describe this: The original factory connector has female pins but the connector housing is male. The connector that would mate with this has male pins but the housing is female. There can be a case that the two housings, not the pins, may not fit.

Quote:

Originally Posted by symbiont7

...
And doesn't that mean that the new H4 female connectors (headlamps) may not match the lamp housings?

No. There is nothing to inhibit the connectors from the headlamps.

**ImaginaryFriend** · 02-17-2008, 09:42 PM

Quote:

Originally Posted by Slithering_Joe

Look at the schematic again. I do not think you are reading/understanding it thoroughly. The vertical dashed line seperates the original factory components from the relay harness you will be making. The relay harness you make plugs into the factory headlamp connector. The other factory headlamp connector is disconnected, taped up and not used. The original headlamp connector is used as an input to the relays in the relay harness.
The original factory connector housing may not fit inside a mating connector housing that you may find in a store. This is either due to that the factory connector housing outer dimensions are too large or that the mating housing inner dimensions are too small. I just used male quick-disconnect spades and pushed them into the correct female pins of the factory headlamp connector.
Another way to describe this: The original factory connector has female pins but the connector housing is male. The connector that would mate with this has male pins but the housing is female. There can be a case that the two housings, not the pins, may not fit.

No. There is nothing to inhibit the connectors from the headlamps.

I fully understand the schematic and the dashed lines, I just am not familiar with the connectors used and any "standards" present. So the issue is the housing tolerances and not the pin layout.

What I was confused on (since I haven't looked at the housings/pins, stock or H4) was the comment about the connectors not fitting. I thought it was because of pin layout, not housing tolerances. Therefore following my incorrect train of thought, if it did indeed have a different pin lay-out (H4), why would they work on the lamps (OEM) but not the factory connectors (OEM), both of which having the same pin lay-outs. See my confusion?

Hopefully I'm making sense!
So in other words, an H4 has the same pin lay-out as the factory sealed bulbs and it's a lack of "standard" housings causing the issues.

Your further explanation helped a ton! Thanks again.

Slithering_Joe · 02-17-2008, 10:05 PM

Quote:

Originally Posted by symbiont7

I fully understand the schematic and the dashed lines, I just am not familiar with the connectors used and any "standards" present. So the issue is the housing tolerances and not the pin layout.

What I was confused on (since I haven't looked at the housings/pins, stock or H4) was the comment about the connectors not fitting. I thought it was because of pin layout, not housing tolerances. Therefore following my incorrect train of thought, if it did indeed have a different pin lay-out (H4), why would they work on the lamps (OEM) but not the factory connectors (OEM), both of which having the same pin lay-outs. See my confusion?

Hopefully I'm making sense!
So in other words, an H4 has the same pin lay-out as the factory sealed bulbs and it's a lack of "standard" housings causing the issues.

Your further explanation helped a ton! Thanks again.

H4 and sealed beam have the same pin layout. That is why a female-pin H4 connector works on a male-pin seal beam lamp. From what I gather, it looks like the factory Chrysler/Jeep sealed beam headlamp connector is a little too thick to fit into the complement side of an H4 connector. I cannot find a connector that will fit the factory sealed beam connector housing. The complement H4 connector housing is tempting to use since is has the same basic shape and pin layout. Yet, it is so close but just slightly too large.

To add a little confusion, some H4 connectors have different High-Beam/Low-Beam/Ground pin designations.

jshaab2 · 03-20-2008, 03:19 PM

nice..10char

Slithering_Joe · 05-29-2008, 07:37 AM

Quote:

Originally Posted by thedirt

Just ran out and took a look at my headlight connectors, and on my 2005 (the passenger side, at least) had three wires

..[1]
[2][3]

1 -- White with green stripe
2 -- Black
3 -- Green with white stripe

Granted, my connectors are covered with crap (I'll clean them off when I install this), but I'm not sure how those translate to the colors used in the diagram above.

Anyone know?

Here ya go, from the 2005 TJ Service manual:

Main Color/Stripe Color: Description
White/Lt Green: Headlamp Low Beam (+)
Lt Green/White: Headlamp High Beam (+)
Black: Headlamp ground (-)

From the looks of the wiring diagram, the Right Headlamp is feed from a daisy-chain off of the Left Headlamp.

gofish38701 · 06-02-2008, 03:26 PM

I've had this harness installed in my Jeep for about two weeks now. I am still running factory headlights but will upgrade as cash becomes available. The improvement to the OEM lights was quite noticeable. I do have some quirky thing going on though...

Twice now the high beams have stayed on after dimming and/or turning off the headlight switch. Nothing that I do makes the high beams turn off. Both times, they turned off by themselves after a couple of minutes. I have looked at the relays and nothing is jumping. I have no reason to believe that my dimmer switch is bad because while in this condition, the low beams will switch off and on. I am drawing power from the terminal side of the starter solenoid. Could this have anything to do with it?

Thoughts or ideas?