H4 Headlight Wiring Question

[bigboi]

I have a set of H4 headlights in my car. I had a local shop wire the relay wiring kit up a few years back. Problem is the low beams never did work and I didn't take it back to the shop (don't ask long story).

So as a quick fix I just swapped the wire from the high beam relay to the low beam relay and just drove around with low beams for the last couple years.

Now I am at a point where I would like to get the darn things working. I have done some minor troubleshooting (with my n00b electrical skills) and it appears the low beam relay isn't getting 12v at the wire that should activate the relay to release the power to the low beam wire.

Couple questions...



1)
On these wiring relay kits (i am going to have to trace back the wires and dig) how do they actually work?

2)
Is there a plug and/or a couple wires coming out around the driver side of the fenderwell/radiator support area that plug into the relay wiring?

3)
Does low beam and high beam each have their 12v lead respectively and this is how the lights know to switch from low to high?

4)
Where are these wires accessible in the engine compartment?

5)
There is a few wires that go into what looks to be an electrical board with a few resistors on them. What the heck is this?

I have wiring diagrams for the Camaro and have attached it to this post. It looks like 16T and 16LG are the High/Low leads. I guess I am trying to avoid buying a new wiring relay harness if I don't need to. Any thoughts, suggestions, help would be great.

Brian

[WS6]

Brian this is easy so don't sweat your skills. On the schematic 16T and 16LG refer to two wires that are 16ga(medium in size). One is Tan the other if Light Green. One is 12v to the high beam the other 12v tot he low beam. I'd need to see a schematic of the headlight switch to be able to say which is which.

Now, a relay is nothing but an electric switch. By that I mean it turns on or off by electricity not you pulling a switch or flipping a lever. So, the signal or switch wire for the relays will come from the 16T and 16LG wire. You need one relay each for high and low. So one of those wires will go to one relay.

Both relays will need to get their main power from a main power location. Preferably the alt or the starter. You need at minimum 14ga to power H4 lights correctly. Some run 12ga but 14ga is plenty. One main wire will go to each relay and connect to the normally off terminal. I believe that is 37 not 37a. I always look at the schematic on the side. If it is your typical relay from hella, the center terminal is normal on and is not used.

You'll then run two 14 ga wires from each relay to each headlight out of the 30 terminal.

make sure the relay is grounded to the frame on either the 15 or 16 terminal of the relay. 14ga or even 16ga is fine here. the ground is part of the switch and not the main power.

The headlights will also need their own grounds. One each and they should be 14ga or 12ga depending on what you size you run to the headlights. Grounds must be the same size as power lines.

You'll need fuses on both the main power and signal power lines. 3-5amps on the signal side and 20 on the main power side should be plenty. Be careful if you use the factory harness for signal power as it may be powering something else other than the lights. If that's the case, find out what it is and fuse it properly.

Your harness should be wired very similar to this even if it's an aftermarket one. If it is not, I would consider trashing it and starting over but tell us what you find first as there is another way to do this that's more universal or stand alone but crappy I think. I can supply you with all the wire you need if you want to rewire the whole thing but I am sure quality kits are out there as well.

hope that helps

Oh and to be more clear. The general idea is that when you turn your high beam or low beams on you're actually turning a relay on or off. The relay then allows the respective light to turn on. Your low beams turn off when you turn your high beams on normally. The new way will be the same only it's the relays turning on and off. So yes, they each get their own 12v lead. You can run one 12v lead to both relays as they are not both on as the same time. However, you ever have a wiring problem and you'll lose all lighting. High beams may tick off the other drivers but you'll still get home after dark.

[TnBlkC230WZ]

Brian this is easy so don't sweat your skills. On the schematic 16T and 16LG refer to two wires that are 16ga(medium in size). One is Tan the other if Light Green. One is 12v to the high beam the other 12v tot he low beam. I'd need to see a schematic of the headlight switch to be able to say which is which.

The green and tan wires actually go to the dimmer switch. If you don't have power on one of them, I'd check the dimmer switch. The typical method of hooking up the relays is to turn them on with the original (factory) green and tan head light wiring. These two wires are probably factory and not added by the shop. They are the correct factory colors.

So, make sure you connections at the bulkhead connector are good and make sure the dimmer switch is working. Since you have power on one of them, the headlight switch is working. Make sure the dimmer switch plug is in good condition. Mine was melted on the high beam side.

You have three terminals on the dimmer switch. Power in from the headlight switch, low beam out and high beam out. With a voltmeter, make sure both the green and tan wires get 12 volts at the dimmer switch. Only one will get power at a time.

[mc84_zz4]

For GM cars with the 4 headlight setup, the low beams need to have 2 wire re-oriented in the plug, or else get ONE of these plug-&_play adapters if using the wiring harness.


If you are using the relay harness you only need ONE adapter since there is only 1 plug from the car used to detect low beam or high beam on a 4 lamp car. On a 2 headlight car I cannot speak for sure, but if your lights are not working properly chances are it is the same setup.
If you do not have an aftemarket wiring harness, you will need 2 of these pigtails.

Note: The pigtail adapter has the brown wire ending up in the same position, the other 2 wire can swap locations, and will work for the H4 bulb pin position.
You only need the pigtail adapter or pin swap for the low-beam socket only, the high beam (on a 4 lamp GM) will work without any mods.


Where to get the pigtails & more wiring stuff:
http://www.rallylights.com/SearchRes...CategoryID=581


* OR * just swap the following pins on the stock headlight low-beam sockets in your car:
The green and the brown/tan/pink wire swap locations, the black wire is ground.
(my apologies if the pic is wrong size)

NOTE / DISCLAIMER: you MAY be able to run 2 H4 bulbs without using a wiring harness to power the H4 lamps, but if you have a 4 headlight setup, you REALLY should buy the $25 wiring harness, or your stock headlight switch can overheat and burn out.
The stock wiring on the cars harness has a meager little ground wire. I suggest the $25 wiring harness in any case, since it guarantees 12+ volts to the headlights, and that alone will increase your light on the road.

Another thread w/pics installing a wiring harness for an H4 setup:
http://www.montecarloss.com/communit...276#Post727276

[Fultz1275]

MC84 can you detail your upgrade. I've got a 68 chevelle that I'm wanting to convert all 4 headlights to HID/H4 bulb. If I'm using my factory harness do need 2 of the plug and play adapters you talked about. One for each low beam. Also, what hid ballist kit do you use. I assume you had to buy 2 sets. One for the Lo beams and one for the hi beams. Lastly did you run relays? THanks for any help you can provide.

[mc84_zz4]

MC84 can you detail your upgrade.

I have 4 H4 housings with conventional H4 bulbs, I did install a wiring harness for the H4 setup (summitracing, $30)
I have some glass and steel Bosch units (SBQ46) that spread the light nice and even. I do not have HID bulbs in them.

<< my appologies for the brain dump >>
I was going to try some aftermarket (re-based) HID bulbs, but I have expensive taste. I wan the Bi-Lux version of HID bulbs that have high and low beam, and I don't want to buy the cheap chinese-based bulbs and ripoff-branded stuff.
Also, there is so much discussion about how the re-based HID bulbs produce hotspots in most reflector style headlights, and fly-away glare that blind oncomming traffic.
I think the reflectors with a diffused lens 'could' avoid the hotspots, which I think is more common using the clear lens with stamped reflectors that cause the problems. (?) but I am not going to gamble $200-400 on verifying that.
And the high beams are going to have to stay H4 bulbs anyway, since most HID ballast do not have instant-on, unless the new digital ballasts do that.

You can get some very nice aftermarket H4 housings on ebay, one I recommend is the Autopal brand, and nice replica of the Bosch, Hella design, and there are no mods needed to your buckets.
These are glass lens and steel back, they also have a clear lens (diamond) with the composite reflector style if you prefer those..
You can get some of them with or without 'city lights'.
http://stores.ebay.com/Autopal-Lights
The one required mod is the pigtail/pin swap already mentioned.
You can get 4 of them roughly for $80, add a harness ($30), and then add some extra bulbs($45) and call it good, you would be pretty satisfied with those I am sure.

Here's a pic of the 5 3/4"

Here is their 4x6 as a comparison to my Bosch, they are nearly identical

(see attached headlamp pic on the bottom for comparison)

If you want some top quality, the Hella H4 housings are VERY nice...
Bosch and Hella both make very nice headlights. (Hella +/- $50 each, 200 for all 4, Bosch are a bit more, and harder to find in US)
http://www.rallylights.com/Hella_5.7...Headlamps.aspx

Summit has them w/bulbs..
http://www.summitracing.com/parts/HLA-002850871/
Note, the 'off-road' labeling is the E-code (european spec) and do not have a bulb cover, unlike the diamond/clear lens styles.
Around late 90's many cars changed to clear lenses and began covering the bulb tips to avoid glare. The E-code have a diffused lens, no bulb-tip cover, and do not glare unless you look directly into them... IMO.

You can also 'up' the wattage of the bulbs, however, I cannot encourage this in case officer Bob Speed takes notice of your bright lights...
http://www.rallylights.com/Hella_H4_Bulbs.aspx
I suggest the Xenon+50, they are Xenon gas pressurized and are a LOT brighter, but have a shorter-life penalty.

I also suggest to avoid the colored/tinted bulbs, as a blue filter will reduce about 15% of available light on the road, and are useless on wet roads, (the blue gets absorbed). Now, If you get the tinted bulbs in an 80W, (Xenon XB), that is getting closer to the output of the HID, with the 4,000 Kelvin color, 'true white', same as factory Benz, and BMW...(although these bulbs will also have a shorter lifespan)

The regular H4 bulbs on high beam are pretty aggressive, you project a tunnel of solid light for about 1/3 mile, traffic facing you will not like you.
If you had those 80/100w bulbs, I can almost guarantee you cannot use the high beams, at least not in the city, you could be just asking for a ticket. 100w bulbs are what aircraft landing used to use, BTW.
I ran conventional H4s for years, and they have been pretty rugged, I am going to swap in some Xenon +50 bulbs in, and see how long those last (350-400 hrs), but the conventional are quite bright.
Here's a post on another site, with a few more details, installing the H4 harness.
http://www.montecarloss.com/communit...=690273&page=1

Now, if you have 'more budget than shame', you can get a set of low beams, or the full low/hi beam set from Spitzkraft: ($500, $1,000; respectively)
http://www.spitzkraft.com/catalogue.php?numlow=1
These are TRUE HID projectors with correct D2 HID bulbs, these are the only retro-fit HID I know of that are DOT approved.
Note that the high beam appears as an conventional H1 type, just saying...


HTH