Lets start off and show how it really looks like under the hood:
Imagine that we connect the HID ballast directly to where
the low beam halogen bulb is connected. Some vehicles might be are able
to power up HID systems normally without problems at install time. Most
probably, it will not last long. The inrush load can be up to max 13 amps
per ballast, compared to 7amps inrush when using halogen. The factory design
parameters for headlight curcuit is 7 amps inrush and 4.5 amps continous
load. So over time, connectors, multifunction switch, headlight switch,
wiring and fuse holders will slowly degrade, beacuse of heat buildup. These
components are very time consuming to troubleshoot becuse they are usully
well hidden behind dashboards and other wiring looms. Parts easily reaches
several hundered dollars. Add 8h labour to that and it becomes obvious
that a $50 wiring harness is a cheap insurance.
During normal HID operation, you use only 42 watts (35W to run the bulb plus 7W in heat losses in ballast) instead of the 55 watts that the halogen bulb uses, which is less, but, during HID cold startup, and for the first several seconds during warmup, the HID system can draw up to triple the normal operating power to run the ignitor circuit during that time. As the bulb warms up, the current draw tapers down to the normal running level. By powering the ballast through a relay straight from the battery to HID ballast, the heavy load is removed from stock headlight curcuit. Triggering the relay only requires 0.1 amps, so stock headlamp curcuit has no problem powering that. A relay is just a remotely mounted heavy duty switch, and the trigger power that goes to it just draws a small amount of current through the headlight switch to run an electromagnet that mechanically closes the contacts inside the relay which in turn hooks battery power strait to HID ballast power terminal. This insures that you wont ever overdrive the ratings of your vehicle's harness.
Most HID kits comes with some sort of relay. The important part is that the relay is powered through a high current curcuit like directly to battery. In this picture, relay works as a polarity converter. (As a side note, correct polarity is a neccesity to make the ballast work, so that is not bad.) The bad part here is that the relay does not releave the stock headlight curcuit from the start current peaks. Also the ground connection in this example goes through stock headlight wiring, which on most cars has too thin wires. This harness will function properly for a while, all depending on how oversized your headlight curcuit is. It might start failing after 100 start/stop cycles, it might take 1000, but on most cars it will eventually prematurely wear out at the weakest point. The parts mentioned in above DIY relay only cost a fraction compared to truouble shooting labour and parts in the headlight curcuit.
Most halogen headlights (not only dual filaments) are
designed to turn off low beams when high beams are turned on. This is more
of a engine overheating precautionary thing from the manufacturers than
a result of a lighting law cotaining of too bright total headlamps.
In theory, using a diode from each of the high and low
beam harness in series to trig relay so that low beams gets power even if
low beams turn off will prevent this. It works great if you have halogen
low beams, but not for HID low beam system. The downside is that if you
are driving during the day with your HID low beams off, and do a couple of
flashes with your high beam, you will notice that your HID system will be working
like crazy. Startup time for HID system is up to 10 seconds, so flashing like
this will only decrease life of your HID bulbs.
The actual "dark" time interval between low/high beam
shifts might not be visible when you run halogen bulbs. Halogen bulbs react
a little slow, so its hard to notice. We are talking of maybe 1/10 of a
second. But any HID system will turn off and restart. What you experience
on the road is dangerous pitch dark, 3-5 seconds.
This can be solved in a few ways, the first one is the
most elegant:
Igniting warm bulbs will draw more amps than compared to cold ones, so it is most probabaly insufficient 12V power feed. This could also be a sign of too low igniting voltage which means ignitor is defective. The ignitor in most HID setups is integrated in the ballast.
Yes. Activating relays is done by connecting voltage
to a coil, which in turn creates a magnetic field that pulls over the switch.
When voltage is removed from the relay, the energy that is stored in the
coil will send current the other way by increasing voltage to several hundred
volts, and a small arc will be visible between the contact elements of
the headlight switch. Over time, the switch will only work intermittant,
and will eventually totally fail. Thats why a serial diode is essential
to protect the headlight switch.
Both relay and Bi-Xenon solenoid (if equipped) needs to be triggered through diodes.
There is no rule of thumb of when to use diode or not without doing
a throughout internal study of entire internal headlamp curcuit, which is wasted time.
(An internal study means removing all related wiring, fuse and fuse sockets, connectors, M/F switch and headlamp switch. Then connect it together with 15 amps load at headlamp connector in a lab and let a robot turn it on and off for 5000 times.)
Note that relay needs a minimum 1A/100V diode, solenoid needs a min 3A/100V diode, because of a more powerful coil. Both of them are like $1.50 or something (less than 0.1% of budget), and if inserted at the right time of install, there are no extra time to do so.
It can be had from several places for $35 - $65. Just type in "Headlight harness" on yahoo.com and you will get at least 3 places on the first page. 99% of them are intended to decrease voltage drop in an Halogen headlight setup. This means in most cases you have to solder the connection to the ballast plug yourself. This is because halogen harnesses are ment to connect from and to the same socket (9006male -> 9006 female, 9007 male to 9007 female, H4 male to H4 female, etc). Better quality HID kits (like autolamps-online.com) comes with harness of various quality. A premade harness is designed to be long enough for all vehicles so be prapared to experience up one meter extra wire here and there.
Be aware that most aftermarked headlamp harnesses are made in Asia and does not have OEM quality and will detoriarate within 2-5 years. This is definatly an example of a product where u can say that you get what you pay for. $65 or less is not enough to manufacture and distrubute a high quality harness. If you want the best setup, make one yourself.
This description will work for low beams with a single filament (H1, H2, H7, H9, H10, 9006) bulb. Diode is inserted to protect vehicle headlamp curcuit. This makes polarity important. The polarity of headlamp connector in vehicle harness is not standardized, so you would have measure first before inserting diode in the positive wire. It only takes 1Amp to kill a 1N4005 diode, so do not short it.
Note the inserted 1N5404 diode. It protects high beam curcuitry:
Dual headlights means that original headlamps uses H4, 9004 or 9007.
You might think that below diagram looks too complex, and wonder why
factory headlight connector is NOT utilized to trigger relay curcuit. If relay
was triggered directly from headlamp connector, ballasts would turn off
when turning high beams on, which is an unlivable situation when using
HID system, because of start up delays. This diagram will pick up relay
trigger signal directly before high/low beam switch and will eliminate this problem.
By combining a typical headlamp stock curcuit diagram with our single filament diagram, we will
get the following diagram:
Yes! Painless Performance has an H4 headlight harness ( P/N 30815) that can be used a basis. By replacing the three H4 connectors with the style of halogen bulb connectors (9006, H1, etc) you use in your car. Those connectors are available in male and female types directly from suvlights.com's website. The Painless Performance harness contains two relays. One is ment for low beam and the other is for high beam. Even if u did not have in mind to upgrade your high beam as well as your low beam, this is your chance to integrate it. Halogen will dominate on the high beam scene for many years to come, so decreasing the voltage drop with a better curcuit will give more light output. It is probably the fastest way to get a quality harness for any retrofitting of any upgraded headlamp.
If you like fuse integrated relays, buy them from Hella.
Here is a table over easily obtainable single automotive high quality relays:
| Max Continous Load (Amps) | Brand | Model | Example of Retailer: | ~price in USD | Herman's notes: |
| 20-40 (100 inrush) | Omron | G8J series | digikey.com | 5 | P/N Z983-ND, sealed container. Picture. |
| 30 | Siemens | micro size relay, Series V23086 | newark.com, | 3.50 | with 1mm diameter pin PCB tabs - excellent for soldering followed by silicone potting! |
| 40 | Tyco | VF4-series | newark.com | 6 | with quick connect tabs |
| 70 | Tyco | VF7-series | newark.com | 8 | with quick connect tabs |
Waterproof relays (P/N 050453), socket (P/N 050455) and contact elements (P/N 050460) can be had from http://www.jpcycles.com. The waterproof relay looks alot like the Omron relay mentioned above.
Solid State relays will probably take over production of mechanical relays
in the future when production numbers go up.
Solid state relays have no moving parts and will therefor have
a much smaller chance of breaking. They do not have a trigger coil that sadly
has dreaded inductive current peaks, so there is no need for a switch protection diode.
In 2004, there were relatively few manufacturers of solid state relays.
Where to buy them:
Hella has them in various versions. Very few exists on the marked:
Route66 Supply.com
Rallylights.com
Hamsar Diversco - they have 6, 12, 20 and 40 amps versions available. Parts are orderable through Canadian Tire stores in Canada.
Fuses. "Littlefuse" has several versions of hanging and bracketed fuseholder,
which is a standard in vehicle electrics since the 1970s:
For the 15A fuse, use a blue colored "ATO" fuse:
For the 30A fuse, use a green colored "MAXI" fusible link:
Fuse holders. Place fuses in waterproof holders. ATO holder is pictured below.
(Holders for the MAXI is way bigger in volume than ATO)
Herman likes using goldplated wire terminals simply because of their
resistance to harsh liquids and fumes normally found underhood. Wire terminals are
typically available from car audio shops and online.
Ideally you would select a ring terminal for 12 gauge wire, but they tend to not have
big enough to hole diameter, so go up to 10 gauge. Hole diameter must be identical
or slightly larger than battery posts screw terminals. Terminals are typically of "crimp"
style, which means that wire is "squeezed" onto terminal. Do not crimp terminals
under hood. Soldering is the way to get good electrical connection.
Wires must also meet certain specifications. Hardware stores sells 12AWG wire, but its not suited for automotive use: It may not contain more than 6-10 twisted copper wires. That low amount makes it too stiff and prone to internal breaking. Also, they might only have standard PVC electrical insulation, which is only good until 80C (176F). There are many places (like radiator, engine, oil cooling ducts) that are hotter than that. When temperature drops below freezing, these wires becomes even stiffer and impossible to handle.
A good automotive cable has a minimum of 15 thin wires of copper or
even better: silver plated copper. Insulation should be marked with minimum
of 105C (221F). This way you can actually connect ground wires to the engine
block without risking insulation going up in fire, and you are not limiting
yourself when it comes to cable routing. Higher insulation temperaturs
than 105C are available, but very hard to get a hold of.
If you have a hard time finding good cables new, Herman have found
out that it is actually better to rip out some 3-6 year old cables from
the junk yard, than to buy some half decent ones. Just make shure you cut
off a few inches at the end to make shure you do not have any corrosion.
Another good source for 105C and 135C rated wires are old micro wave
ovens and dryers.
KJCO (California) is a good online place to buy automotive electrical stuff:
Wires must be protected against mechanical wear. This is basically a thick walled flexible tube. Use conduits (also known as looms). Place a bundle of isolated wires inside. Action2k has this and accessories (loom retainers, tees and terminators).
Digikey.com (or .ca) has 1amp and 3amp diodes. Just search for 1N4005 respective 1N5404. 1N4005 is almost too tiny in comparison to diameter of 12-14 gauge wire, so using the 5mm diameter 1N5404 for all diode needs is a good choice.
Ground switched headlights
Most cars on the market use positive side switching.
However, there are a few models (Toyota, Datsun, Nissan) that has ground
switched headlamps. The above wiring diagram can still be used, the most
important is to make shure current goes the right way through the diode.
Here is more info on ground switcing: http://store.yahoo.com/bcssales/grounlowsids.html
Will incresing the supply voltage to the ballast give
more light output?
No. After igniting, the ballast will generate the needed
voltage to the HID bulb regardless if the ballast is powered with 10 or
15 Volt. The ballast compensates itself for voltage variations. At 10V,
the ballast will draw more current than at 15V.
Generally, a quality HID setup that originally came with halogen bulbs would use relays to get the power directly from battery. Which would mean that after you install your kit, load will go down from 55W to ~1W on headlight curcuit. This will most likely be recognized as a "bulb out". There are several generic ways around this and here are some work around suggestions:
Just like all other Bi-Xenon units with moveable cutoff shield to get high beam, this one also has a solenoid to operate the shield. Solenoid is only pulling one way, there is a spring that will move it back. Solenoid operates after "pull" and "hold" principals. Which means that solenoid must be activated in pull mode and held in place by the hold mode. There is three wires coming out of the solenoid. Color coding varies, but it seems like these colors are the most common:
An electrical abd hookup diagram will look like this:
By using an ohm meter, it is possible to determine what wires goes where, even if they all have same colors.
When high beam voltage (12volts) is applied, the capacitor will shorten for a brief period of time, pulling the relay and giving power to the pull coil of solenoid. The hold section of solenoid will then maintain its position until power is removed. It should be mentioned that if coil resistance in relay is lower than 60-100ohms, capacitor might need to be increased. Maybe 2200uF/25V or 4700uF/25V. This will increase hold time. Note that a 4700uF/25V is probably larger than relay itself.
If you do not like to use relay because of reliabilty issues, an exmple of using a MOSFET switch will come soon.
Warning: Attempting to connect red and black permanently to a vehicles high beam will make almost 30W of heat to be emitted from solenoid. Solenoid is not designed for that and will start fuming up all cold (reflector, lenses) surfaces in your headlight.
Copyright 2001 - 2004 Automotive Lighting FAQ.
