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Headlamp Conversion
Home Up Headlamp Conversion Terms




Conversion Headlamps replace your original manufacture's headlamps, and not only give superior lighting, but also flexibility in the amount of lighting to be used.

Hella, a German company,  and Cibie' a French company still makes these for sale.  The last ones I bought the dealer is no longer in business.  However at the time of this update Carolina Classic Trucks had them inexpensively, or they are available from Ken Beard at Susquehana Motorsports.  Moss Motors sells a British version made by Wipac (162-725), but I prefer the German made Hellas.

These lights replace your standard headlights, but provide a much better pattern (see below).   As you can see this pattern is strongly cutoff to the left and top.  This means that more light is placed on the road where you need it, not in oncoming driver's eyes, and not in illuminating the tree tops.  This also means that you can run with higher than normal (55W/65W) and actually your headlights show less glare to the oncoming traffic, and anyone you may be following.


Left Side e-beam pattern.GIF (2470 bytes) Right Side

Conversion headlamps come in Single Round, Single Square, and also for four headlight installations, so the pattern may vary slightly from the illustration, but it won't vary much.  There are four advantages with using conversion headlights over standard or replacement headlights.  

  • The pattern puts your available light where you need it on the road, not in the oncomming traffic lane or lighting the tree tops.

  • the sharp cut off makes this an excellent fog light as well.  Fog lights are also cutoff sharply at the tops, and should be mounted low so that they don't light the fog or precipitation at eye level, thereby increasing glare, and reducing visibility.  (People who drive with their high beams on in fog are reducing the amount they can see, because they are actually causing the fog to reflect their own light back in their eyes!  The only exception was a rally car I used to have, that used Aircraft Landing Lights for High Beams.  That with 4 fog lights, and 5 driving lights put out so much heat, that it must have raised the temperature slightly above dew point (about 3 degrees F) to burn off the fog.  That is a real exception!!  Normally in a foggy situation, or during heavy rain or snow, I like to turn my headlights off, and run with just my Fogs and parking lights.  I see better, and I don't get the harsh glare of my own headlights back in my face which tends to tire me on longer trips.)

  • The High Beam Pattern works as well or better than most driving lights.  Thus, you may avoid the need for driving lights.  If you have a driving light since your high beams are more effective you can now set your driving lights for a longer reach (1/4 mile ahead) if they are focused tightly enough.

  • You have the choice of wattage and selection of color, and the bulbs are replaceable.

Thus you may want to opt for conversion headlights instead of fog and driving lights, which tend to get broken during parking, and in my opinion spoil the look of the B.  Both my TD and B sport conversions, but only the TD has fog/driving lights because I like that look.  The major disadvantage is that they are not sealed.  Cibie' made a conversion headlight using bulb within the bottle technology (they called it BOBI), but I haven't seen them for a few years.  Not being sealed means moisture can get into the headlamp assembly itself.  However by ensuring that you install the headlamps according to instructions by placing the vent in the proper orientation so that any accumulated moisture will be dissipated, they are as trouble free as any sealed beam I know of.   The other disadvantage is that you can not touch the glass envelope of the bulb which at times leads to some awkward contortions.  

The single 7" headlamp per side such as the MGB and MG T series use a dual filament bulb of type H4. Normal auto headlights are 55W/65W, that's 55 Watts on low beam, and 65 Watts on high beam.  Normally these headlamps come with a 55W/65W standard white H4 bulb, and will install without modification.  However you are not limited to using a 55W/65W H4 bulb.  There are several choices available up to and including 100W/145W which is twice the output of a standard light.  There is a catch to using anything greater than 55W/65W H4's.  

If you check your wiring, your headlamps are wired with about 18 AWG wire and at 65W will draw about 5 Amps.  If you were to put in 90W/130W or even 80W/90W the lamps will be drawing between 7 Amps and 10 Amps each.  Most standard lighting cannot handle this current, and you will most likely fry your headlamp wiring.  To prevent this, you can add an auxiliary harness.  

An auxiliary harness is simply an additional harness wired with relays.  There is a plug for each headlamp, a wire for ground, a wire that connects directly to the battery, a relay box, and one extra plug, which is a male end and looks like one of your headlamp connections.  Its function is to switch the relays appropriately.  To install the harness, simply route the wiring to each of your headlamps (see the footnote concerning routing on the MGB).  I installed a PIA harness on the MGB, but they are no longer available from PIA, however, Competition Limited does sell one, though I have not used Gene's harnesses, so YMMV  (your mileage may vary )  I installed my harness in about 3-4 hours on the B, normal installations in other automobiles can take only 30 minutes, but then you don't have to fool with those buckets.

You may also want to select another color.  In France headlights give off a yellow color.  QI bulbs come in amber, or the lenses may be dyed yellow or a special yellow glass (remember how hot these get) sleeve fits over the bulb.  Either technique reduces the light output by 30%.  PIAA sells an H4 bulb called their ion crystal bulb which produces a yellow light, but only reduces the light output by about 5%, they are expensive and sell for about $30 per bulb.  (Note:  PIAA does not list its ion crystal bulbs on its web site, but they are still for a limited time in the supply chain).  More popular now are the very blue white bulbs that look much the same as the expensive Xenon Discharge Lights available on the late model high-end German Vehicles.  BTW, these bulbs are also available in 9000 series for your daily driver if you would like -- the same precautions apply and consider the heat output on the polycarbonate lenses modern cars use.  The human eye is more sensitive to yellow light, but even with only a 5% reduction in light output, you loose more than you gain with yellow lighting.  Where yellow lighting is useful is during winter, where the white snow cover will reflect back enough light that you can lose definition between the snow covered road surface, and the shoulder. However, in these conditions I prefer an alternative.  If you don't plan on driving  in the snow, then stick to the whites or blue whites.  These special coated bulbs are expensive (about PIAA =$35 each, Competition Limited = $16 each as opposed to vs $9 for a standard H4) but they can last for years.

Remember to adjust you lights to manufacturers specifications to make effective use of this improved lighting.

One last modification can be made to your conversion lights if you want to max out every available photon.  When you switch your high beams on the low beam filament is switched off, so you can see further down the road but close in is not as well lit.  By adding an inexpensive relay (under $5), available at most auto supply stores, you can light the low beam filaments at the same time.  This hook up is shown in a word document schematic diagram.  Click here to download. Note in the schematic provided, that there is an auxiliary fuse in this circuit since your normal fuses will not protect your low beam wiring using this set up.  One note of caution, this does put an additional load on your electrical system, dynamo/alternator, and regulator, ensure that they are capable of handling rated power prior to attempting this mod.   Do not skip installation of the relay, as the dip switch contacts will not handle the power.


On the MGB the headlights are in a bucket, and the wire feeds through a big formed grommet.  The following operations were performed to each headlamp assembly to install a PIAA Harness.

  1. With a small screw driver carefully so you don't scratch the chrome, or paint pull the chrome trim rings away from the headlamps.

  2. Remove the steel ring surrounding the headlamp by removing the three small screws holing it in.  Try not to let the light fall out as you remove the retaining ring.

  3. Remove the sealed beam headlamp from the bucket, and disconnect the plug from behind the headlamp.  Make note which color attaches to which spade connector on the back of the headlamp (you may want to write this down if your memory is as bad as mine)

  4. Remove the bucket from the fender by removing the three screws that attach it to the fender.

  5. With a small screw driver remove the connectors from the plastic socket that attaches to the headlamp.  You can then remove the wires and the grommets from the bucket.  Note which wire went to which position on the connector.  The female spade connectors lock in to the connector with a small tab that is spring loaded inside the headlamp connector.  Put the small screwdriver in from the rear of the connector so that the blade of the screwdriver compresses this tab, and withdraw both the screw driver and the connector from the rear of the connector body.  Do the same with the connectors for the new wiring harness.

  6. You can now remove the MGB's headlamp harness (the one that is not on the same side as the new harness male connector), and insert the new harness through the opening, and reassemble the wires into the connector by sliding them back into the rear of the connector until they lock (a jewelers small screwdriver helps alot with this whole operation).  The PIAA Harness came with plastic split loom tubing (Radio Shack 278-1654) which I also ran the one stock headlight wiring through.  Feed the split loom tubing through the hole in the headlamp bucket, and seal the hole with a generous application of silicon sealant.

  7. Replace all the parts and hook up the harness per manufactures instructions. 

Last modified: April 26, 2005

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