How do I align fog/auxiliary lights?

[belfert]

My bus came with fog/auxiliary lights factory mounted in the bumper.  The lights were shot when I got the bus so I replaced them both.

One of my friends was driving and said drivers were flashing him when the aux lights were on so I assume they aren't aligned properly, but I have no idea how they should be aligned?  Any suggestions?  (BTW, both lights quit before the trip was over.  One lens broke and the other doesn't light anymore.)

[Paso One]

 The  headlights  can  be  aimed  using  a  mechanical aimer or a wall screen. Either method assures that the headlight beams point in the direction specified by the vehicle  manufacturer.   Headlights that are aimed too low or to one side will reduce the operator's visibility. To  ensure  that  the  headlights  are  properly  aimed, you should have a half a tank of fuel, the correct tire pressure, and only the spare tire and jack in the vehicle. Some  manufacturers  recommend  that  someone  sit  in the   operator   and   passenger   seats   while   aiming   the lights. HEADLIGHT  AIMERS  are  a  device  for  pointing the  vehicle  headlights  in  a  specified  position.  They may  be  permanently  installed  on  a  track  or  may  be portable.  Some  require  a  level  floor,  and  others  have internal leveling mechanisms to allow for uneven shop floors. To use the aimer, follow the instructions for the specific type of equipment. The  HEADLIGHT  AIMING  SCREEN  is  a  series of measured lines marked on a shop wall or on a framed easel for aiming the headlights of a vehicle. The screen should be no less than 10 feet wide and 42 inches high. When it is mounted on an easel with casters, the screen should be no more than 12 inches from the floor. To comply with regulations of most localities, you should place the screen 25 feet ahead of the vehicle. The  accepted  driving  beam  pattern  for  passenger vehicles  will  show  the  high  intensity  portion (hotspot) of the light rays centered on a horizontal line that  is  2  inches  below  the  center  or  horizontal reference  line  on  the  screen  (fig.  2-63).  This  means that there will be a 2-inch drop of the light beam for every  25  feet  of  distance  from  the  headlight. Headlights   on   large   trucks   present   a   special problem because of the effect of a heavy load. At the same 25 feet, truck headlights should be aimed so that none  of  the  high  intensity  portion  of  the  light  will project higher than a level of 5 inches below the center on  the  headlight  being  tested.  This  is  necessary  to compensate for the variations in loading. When using a screen for aiming the headlights on a vehicle  that  uses  a  four-headlight  system,  adjust  the hotspots of the No. 1 (inboard) lights so that they are centered   on   the   vertical   lines   2   inches   below   the horizontal line (fig. 2-64). The low beam of the No. 2 (outboard) lights is aimed so that the hotspot does not extend to the left of straight ahead or extend more than 6 inches to the right of straight ahead. The top of the hotspot of the No. 2 lights is aimed at the horizontal line. When the No. 2 lights are properly adjusted, the high beam will be correct.

[Tim Strommen]

One comment be fore I answer your question - if you have "aux" lights, they should only be on when high-beams are being used and should be "off" with the low-beams.  Fog lights are only to be used with low beams and should be "off" with the high-beams.

Fog Lights have a very obvious cut-off if they are true fog-lights:


See this document by Daniel Stern (really nice guy by the way)...  The basic jist is, if the following conditions are met, do the follwing:

• measured height of light 0" to 18" from ground, then @ 25' the cut-off shoud be @ -1.5" the light height
• measured height of light 18.5" to 28" from ground, then @ 25' the cut-off shoud be @ -3" the light height
• measured height of light 28.5" to infinity from ground, then @ 25' the cut-off shoud be @ -4" the light height

-Tim


[edit] Paso One has some good pointers, make sure the bus is in the typical operation condtion (load, fuel, etc.) if you have manual air valves or air up the bus properly if they are automatic.  I like the Daniel Stern method, as you can do it on any flat road with a tape measure (without hauling around a sheet of plywood, or a giant sheet and frame with lines on it).  You also need to make sure your lights are aimed straight (like Paso One mentions).  You can do this by parking against a "straight edge" in a parking lot (the concrete curb), and taking a measurement of the distance from the curb to the light, then at 25' you mesure where the hotspot is (or in the case of a fog light, find/measure the edges of the beam from the curb and divide by two) - the two values (at the bus and at 25') should be the same.  In order to work on one light at a time, just have someone stand in front of or put a jacket over one of them.  With our auto-ride height air-valves, the bus should automatically keep the at the correct height for each corner, thus loading differences should not drastically affect the aim of your lights... [/edit]

[bobofthenorth]

Paul has given you the theory Brian.  In practice what I did was lean two sheets of plywood up against the fir trees on the edge of the yard.  I aired the bus up and parked it 100 yards away from the plywood. I sighted down the driver side of the bus and lined the plywood up so that it stopped in line with the side of the bus (think plywood in the driving lane, stopping at the centreline of the highway).  Then I waited until after dark.  My fog lights didn't have any formal adjustment available on them so I had to beat and bend the brackets until I was satisfied with the pattern, which was more or less what Paul has already posted.  For the high & low beams I had the adjusting screws so it was a bit easier to make the adjustments.

[belfert]

My fog/auxiliary lights only come on if the headlights are on low beam.  When the headlights are on high beam the fog lights don't work.

I thought my fog lights didn't work after I replaced them, but I finally noticed the high beams were on and turned them off.  Voila, the fog lights started working.  I just figured there was a government that fog lights couldn't be on when the high beams are one.

I'll have to try the suggested alignment methods once I get my fog/aux lights working again. 

[Nusa]

Don't ignore what Tim said and group Fog and Aux lights together. They've got separate functions, and can only be set up to do one or the other job well, not both.

Fog lights are meant to see in foggy conditions...they're aimed so you can see the road in front of you without creating blinding glare in the fog like high beams would. You can't see very far in real fog, so you are going to be going relatively slow to be safe anyway.

Driving/aux lights are meant to increase the amount of light you're tossing out in normal road conditions, particularly when nobody else is in sight. They're aimed based on your needs, usually much the same as your high beams (and should go off when high beams do, for the same reason).

[belfert]

Okay, I guess what I have are really auxiliary lights and not fog lights.  I recall now that the operator's manual for my bus does call them auxiliary lights.  I still need to align them.

I guess I am used to people calling any low mounted lights fog lights.

[HighTechRedneck]

Brian, as Nusa said, if they only work with the low beams, then they should be fog lights.  If they only came on with the high beams then that would indicate they were aux lights.

[gus]

Usually the bus manual has a very good description of all front light alignment.