Dastardly Dimmer Switches
I observe with much interest the discussion in recent issues of UniqueCars with respect to f loor mounted headlight dimmer switches.
The concept of changing headlight beams while keeping both hands on the steering wheel is a sound one.
However I can totally empathise with the experience shared by Paul Hamilton (UC434) with respect to headlights going out at highway speed on a dark night.
It should be noted, one of our highly respected Australian heav y vehicle manufacturers based in Victoria, for many years, in several of their model lines, mounted the headlight dimmer switch on the f loor, and, by design, was required to be actuated by the driver’s heel. One might speculate, that, on this occasion, Mr Hamilton may have been the victim of this design as I am aware of many similar occurrences, where headlights have gone out at night and catastrophic crashes have resulted.
This manufacturer now uses a multifunction steering column mounted combination switch for the control of park/tail lights, headlights HI/LO beam, windscreen wipers/washers, horn, and turn signals.
Over several decades working as a practicing heav y vehicle electrician I have had reason to modify many headlight control systems to avoid the perils of f loor-mounted headlight dimmer switches, which, by design and their placement either as on the f loor type or through the f loor type, are subject to the ingress of gravel particles, dirt, dust and despite the manufacturers best efforts to prevent it, inevitably moisture ingress.
Moisture reacts on the dissimilar metal combination at the wiring loom / dimmer switch connection which causes severe corrosion resulting in an open circuit situation, and in more severe cases causes the terminals to separate from the switch assembly resulting in a headlights-out situation.
The gravel/dirt/dust combined with moisture eventually turns into a concrete like substance which causes the f loor mount dimmer switch to become inoperative, which at best prevents beam selection, at worst, will prevents any and all headlight operation, guaranteed to prevail at the most inappropriate time, that is at highway speed at night.
Modification actions range from the simple relocation of the existing dimmer switch and associated wiring looms from the f loor to a convenient position on the dash/instrument panel to
“THE HEADLIGHT DIMMER SWITCH ‘WAS ACTUATED BY THE DRIVER’S HEEL”
a more safety orientated sophisticated system of change over relays for HI/ LO beam selection, and standard relays for load switching, the system actuated by a push / push dimmer switch incorporated in the handle of the turn signal switch, resulting in a system that defaults to LO beam in the event of a dimmer switch failure.
Emergency lighting systems have been developed by myself and no doubt many other professionals in the field in order to safely allow a vehicle to come to a halt, or continue at reduced speed until repairs have been effected.
Emergency lighting systems range from powering up the inner LO beams, which appears to have found favour with long distance passenger coach operators (four-headlight systems) to independently powering up the bull lights on heav y trucks.
Emergency lighting systems similar to those described here may not meet the relevant vehicle standards. However when used in a sensible manner, it has the potential to prevent a major crash and save lives.
I would most sincerely urge the readers of this fine family publication, should the headlight system installed to their vehicle need attention, repair and or upgrading to please consider the forgoing as well as the most serious implications with respect to the safety of themselves, their passengers as well as other road users in the event of headlights going out at highway speed at night.
Only the best quality wiring, connectors, switchgear, relays etcetera must be used, the cost of same must always be a very secondary consideration.
Circuit design must be proven sound, if in any doubt, please present same to a professional Automotive Electrician for assessment.
Wiring must be very carefully installed so that it is protected from road grime and abrasion, secured correctly to avoid physical damage for the prevention short or open circuits.
Hopefully these observations will prove to be of interest to the team and the readers of UniqueCars.
As always, enjoy receiving
UniqueCars, many thanks for a ver y informative, interesting and entertaining magazine, features and editorial content well done every issue.
Cheers and thanks for the opportunity to contribute to current items of debate. Mac Carter
Townsville Truck Electrics