The dimmer switch is primarily used to switch between the high and low beam headlights however in many vehicles it also controls the vehicle s interior lights as well.
Old car high beam switch.
The difference is that some vehicles have a separate relay just for the high beams and the high beam passing or dimmer switch may or may not be integrated into the headlight switch.
That s 20 in the diagram.
Up through the 80s.
I remember a 1978 mercedes 300d that my parents bought new being the first car i drove with the high beam control on the stalk.
In most cases the failure of high or low beams is due to a relay or switch problem and the troubleshooting procedure is similar to the one outlined above.
My 1977 lincoln mark v had the high beam switch on the floor.
A temporary solution to this is to turn the high beams on and off quickly several times which could clean the contacts in the switch.
Switching between low and high beam was accomplished through a switch on the steering column.
We see this more on cars with their headlight switch on the steering column.
It doesn t take long to restore fogged headlights and night visibility.
In 1925 the depressible headlight became obsolete when the guide lamp co.
In 1927 the dimmer switch was moved to the floor where it stayed for about 50 years until it was moved again to the steering column.
My 1962 and 1949 cadillacs have the switch there as well and the 49 has a push button on the dash near the key for the starter.
The larger blue red wire from the other relay goes to the low beams.
Some had other interesting things like foot operated windshield washers too.
For some vehicles it is a button switch located on the driver s side floor 1960s to mid 70s gm vehicles while on other vehicles it is mounted on the steering column.
If the high beams function but don t seem to light your way especially if you drive an older vehicle with polycarbonate headlight lenses your car may be a victim of headlight fogging this isn t simply scuffing but an actual chemical change from polycarbonate s exposure to solar ultraviolet.
Dimmer switch built into the headlight switch.
The high beam switch turn signal switch is malfunctioning the high beam indicator gets power directly from the wire that connects the high beam switch to the daytime lights module.