wiring relays

[Davemate]

it would seem that before i go ahead and buy some halogen headlights, some people on here have been saying about by-passing the headlight switch with relays to get more power to the sealed beams as the light switch sapps a volt or two causeing a weeker headlight
question :-
               can the relay be fitted under the dash with the headlight switch on /off activating the relay ie:-


splice in the relay feed from the headlight switch to activat the relay
then
the new power feed would go through the relay(when activated) and along to the original dip/main beam
leaver on the column and then get sent to the dipped or main beam via the original loom

is this ok to do, will the original loom take the increase in volts
or do i have to fit two relays 1 for dip and 1for main
and fit them near to the headlight and run a new feed all the way down the the realys

i hope this makes sence
Dave

[Richard B]

No you really want two relays, one for dip and one for main. Otherwise you will still get voltage drop from the column lever switch.

I did this on my MkIII Spitfire and the lights are noticably brighter. No problem with the loom taking the "correct" voltage.

Split the bullet connectors at the steering column by the parcel shelf.  

Take two thin wires (Blue/White & Blue/Red) off to switch the relays from the steering column.
Take two thick wires  (Blue/White & Blue/Red) from the switched feeds of the relays to the wires going to the headlights.


This way if you have problems, you can just reconnect the column switch wires to the headlights wires and bypass the relays.



Hope this makes sense  :-/

[Davemate]

yes it does and thanks!
it will save me running wires down to the front of the car  :)

[piman]

Hello Dave,

Richard's way is easier but the best way to get maximum volts at the lights is to run heavier gauge cable from the battery to the power side of the relays and ideally mount the relays close to the front and run new cables from the relays to the lamps. I don't know what car you wish to do this to but on my 2000 I have a separate cable for each filament, i.e. don't pair filaments off one cable as the original installation is done. If you intend to use a fuse, don't just use one but again fuse each filament separately. If you use one only on the feed side, a blow (or poor connection) looses all your headlights.

Alec

[James]

I agree with Alec - if you're doing this on a small chassis car (which I think are fairly similar with their wiring) then there are double bullet connectors down at the front of the car above the grille etc. Do what Richard says but at the front of the car. You only need a couple of bigger cables going from the battery via a fuse to the front. Mount the relays inside the wing (p-clips to bonnet tubes etc)

[Davemate]

piman wrote:

Hello Dave,

Richard's way is easier but the best way to get maximum volts at the lights is to run heavier gauge cable from the battery to the power side of the relays and ideally mount the relays close to the front and run new cables from the relays to the lamps. I don't know what car you wish to do this to but on my 2000 I have a separate cable for each filament, i.e. don't pair filaments off one cable as the original installation is done. If you intend to use a fuse, don't just use one but again fuse each filament separately. If you use one only on the feed side, a blow (or poor connection) looses all your headlights.

Alec

the car is a herald 1200
so it would be best to run 4 new feeds(with their own fuses) to 4 relays ---one for each filament(two each side)
or am i missunderstanding ?

[piman]

Hello Dave,

two relays, one for dip and one for main.

If you like send me a P.M. with an e-mail address and I'll send a simple diagram?

Alec

[Davemate]

have done
thanks

[James]

Please share on here Alec - it would be useful for everyone.

James