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Re: Headlamp relays Help!

To: "John T. Blair" <jblair@exis.net>
Subject: Re: Headlamp relays Help!
From: "G.J." <johnsong@is.dal.ca>
Date: Sun, 5 May 1996 12:49:33 -0300 (ADT)
On Sun, 5 May 1996, John T. Blair wrote:

> Greg,
> 
>   You are absolutly correct on your planned wiring layout.
> 
> You ask: "How do I set the headlamp relays "in parallel"?
> What do you mean?

I'm refering to the article on upgrading your lighting system in the SOL 
tech section.  it states :

"At the very least, you want a relay and fuse on the high beam circuit. 
The best (and easiest!) way to
do this is to buy a fused Marchal 514 relay. They're bulletproof, and can 
easily be spliced into the
high beam circuit. Find some source of unswitched 12V (brown wire, you 
want a heavy one). Find
the blue/white wire leaving the dip switch (usually there's a connector 
that connects the switch, the
lead out to the lamps, and the indicator - this is a good spot). Connect 
the brown wire to the source
terminal on the relay. Connect the U/W wire coming from the switch to the 
coil. Connect the U/W
wire going to the headlamps to the load. Make a good coil ground. Voila! 
You now have brighter
high beams, even if you didn't change the lamps. (If you're particularly 
anal, wire the new harness
with appropriate colors - I would use blue/slate for the lead that 
splices from relay to the headlamp
wire). Use heavy wire for the load connections - 14 gauge. 

...snip...

Now, if you're having fun, you can rig a *parallel* relay for the low 
beams. If you're going to do this,
then consider not using two Marchal relays, but two unfused relays, 
*sharing a single source*, which
you fuse. "

end quote.

Oh.  I guess that doesn't really mean "parallel vs in series".  How do I 
share a single fusable source? I have 3 of these relays I'm going to use. 
Is a 20 A fuse good enough?  

My driving lamp switch has 2 wires , one goes to the light and one to 
power.  I take it the one going to power remains (I have it hooked to 
ignition so they turn off automatically with the ignition;will they still 
do this? or do I connect the #30 connection on the relay to the coil?) and 
the other 
goes to number 85 on the relay?  I'm putting the relay as close to the 
headlights as possible (where the U/W splits to the headlights for the 
high beams for example).

> If you try to put the actuator side (the relays) in parallel or the
> output sides in parallel, you'll have a problem.  Any time you turn
> on any one item, they all will be actuated.  

So I should give be able to run all of the 30's to a single fuse and then 
to the battery, and the 86's to a common ground?

> 
> >Here is an ascii diagram of a BOSCH 12V 30 A relay that I plan to use to 
> >relay my headlamps, one for wach of low beam, high beam, and driving 
> >lamps.  
> >
> >      85        87    87
> >       o         o----o 
> >    ___|__     \
> >   |   /  |__ __\
> >   |  /   |      \
> >   |_/____|       o
> >       |           30
> >       o
> >      86
> >
> >This is the diagram on the side if it.
> >
> >I want to double check what connections would work.
> >
> >87's    to right and left lights 
> >30      fused to brown (battery)
> >86      ground
> >85      to switch.
> >
> >What am I missing? How do I set the headlamp relays "in parallel"?
> >Setup is for a 72 MGB.  Wiring is 14 guage.
> >

Thanks John.

Greg
    ________         ___
   / ______/        |   |  Greg A.M.Johnson           '72 & '66 MGB
 /   \   ___        |   |  Biology Dept.
 \     \_\  \  /\ __|   |  Dalhousie University
   \______   / \________|  Halifax, N.S., Canada
          \/  
   * See the British Automobile Touring Association of NS Home Page!*

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