Terry,
I'm not sure I understand your question.
Relays typically have 4 or 5 terminals. Two terminals for the control side,
and two (sometimes 3) for the high power side. On the control side, one
side of the relay coil is connected to power, and the other side is
connected to ground. A switch is installed on either the power side or the
ground side. For headlights, the power side would be switched. On the high
power side, one terminal is connected to the power source, the other to the
load.
When the control side has both power and ground, the coil energizes, and
pulls the high power contacts closed and the lights work. If one side on
the control circuit is not grounded, the circuit will not be complete and
the relay won't energize.
Many relays conform to DIN standards and have DIN terminal designations, so
if you buy a off the shelf relay you might find the following terminal
designations:
86 Control side usually connected to power
85 Control side usually connected to ground
30 (or maybe 15/30) power supply for the high power device to be controlled
87 Load
87A Second load terminal, might be wired to come on at the same time as 87,
or on when 87 is off.
For wiring headlights you would most likely use 2 off the shelf 4 pole
relays, or one specialized headlight high beam / low beam relay
If I recall correctly I sent you a copy of using a Volvo headlight relay a
while back, if you misplaced those I can send them again, or I think Ed put
them up on his site.
Rick
On Wed, Jun 8, 2011 at 6:32 AM, TERRY COLL <coll44 at msn.com> wrote:
> I want to install headlight relays in my '64 BJ8. Does it make a
> difference
> if headlight relays are grounded? I've seen the grounded ones on-line but
> I
> really can't see the need.
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