Jerry Causey writes:
> Today I installed new (courtesy of JC Whitney - Polish lamps, Korean
> bulbs, American relay) 90W / 130W, H4 headlamps, and a relay in my
> 1967 MGB GT. It seemed pretty straight-forward, but I have a problem.
> The relay has two terminals marked "SWITCH" to which I connected
> two approximately 12 gauge wires, one blue with white and one blue with
> red which come from the dimmer switch, according to my Haynes
> manual. There is another set of terminals marked "LIGHTS" which I
> connected to the slightly thinner (14 - 16 gauge) duplexed wires which
> actually run to the headlamps. So far, so good. Last, per the instruction
>sheet,
> I connected a 10 gauge wire from the relay terminal marked "BAT" to the
> unfused, hot side of my fuse block (the relay has fuses).
>
> The problem:
> My headlamps are on all the time, independent of the light switch on
> my dash. Did I do something wrong, or did I just get a bad relay from
> JC Whitney? HELP!
Check the schematic for the relay, but it sounds as though one side of
the "SWITCH" terminal should be connected to the switched side of your
dimmer switch, and the other side to ground. "LIGHTS" and "BAT" sound
good.
You have the wiring gauges backwards. The "SWITCH" terminals should
carry very little current (I haven't measured, but I'd imagine it's on
the order of milliamps), so should only require 14-16 gauge wire. The
headlamps (ESPECIALLY since you're running 90/130 bulbs) should get the
big wire (10-12 gauge) for carrying all that current. Don't forget to
use the same gauge for the lamps' ground wires.
When I installed my JC Whitless Polish/Korean specials, I used two
relays: one for the high-beam and one for the low-beam circuit. I
disconnected the stock headlamp sockets at the nearest Lucar connector,
and used that junction for the "SWITCH" terminals on my relays (this
wire appears to only be 14 gauge). The big juice for the lamps comes
via fused 10 gauge wire running straight from the starter, where the
positive battery cable connects. 10 gauge ground wires connect to the
chassis behind each lamp.
These lamps are actually very good, considering their cost ($21 each).
I use the 55/60W bulbs, and I get lots of bright, white light, which I
attribute as much to the 10 gauge wire as to the lamps. When the bulbs
go, I'll try 55/100W. 60W x 2 = 120W, which, at 12VDC, is 10 amps
(slightly less at the usual 14VDC while the alternator is charging).
For your setup, 130W x 2 = 260W, or almost 22 amps at 12VDC. Make sure
both the relay and the fuse will pass this much current (I don't know
how to calculate current carrying capacity of 12 gauge wire, but it
should be okay).
I hope that nobody out there is using H4s without a relay. I, in my
impatience, connected mine to the stock wiring for a couple of days, and
the wires coming through the headlamp switch were uncomfortably hot
(it's easy to stick your hand under the dash to feel them). Don't take
chances!
Lastly, though this is turning into an extended epistle, I'll throw out
my blanket recommendation to all North American residents: junk those
sealed beams and buy some H4s! The difference is (if you'll excuse me)
like night and day. And the 55/60W bulbs are now available at your
local MegaMart and AutoStore, under their US designation of 9003 (HB2),
for about the same price as the sealed beams.
--
Todd "I can SEE!!" Mullins
todd@nutria.nrlssc.navy.mil On the lovely Mississippi (USA) Coast
'74 MGB Tourer with decent lights, finally
"A life lived in fear is a life half lived."
|