dnmalc
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| posted on 26/5/10 at 05:23 AM |
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Rating of Relays & Fuzes
The sierra uses a seperate fuzes & relays for each dipped and full beam circuit which means that I end up with 4 relays and 4 fuzes for the
headlights alone if i use a single relay for high beam and a second for dipped does anyone know if the ones ford used are man enough or do they need
to be up rated.
Similarly given that the non surge rating of the fuzes are 15, 15 7.5 and 7.5A respectively one would believe that I was powering an arc lamp on the
front rather than circa 200W of lamps. So what fuze ratings are people using for the haedlamp circuits.
Thanks
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Stott
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| posted on 26/5/10 at 07:02 AM |
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I'm using 10a for each filament both dip and main, (4 fuses)
On my Sierra, there was only 1 relay needed, for the dip beam. The main beam switches through the comlumn stalks.
All of the other relays shown in the diagrams are for things like the driving and front fog lamps which are not needed in a 7
Cheers
Stott
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dnmalc
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| posted on 26/5/10 at 08:19 AM |
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Thanks for the input, my rational was that rather than using 2 off 7.5 A fuzes for the 2 dipped beams, as they only take 110W (circa 10A) these could
be routed via one 15A fuze and one of the existing main beam relays. However, the real question is do the two main beams which are rated at circa 65W
each really need individual relays and fuzes able to source 180w for each light. I would recon to use one 15 A fuze and one of the existing relays
without issue. .... or have I missed something?
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MikeRJ
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| posted on 26/5/10 at 09:55 AM |
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Headlamps should be individually fused, but powering both off the same relay should be ok. Note that whilst the nominal current for a 55W lamp
will be just under 5 amps, the inrush current will be many times this value, 50 or 60 Amps would not be unreasonable with high battery voltage.
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Stott
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| posted on 26/5/10 at 12:20 PM |
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fuse them seperately, every filament has a fuse for dip and main, sides are left and right fused normally.
You don't need a relay for each main beam filament, only one for the pair. Or alternatively, if you have sierra column stalks like I do (square
hazard button on top - no horn push - that's on the wheel) you don't need a relay at all, the switch itself is rated for the current.
Depends what switches your using, as above. Are you using the sierra fusebox? I am and it had a dip relay in there, and also driving lamp relays, so
all the wiring and individual fusing is in place for you
As for the fusing, it's best practice anyway, or else you'll lose both headlamps if one side of the wiring goes to ground, that would be
hairy at a ton in the dark.....
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dnmalc
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| posted on 26/5/10 at 12:21 PM |
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Whilst inrush currents are substantially greater than the ratings of the bulb but the timing of the surge currents are a typically few milli seconds
(mil stan 1250) while the blade fuze blows in 100s of milli secs.
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dnmalc
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| posted on 26/5/10 at 12:28 PM |
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Stot
I am planning to use the sierra stalks but i am trying to reduce the number of relays and fuzes in the sierra fuze box hence the concernts about the
number of fuzes and relays. I am surprised about your comments about the rating of the column switches as uncle henry does not use thing like relays
if he can get a way without. But hey that simplifies the electrics even more and I can start of will lower rating s on the fuze and work up to a
situation where it does not blow.
Thanks everyone for the input.
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coozer
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| posted on 26/5/10 at 12:56 PM |
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The idea of all individual fuses is if one goes off you still have the other side on. That's why side lights are fused right and left so if one
fuse blows you still have alight showing on one side.
1972 V8 Jago
1980 Z750
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Stott
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| posted on 26/5/10 at 03:07 PM |
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On my diagrams up to 1987 the white wire from 56a on the column switches goes via F14&F15 straight to the main beam filaments, no relay.
For 1987 to 1990 however, the brown/yellow wire from 56a on the column feeds the coil(85) of a main beam relay, which then feeds out via F1&F2 to
the main beam filaments on a white wire.
So it depends which Sierra you're breaking, the earlier ones had the rated column switch (mine) the later ones it would seem run a relay (which
you will have to use if that's what you've got)
HTH
Stott
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