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Which circuits require relays...
CosKev3 - 22/10/14 at 10:41 PM

As above, starting to plan my loom/fuse box area and wondering how many relays I will need to make space for?

Just main loom item's btw, not engine related ones

Cheers.

Smoking Frog - 23/10/14 at 07:54 AM

Maybe I used more than was necessary as I ended up with eight, six were non engine related.
Fog light
Fan
Horn
High beam
Low beam
And one for the stalk pin 56 earth.

twybrow - 23/10/14 at 12:14 PM

quote:
Originally posted by Smoking Frog
Maybe I used more than was necessary as I ended up with eight, six were non engine related.
Fog light
Fan
Horn
High beam
Low beam
And one for the stalk pin 56 earth.


Indicators also use a relay. Fuel pump as well, but you may be including that within your engine loom.

luke2152 - 23/10/14 at 12:15 PM

Most OEM's don't use relays on any of these except the fan so they are not really needed.

*Fan will need one if you're switching it from ECU.
*Headlights will perform a bit brighter if switched from a relay but it needs to be near the headlight as using a long run of heavy wire would defeats. Also you can use one 5 pin relay for both Hi/Dip.
*Fog relay unnecessary unless you have front fog lamps.

But I'd suggest one extra relay that comes on with the key to switch power to the fuse box to power all the little things so as to not put much current through the ign switch

CosKev3 - 23/10/14 at 12:45 PM

Cheers so far

quote:
Originally posted by twybrow
Indicators also use a relay. Fuel pump as well, but you may be including that within your engine loom.


Yeah pump relay is built in with engine loom.
Indicators just need a flasher relay?


quote:
Originally posted by luke2152
Most OEM's don't use relays on any of these except the fan so they are not really needed.

*Fan will need one if you're switching it from ECU.
*Headlights will perform a bit brighter if switched from a relay but it needs to be near the headlight as using a long run of heavy wire would defeats. Also you can use one 5 pin relay for both Hi/Dip.
*Fog relay unnecessary unless you have front fog lamps.

But I'd suggest one extra relay that comes on with the key to switch power to the fuse box to power all the little things so as to not put much current through the ign switch


Using sierra stalks,so I thought a relay was required for headlights?

Good info on the 5 pin relay,will save a bit of space

[Edited on 23/10/14 by CosKev3]

luke2152 - 23/10/14 at 12:56 PM

I know nothing of sierra stalks so you could be right

CosKev3 - 23/10/14 at 01:21 PM

quote:
Originally posted by luke2152
I know nothing of sierra stalks so you could be right


They switch the earth to headlights.

The 5 pin relay would be a 'double output' one?

coozer - 23/10/14 at 01:28 PM

Main ignition relay.
For the sierra switch gear one for each main and head circuit.
One down next to the fan on the always live circuit.
Both live and switched circuits fused at the battery terminal .

As said one for the fuel pump on the ecu circuit.

Everything else fused whether on the always live or switched circuit.

[Edited on 23/10/14 by coozer]

luke2152 - 23/10/14 at 01:29 PM

quote:
Originally posted by CosKev3
quote:
Originally posted by luke2152
I know nothing of sierra stalks so you could be right


They switch the earth to headlights.

The 5 pin relay would be a 'double output' one?


Well you have a normally open pin and a normally closed pin on the relay. Normally open for hi normally closed for dip.

luke2152 - 23/10/14 at 01:40 PM

Like this
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.jpg

30 = 12v from the headlight switch
87 = Hi
87a = Lo
85 = 12v from the headlight switch
86 = switched ground from the high beam stalk

But do test it first in case I'm mistaken

[Edited on 23/10/14 by luke2152]

coozer - 23/10/14 at 03:01 PM

Thing is the sierra headlight switch is live from the relay switched earth...

luke2152 - 23/10/14 at 04:55 PM

consider it an example and adjust as necessary - I'm not familiar with sierra switchgear

snowy2 - 23/10/14 at 08:16 PM

need = ....none. (if you use the right switches)
you could use for some to enable you to use light weight switches....... my kit car has something like 11 relays. it does make earth switched consumers easier to control. it also keeps heavy wire runs very short. (therefor cheaper to wire up)
you can also use relays for conditional switches (fog lights for example)