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Relays - which circuits?
eddymcclements - 25/2/03 at 10:32 AM

Just a question - which circuits are commonly switched by relays? Obviously those that draw a fairly high current, so I'm thinking of the following:-

headlamps
fan
horn
starter solenoid(?)

Anything else? Are people splitting the headlamps L and R so that there's no single point of failure?

Cheers,

Eddy

jonti - 25/2/03 at 11:52 AM

You shouldnt need a seperate relay for the starter. The pick circuit on the motor solly don't draw much. Make sure the heavy cable goes straight to the battery though !!!!

You'll need sollys for headlights if you're using the later seirra column switches.

Fan , if auto and u use the right cable and fuse shouldnt need one.

Horn, unless you're using heavy duty ( ie air horns etc ) shouldn't need one either.

All the above assume correct fusing and cable obviously !!!

Northy - 25/2/03 at 07:00 PM

Which Sierra column switches allow you to use headlights without relays? How do you identify them?

Thanks

jonti - 26/2/03 at 06:42 PM

quote:
Originally posted by Northy
Which Sierra column switches allow you to use headlights without relays? How do you identify them?

Thanks


Not sure mate but I believe most do need a relay. I would think the only way to ID 'em would be to check the fuse box for lack or not of relays. Relays are P** easy to wire in and they keep the heavy juice out of the cockpit so I'd use one anyway for H/lights. Wouldn't have thought there was any need to split L and R just use one 30A with seperate NO and NC contacts for main and dip.I haven't looked yet but there must be one in the old sierra fuse box lying under my bench which I shall no doubt be using.

[Edited on 26/2/03 by jonti]

[Edited on 26/2/03 by jonti]

Mark Allanson - 26/2/03 at 07:01 PM

The starter solenoid is effectively a relay, just a bloody big one

[Edited on 26/2/03 by Mark Allanson]

paulf - 26/2/03 at 09:55 PM

The early sierras had no relays , my switches came from a mk 1 sierra and I am using them on there own. They appear to be the same as some Mk 3 escort switches i also have.
If you check the wiring diagrams in a haynes manual it will be easy to tell for certain.
Paul.

quote:
Originally posted by Northy
Which Sierra column switches allow you to use headlights without relays? How do you identify them?

Thanks

jonti - 27/2/03 at 01:59 PM

quote:

If you check the wiring diagrams in a haynes manual it will be easy to tell for certain.
Paul.


I take your point Paul, but I've never found anything "easy to tell" from a Haynes Manual wring diagram ! Half the battle with Haynes is deciding which diagram applies to your particular car !!

[Edited on 27/2/03 by jonti]

Peteff - 27/2/03 at 08:55 PM

According to my manual all sierra columns switch the headlight relays on the earth cable, that's how I wired mine and they work o.k.

yours, Pete

MB - 28/2/03 at 09:08 PM

The circuits best switched by relays are the ones that take a high current.

Things like head lights / full beam, fog lights, horn, wipers, etc.

If you don't use relays you will end up with pitted contacts in your switches and eventually they will fail.

For additional safety and long life electrics you can also get diode protected relays...