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starter motor relay...yes or no.
Jenko - 28/6/17 at 07:19 AM

Trying to make sense of the westfield loom, and there is no provision for a starter motor relay. Clearly I can fit one in, but the question is...is it really needed?. I did fit one on my last build, but westfield don't seem to have one...Is it needed / desirable?.



[Edited on 28/6/17 by Jenko]

Quinten - 28/6/17 at 07:24 AM

Not needed, but good practice (imho). There is not much current required to activate the starter.

chris - 28/6/17 at 07:43 AM

isnt the solenoid doing the same job as a relay

rusty nuts - 28/6/17 at 07:49 AM

The starter motor solonoid is a relay but it may draw a higher current than the ignition switch can cope with? Fitting a relay would reduce the load on the switch so might be good practice . Did the ignition switch donor originally use a relay? If so I would fit one.

peter030371 - 28/6/17 at 07:55 AM

What starter switch are you using and what is it rated too?

Jenko - 28/6/17 at 08:48 AM

It uses the standard switch that comes with the westfield kit and also the westfield loom. westfield obviously don't think its needed, but I wondered if it's worth doing anyway.....I can't remember if my last westfield had one!.

peter030371 - 28/6/17 at 10:06 AM

quote:
Originally posted by Jenko
It uses the standard switch that comes with the westfield kit and also the westfield loom. westfield obviously don't think its needed, but I wondered if it's worth doing anyway.....I can't remember if my last westfield had one!.


If Westfield don't use it then I would not add it, just one more thing to go wrong and more connections which are always the week point of a loom!

big_wasa - 28/6/17 at 10:37 AM

The solenoid draws around 10a after the initial spike so it depends on the switch gear. If its a Sierra ignition switch its not needed but I would use one to pre long it's life as there not as easy to find.

Ford have used a relay as standard since 1995 ish as a way of the ecu immobilizing the starter.

[Edited on 28/6/17 by big_wasa]

britishtrident - 28/6/17 at 10:47 AM

Proper tintop ignition switches are designed wth wiping contacts to better withstand the arcing as the switches makes and breaks.

If you do use a relay use a big one as the coils on pre-enagage starter solenoids draw a huge in-rush current just to operate the solenoid, this is the solenoid on a Denso, the solenoid Lucas Pinto draws about the same inital peak 35 amps . Old style starter solenoids drew much less, Rolls-Royce on the old V8 used a Lucas BL Mini starter solenoid as a relay to operated the pre-engage starter solenoid.