Hi guys

My shiny new start button and ignition key switch have come from Premier Wiring to replace my standard Sierra ignition Key switch. This is the first stage of moving all of the Sierra column switch gear onto my dash.

Now I must admit that car electrics leave me cold. I've just spent about an hour looking at the diagrams in the Haynes manual and lets just say I'm scratching my head at what I need to do!

What I think I have found out (and please correct me if I'm wrong) is the following:

On the Sierra key switch I have the following wires which I believe are these

Yellow "R" accessories/radio not required
black/blue "50" Start
Red "30" Live
Yellow/Black "15" Ignition

Now my new key switch is just an on/off switch so the start button will take over the ignition bit, this is where it all gets a bit confusing for me Now I've had a go at drawing a little diagram as to what I think it should be wired like which I've attached below. Is this anywhere near correct? As obviously I'd like to avoid setting my wiring on fire if at all possible

And please no one laugh at my diagram OK!

You will probably want to run your push button start via a 4 blade relay. Take a switched feed from your loom to pin 30 & 85 of the relay. Connect the low voltage side pin 86 via your start button to earth, and pin 87 (high voltage) to your starter - probably a white / red wire.

relay diagrams

So is that the old switch in your diagram or the new if its the new I'd put your button on the Ign side otherwise your switch feed is permanently live whereas you want to feed it when you switch on igition. As paul says put a relay between to reduce current on the switch.

Cheers,
Bob

[Edited on 12/8/08 by splitrivet]

I will have a think about this tonight and get my wiring diagrams out.

If you wire it as per your drawing it is possible to turn the starter motor whilst the engine is running and this is a bad thing.

Why do I need a relay? I'm just replacing the Sierra key switch with an on/off key switch and momentary switch. The chap at Premier wiring said they were both up to the job?

Can't you accidentally turn the key in a normal car when the engine in running then?

Cheers

Dave

quote:

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Originally posted by orbital
Why do I need a relay? I'm just replacing the Sierra key switch with an on/off key switch and momentary switch. The chap at Premier wiring said they were both up to the job?

Can't you accidentally turn the key in a normal car when the engine in running then?

Cheers

Dave

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Hi Paul,

The new key switch has three connectors on it (the diagram above has the new key switch in it).

To deal with the chance of the button getting pressed while the engine is running, is that what people have a another switch for? with the doomsday cover over it? (or whatever it's called ) Like this:

I wouldnt bother in a car like a locost your going to know if the engines running or not.
Cheers,
Bob

Good point well made Bob

Cheers

Dave

So you have the On-Off-Ign switch (£10) from Premier like the one a third of the way down??

http://www.premierwiring.co.uk/index.php?module=Website&action=Text&content=1133393725973-8435&parentContent=1133392767901-3830

If so and you have a momentary switch for your starter, then just run the two connections and ignore the starter position there. Take a switched feed to your starter button. The toggle switch you show with 3 connections will probably allow you to either momentarily give a connection or cut the connection so try it with a continuity meter to see what happens




[Edited on 12/8/08 by Paul TigerB6]

Bob do you mean like this?




Paul the key switch just clicks once, just off then on and thats it I think. I haven't got a continuity tester or anything like that to test it (not that I'd know what do with one anyway! )

Thanks a lot

Dave

I just use a really basic multimeter for most of my electrics - cost me about £5 off ebay!! Even the most basic meter will be a huge help for jobs like this and will show you what the connections on your new switches do

cheapo meter

So how do you test your electrics then, or is it just trial and error??

[Edited on 12/8/08 by Paul TigerB6]

The car was pretty much complete when I bought it, so I haven't done anything like this before It's quite a learning curve!

Cheers

Dave

Definately worth getting a simple multimeter then if you dont have one - i'd say its pretty much an essential piece of kit.

You will find it so much easier to do loads of jobs with one. Really easy to check circuits with a continuity meter even if its working out what wire is what in the loom and switches make so much more sense if you can see what happens when you move the switch position

No you dont need the connection on 50 the side of the switch that goes to 50 take that straight to the starter motor less connections means less to go wrong.
Cheers,
Bob

Right I'll do that Paul and cheers Bob I get what you and Paul mean now about the 50 side of things. Just one more thing. What sort of cable is best for this job? what rating would be best?

Thanks again

Dave

quote:

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Originally posted by orbital Just one more thing. What sort of cable is best for this job? what rating would be best?

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Depends on current draw, length of run etc but I would think 3mm 44/0.30 which is rated 27.5 Amp would be more that ample.
Cheers,
Bob

Cheers guys, time to have a dabble!!

Dave

Fair comment but its easier to catch a button acccidentally than to turn an ignition key. And on more modern cars there is a mechanical device within the ignition switch to stop this ie when the key is turned to the strart position and returns to the ign position it is prevented from being turned to the start pos again until the key is turned to the off position. I know cos this is the case in my daily driver.

Was only trying to be helpful

quote:

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Originally posted by orbital

Can't you accidentally turn the key in a normal car when the engine in running then?

Cheers

Dave

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