Battery Mster Switch...Whats it For ?

[Bafty Crastard]

A dim question you ask !

 

I am nearing the completion of new motor and have just completed the wiring arrangement in the engine bay as follows:

 

Connected to the positive battery terminal

 

1) Red wire to the battery master switch

2) Single brown wire

3) Two brown wires joined together

 

Connected to the negative battery terminal

 

4) Earth to engine "strap"

5) Single black (?) car loom wire

 

Using this arrangement only kills the supply to the starter motor, the other electrical systems on the car remain live ! Is this the point of the master switch ? A quick phone call to Mr Caterham for confirmation...."Yes that’s right".

 

After a couple of hours thinking I am not happy, surely a battery master switch should kill all electric's on the car....A second call to Mr Caterham..."fit the single and double brown wire to the starter motor then all electrical systems are dead"....that sounds better, but the wires won't reach !

 

Can any person tell me the correct way of connecting the battery master switch to be affective, I mean if you may have a small wire fire on the car, then you'd want to kill all the electric's, right ? also what effect this will have on some electrical systems if the supply is terminated, ECU, immobilliser and the like

 

Any thoughts please

 

 

Edited by - Bafty Crastard on 16 Dec 2002 13:40:46

[Casbar]

Don't know about K's but on my xflow the battery master switch kills everything, including all the electrics.

 

Possibly the immob needs current all the time, don't know, cause I don't have one

[philwaters]

When I wired mine I took a single big red wire to one side of the MS and then ran the browns and the starters big red wire to the other side of the switch... Hey presto, my car dies when switch off. Oh and fitted the resistor and earth wires of course.

This may be something to do with not wanting to loose power to yor ECU, otherwise you have to re-program it with throttle position on the K's don't you? Kind of defeats the object though.

p.s agree, also to do with immobiliser - my Vecta doesn't care if you disconnect it, but a key fob type might.

Phil Waters

You mean you can drive these?

I thought it was just there to polish 😬

 

Edited by - philwaters on 16 Dec 2002 13:27:30

[KenEvans]

Strange - I had this very same problem when I buit my car two years ago! It should most definitely kill all electrics. The factory claimed that it had been wired up incorrectly in the factory and they sent me a wiring diagram. I seem to recall the wires reached ok and it work correctly afterwards.

 

Ken

[Andrew_Bailey]

Master switch on mine leaves electrics working but car will not turn over on the starter. I am sure that this is not right and would expect the MS to kill all electrical power other than maybe to the ECU.

[philwaters]

But once the car is running then isn't the only thing keeping it running the power to the ECU? This feeds the Distributor/coil pack and feeds the injectors.. to kill a K ( 😳 ) you would have to cut power to the ECU surely? (don't call me Sirley) A fuel pump cut would be too slow and doesn't prevent sparks igniting spilt fuel anyway...

Has to cut the ECU - but question is does that mess up the immobiliser? If so, then just don't use it unless you REALLY have to ❗

 

Phil Waters

You mean you can drive these?

I thought it was just there to polish 😬

[scooby dooby doo]

if it kills EVERYTHING then stray voltages (eg from the alternator) will potentially kill the ECU.

 

HOOPY 500 kg R706KGU

[philwaters]

Isn't that why you have the resistor though - to take the load from the alternator while it stops spinning?

 

Phil Waters

You mean you can drive these?

I thought it was just there to polish 😬

[Peter Carmichael]

Hoopy,

 

Your comment doesn't follow.

 

The battery is a very useful device for smoothing out the voltage. If you disconnect just the battery then all hell breaks loose. It is a good idea to separately isolate the electronics from any inductive loads if you can achieve it. A correctly wired ballast resistor dumps any stray alternator output when the whole shebang is switched off.

[Trevor Phillips]

For SVA you must have the Hazards available when the Masterswitch is off if that is your anti-theft device. For MSA Blue Book, the Masterswitch must kill everything. The only exception electrically I know of is electrically-fire extinguishers that must not be hard-wired, they run from a PP9 battery.

 

Racing pics and items for sale here

[scooby dooby doo]

I meant to imply that if you just take battery out the system then you may damage things as, as you said, the battery works very well at removing spikes etc.

 

So yes, i enirely agree with you, but my comment didn't really say that ❗

 

HOOPY 500 kg R706KGU