Key switch wire. Difference between IG1 & IG2

[Mgrene]

I’m about to install gauges which of course shall turn on when you turn on the ignition.

But when I look at the wire diagram, there is apparently two wires. One for ignition 1 and one for igntion 2.

Which one should i chose and why is there two?

 

 

 

 

[jagman]

ign 1, the ign 2 is kept on during cranking the engine and provides the ignition and fuel and ECU - This prioritises these during cranking as the voltage drops from the battery to ensure engine starts

the ign 1 is removed during cranking and returns after engine start ( switch returns to ign1)

the ign 1 are not required to start the engine a lesser priority during low volts situations

[Mgrene]

So which one do you suggest I use for gauges etc?

 

 

 

[Mgrene]

Now I think twice, it was actually a stupid question. I should use IG1 since IG2 only will be on for s short period.

 

Edit. Also see now that you suggest IG1

 

Thanks mate.

 

 

[jagman]

Ign 1

This is for all other circuits not needed to start the engine

[Mgrene]

Final question.

How about ACC ? Can that also be used?

 

 

 

[jagman]

ACC is for accessories- things you want to have switched on without having the ignition on , saving the battery being drained over longer periods , so it powers the radio allowing you to listen when parked up , or have a smoke (cigar lighter - high load but only for a short time)

So no , unless you are into looking at your gauges while nothing else is running - lol

[Mgrene]

Jagman you are a star. Thumbs up.

 

 

 

[jagman]

Just for completeness and an overview :

Some circuits are directly fed bypassing the ignition altogether- this allows these to operate without needing your keys , usually horn , so you can beep your mate without fumbling for keys , the headlight flash for similar reasons and hazards , these are very short term loads , sometimes the heater fans work , to allow passenger cooling or heating if the driver has left the car with the keys .

This also has the effect of reducing the current that passes through the ignition switch - the more current passing through an ignition contact , the more likely it will fail , another reason for multiple switch contacts.

Adding any electrical items requires some thought as to where you draw the power from , usually this never happens and some of the most random wiring installs are the result - a total nightmare for the next owner , especially when it goes wrong ......17 different circuits all fed from the cigar lighter - lol

[Mgrene]

Will the ACC also be shut down while IG2 is cranking the engine?

 

 

 

[Mgrene]

And will there be no power going through IG2 & ST1 as soon as the key returns to IG1 ?

 

 

 

[jagman]

The diagram represents the switch sequence - first click is ACC - this is powered , the second click powers ign 1 as well , at the same time ign2 is powered , the next click is sprung loaded to start - at the same time ign 1 and ACC is opened and ign 2 remains closed

After start you release the switch and all 3 are now powered - until you turn back to off or ACC .

This is why ignition switches have some length to them , the contacts are along a shaft so contacts can be operated at the same time by some cam or key way on the barrel shaft all turned by the key .

And why you can get some weird problems when an ignition switch contacts go bad or worse intermittent , key barrels worn etc .

All normal car stereos are around 45-50 watts for example - this is not because manufacturers can make more powerful amps , but car wiring is rated to a max current that gives 45-50 watts - bigger amps could bugger the wiring and ignition switch ACC contacts .

Hence mahoosive aftermarket amplifiers run direct off a battery lead .

Aftermarket things fitted , we all have them , need some thought , how much load and current , and things like start current on rad fans or motors etc - you can't just hook them up to any nearby powered wire just because it's handy - lol

I've seen so many cars with high quality mechanicals and cosmetic installs with shockingly bad wiring installs - I always try and imagine their Xmas tree light installs at home - 7 extension reels all loaded with plugs !!!!