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Author: Subject: Dead ignition switch?
pekwah1

posted on 14/10/14 at 05:51 PM Reply With Quote
Dead ignition switch?

Hi guys,

For some reason I have no power...

Getting 12v from the battery and at the starter.


Checking my ignition switch (std ford 4 pole switch), I get 12v on the supply with the switch off, but when I turn the ignition switch on, it drops to around 2v.

I haven't changed anything wiring wise lately, just wondering if it's likely to be a short somewhere, or maybe if the ignition switch itself may have somehow died?

Any opinions welcome!

Cheers
Andy

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britishtrident

posted on 14/10/14 at 06:06 PM Reply With Quote
A dead short should still show more than 2volts, check the battery terminals are clean and tight.
What voltage to you get with the only the side lights on?
A fully charged battery should show at least 12.5 volts with no load.





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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pekwah1

posted on 14/10/14 at 08:24 PM Reply With Quote
As above I'm getting 12v at the battery and the starter.

Supply to ignition gives 12v until I turn the ignition on when it drops to 2v ish.
Can't check lights or anything else as there isn't enough voltage to power anything

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britishtrident

posted on 14/10/14 at 08:52 PM Reply With Quote
Clean and check the battery terminals.
If no joy disconnect battery and charge, but it looks to me more like a bad connections
You should be measuring the voltage across the battery terminals directly





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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pekwah1

posted on 14/10/14 at 09:02 PM Reply With Quote
Maybe I'm not talking English here?

I have checked the battery at the teminals.
It is 12v

My problem is at the ignition switch. Supply coming to the switch is definitely 12v, but when I turn the ignition on, everything drops to 2v.
Problem with the switch or a short somewhere?

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britishtrident

posted on 15/10/14 at 07:50 AM Reply With Quote
The voltage needs to be checked with the DMM probes touching the actual post of the battery not the connector that clamps on to it. The reason for doing it this is the one most likely sources of this type of problem is a high resistance in connection to the battery itself.


If it is not that it points to a battery issue, the battery would need to be charged to somewhere between 12.5 to 12.8 volts (measured off charge) , then rested for at least 20 minutes then tested.

When not in use batteries should be charged every month to maintain at least 12.4 volts off charge with no load.
Modern enhanced chemistry batteries are easily damaged if they are discharged below 11.5v and most modern batteries will not accept charge if completely flattened.

A lead acid battery with no loads on it will still show about 10.5 v even when completely flat but put a even a small current load on it and voltage will drop to close to zero. A battery with a decent amount of charge will show 12.3 to 12.7 volts.

A healthy battery with a decent charge will still show 9 to 10.5 v with an almost dead short across it drawing 200 to 400 amps.

A healthy battery with a very low charge under the same load would show about 8 v which slowly drop.

A battery with a dead cell (aka "gassing" cell) would show about 6 v under very heavy current draw.





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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adithorp

posted on 15/10/14 at 11:43 AM Reply With Quote
Are you sure the battery isn't just flat?





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coozer

posted on 15/10/14 at 02:54 PM Reply With Quote
I had a problem like this, battery seemed fine vin isolation but apply a load it dropped out.

After much head scratching it turned out the battery had a short that only reared its head when a load was applied.

I'd get the battery checked but first check the ignition switch for shorts, simple continuity check to earth through all the wires, in all positions.





1972 V8 Jago

1980 Z750

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pekwah1

posted on 15/10/14 at 04:07 PM Reply With Quote
Hi Guys,

Right, it's not the battery.
Battery tested (disconnected) is 12.6v, this doesn't change with the ignition on.

This is a simple drawing of my ignition electrics:



The poles with "2v" marked on them only read this once i have turned the ignition switch on. With the ignition switch on, the battery still reads 12v as does the first pole of the kill switch.

Testing the ignition switch itself, with the switch in the "off" position, i can earth the battery on the supply pole. With the ignition on, i am reading 2v.

This is starting to look like i've earthed a live somewhere, or maybe live'd an earth?
Only other thing i can think is that i have a bad earth and it is essentially earthing through the easiest path (live wire)?

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whitestu

posted on 15/10/14 at 04:19 PM Reply With Quote
That suggests an issue with the kill switch? Can you test it?

If you had earthed a live straight from the battery you would be seeing some smoke by now!

Stu

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pekwah1

posted on 15/10/14 at 04:24 PM Reply With Quote
sorry forgot to say that with the ignition switch off, the kill switch reads 12v on both poles also...
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cliftyhanger

posted on 15/10/14 at 04:29 PM Reply With Quote
Sounds like a bad connection. They will carry Voltage (sorry, I know you don't really carry voltage...) but when a current is drawn the voltage drops to near zero.
Double cheack all connections, especially that kill switch. Or even bypass the kill switch. It looks like it is the issue.

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pekwah1

posted on 15/10/14 at 04:30 PM Reply With Quote
i was thinking a bad connection somewhere...
I'll bypass the kill switch (although had tried crossing the terminals at the rear which didn't make any difference....)

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britishtrident

posted on 15/10/14 at 04:46 PM Reply With Quote
No load voltage on a battery only indicates the state of charge, you need to measure the voltage when it is under load to get an idea if the battery is OK.





[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]

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coozer

posted on 15/10/14 at 05:01 PM Reply With Quote
The diagram there shows that's the starter circuit?

If so the obviuos culprit there is the starter solenoid... What's the continuity like between the wire and earth?





1972 V8 Jago

1980 Z750

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cliftyhanger

posted on 15/10/14 at 05:35 PM Reply With Quote
Good point. Turn all the light son and see what the battery voltage does. It it plummets you know where the problem lays.

Talking to a forklift engineer, he hates the modern battery testers, much prefers the old fashioned drop testers......Modern peeps probably too scared to use them.

What did you use to try bypassing the switch? All connections need to be good and robust to carry decent current. You should be able to use just one terminal as a joint. Good and tight though.

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pekwah1

posted on 17/10/14 at 11:24 AM Reply With Quote
sorry got this slightly wrong.
i get 12v on both terminals of the kill switch (i bypassed to check anyway so it's definitely not this.

Lights do nothing, but then i'm not getting enough voltage to do anything from the ignition.

I have narrowed this down to the ignition live on the ignition switch.
As soon as this cable is connected with the ignition is on, i am reading 12v on the terminal and other live cables in the car.

Testing across the battery at this stage still returns 12.6v, same on the kill switch. It's from the ignition switch onwards that i lose the voltage.

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02GF74

posted on 22/10/14 at 08:00 AM Reply With Quote
Ignition switch is in position 1?
Measuring voltage you have black lead on the same earth eg battery neg terminal.
Does the ignition switch or wires near it feel hot.

To drop 10 v with a good fully charged battery would need a large current to be drawn with something getting quite hot.






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