Ignition light came on...

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Ken Davies
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Ignition light came on...

Post by Ken Davies » Tue Feb 13, 2018 10:47 am

HI, auto electrics are going to be a steep learning curve for me and here's my second test after a simple indicator earth at the weekend. Driving down the M3 this morning all was well then the ignition light came on and the voltmeter dropped to zero. The only other symptom I'm aware of is that the indicators were not indicating - the 'trafficator' light would come on but not flash. I've left her at home and gone to work in the boring but reliable Volvo but would like to sort this asap, what would be your areas of suspicion please?
Thanks :)


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Ignition light came on...

Post by Old and Slow » Tue Feb 13, 2018 11:11 am

Possibly an earth issue on the wiring from the voltmeter and the flasher can?


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Ignition light came on...

Post by philhoward » Tue Feb 13, 2018 12:40 pm

No earth on the can as standard.

Ignition light on and voltmeter dropping to zero (what about the other gauges?) sounds like losing the feed from the ignition switch to be honest?

Voltmeter dropping to 11V looks like it's dropped to zero, but could be either the fan belt has failed, or the alternator has actually failed - both would drop the voltage to the point the indicators wouldn't work correctly and give those symptoms.

Lack of fan belt means the water pump isn't running either..


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Ignition light came on...

Post by Roger Pennington » Tue Feb 13, 2018 12:49 pm

Yes, Phil beat me to it, but I was just going to say the first thing I would do if the ignition light came on is stop ASAP to check the fanbelt, because if that fails you lose the water pump drive and the car will quickly boil. If the car didn't boil, then it probably wasn't that, so I'd agree with Phil's other suggestions.


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Ignition light came on...

Post by Ken Davies » Tue Feb 13, 2018 12:59 pm

Hi Everyone,
Thanks for your replies; the first thing I did was watch the temperature gauge and was very happy that stayed just where I wanted it. Only the voltmeter dropped, everything else kept working and if it is indicative of anything the headlights were working and bright when I got home and the fan belt was in place. Can anyone point me to a beginners guide to auto electrics suitable for our cars or give me a primer on testing the alternator and 'feed to the ignition switch'? I have the necessary electrical test equipment if not the knowledge of how to use it effectively!
Ken


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Ignition light came on...

Post by halfpenny » Tue Feb 13, 2018 1:08 pm

I had voltmeter drop to zero last week on my 5a - no other fault. Pulled the dash top out, and fiddled with connections, and now working again. Don't know where the problem was, and couldn't reproduce the fault, but happy now.



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Ignition light came on...

Post by philhoward » Tue Feb 13, 2018 1:11 pm

Check the battery voltage with everything off, ignition on, and then with the engine running.

Should be something like 12.6V, 12.5V and 13.5-14.5V.

Check the state of the plug in the back of the alternator as well - both it’s security and give the wires a gentle tug to make sure they’re not loose.

If you pull the plug to the alternator, the large spade terminal should have battery voltage on it, the small spade terminal should have nothing until the ignition is switched on (don’t start the engine), then battery voltage.

I’m not sure it would have been the ignition switch thinking about it as you would have had more symptoms.


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Ignition light came on...

Post by Roger Pennington » Tue Feb 13, 2018 3:17 pm

I'm afraid I can't suggest a general guide to electrics, as it's not really my speciality either, however one thing that is definitely useful if you haven't found them yet, are Peter Freeman's downloadable colour wiring diagrams, on this link.


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Ignition light came on...

Post by Ken Davies » Thu Feb 15, 2018 7:43 pm

OK, alternator off and the lead to the ignition has a break in the insulation along with clear signs of arcing across to the alternator. Hoping that’s the problem...
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Ignition light came on...

Post by philhoward » Thu Feb 15, 2018 8:25 pm

That’s not good - probably fried the diode pack :(


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Ignition light came on...

Post by Ken Davies » Thu Feb 15, 2018 8:54 pm

Phil, I’m really appreciating you taking time to look at this. It’s a quick fix to remake the connection but if it has “fried the diode pack” (which I’ll Google later) is that a new voltage regulator or a whole new alternator?


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Ignition light came on...

Post by philhoward » Thu Feb 15, 2018 8:59 pm

A replacement regulator/diode pack is probably close to the cost of a new alternator to be honest.

It doesn’t look like a 17ACR at a glance - has it been upgraded to an A127 per chance?


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Ignition light came on...

Post by Ken Davies » Thu Feb 15, 2018 9:08 pm

I have receipts and notes going back to 1978 but nothing for an alternator (I’ve only had her for 3 weeks) although it looks brand new. Tomorrow I’ll study it for marks, what difference does it make?


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Ken Davies
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Ignition light came on...

Post by Ken Davies » Fri Feb 16, 2018 7:43 pm

Pleased to report that remaking the connection was all that was needed. I was very surprised to find how close the alternator is to the brake servo once tensioned. Is that normal or time for a new belt?


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