Ford Fiesta 1.3 (1995) - Power Failure in Ford Fiesta

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Wed 9 Jan 2013 09:28
Ford Fiesta 1.3 (1995) - Power Failure in Ford Fiesta - Regal88

Hi

I recently broke down due to power failure in the car. The AA mechanic suspected the brushes in my alternator had gone. I have had a brand new alternator and battery fitted. Last night whilst driving home, the car started to show signs of power failure again. My wiper blades slowed down, headlights dimmed and the radio switched off.

What other issues can cause power failure as I am confident it is neither the alternator or the battery.

A friend of mine says that I may have a problem with the Earth wire?

As you can probably tell I am not clued up on car mechanics so any advice would be great.

I am putting this question out here first rather than taking the car to a garage to see if I can get an idea of what I am dealing with and potential cost to repair as money is a bit tight; so would have to weigh up whether the car is worth keeping depending on cost to repair.

Cheers
Sam

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Wed 9 Jan 2013 09:35
Ford Fiesta 1.3 (1995) - Power Failure in Ford Fiesta - Peter.N.

Firstly connect a voltmeter across the battery, it should read about 14.4 volts with the engine running, if it does the alternator is charging OK, if not either the alternator is faulty or you have a poor connection somewhere.

The earth connection your friend is referring to is probably the one from battery negative to the engine/gearbox.

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Wed 9 Jan 2013 10:13
Ford Fiesta 1.3 (1995) - Power Failure in Ford Fiesta - Regal88

Thanks for your reply Peter.

If the earth connection was faulty would this cause the cars power to fail?

Also, would the voltmeter not read about 14.4 volts only if the alternator was faulty?

I ask this because both the alternator and battery are brand new so I thought that if a voltmeter was showing around 14.4 volts with the engine running, then I shouldn't be losing pwer as I drive around?

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Wed 9 Jan 2013 16:24
Ford Fiesta 1.3 (1995) - Power Failure in Ford Fiesta - Peter.N.

If you have 14.4v on the battery it means that the battery is connected to the alternator but not necessaraly to the rest of the car effectively. A faulty earth may affect the charge rate but if you have a poor connection it will normally show up when you try to start the car as the starter draws several hundred amps.

Connect the meter between the negative battery connection and a good clean earth connection on the engine, there should be little or no voltage present, check again while someone operates the starter, there will be a small voltage but it shouldn't exceed about 0.5 v, if it does by much you have a poor earth connection.

When your battery appears to be discharged, again check the voltage across it, it should be a little over 12 volts, below 12v and its flat. If you have a poor connection it maybe that the battery is OK but the power is not reaching the starter.

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Wed 9 Jan 2013 16:54
Ford Fiesta 1.3 (1995) - Power Failure in Ford Fiesta - skidpan

A 12 volt battery is not 12 volts, its actually 12.6 volts. But even a battery that holds 12.6 volts will not necessarily start a car if the plates are b*****ed or there is a calcium build up in the bottom, been there, done that. It can sometimes supply the volts but not the current required.

By putting a volt meter across the battery with a running engine all you are getting is the output voltage pf the alternator. This should be between 14.2 and 14.4 in a modern car although cars with stop/start and the special batteries can (and do) charge with a slightly higher voltage. Thus even with a totally duff battery you would still see the alternator voltage.

Same applies to the battery earth, the volt meter test proves nothing.

By all means check the voltages but clean up the battery terminals (and put a little vaseline on then before reassembling) and check the earth cable contacts to the engine and body.

Have you checked the the alternator belt is tight.

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