Ford Focus - Focus alternator problem

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Mon 28 Jun 2010 11:25
Ford Focus - Focus alternator problem - Jamesey

I have a strange problem which appears to be with the alternator. Car is Focus 1.8 TDCi 2006, 117k miles.

Symptoms and observations
- whining noise on tickover, pitch moves with engine speed.
- alternator casing gets very hot soon after starting engine from cold (within 1 minute)
- battery voltage is around 12.5v with ignition off, around 11.5v when engine running
- car appears to drive and operate fine including air-con, power steering, etc, and battery warning light goes out after starting engine.

Initially I thought the alternator was mechanically broken e.g. something was rubbing inside hence the whining noise and heat. However, when I removed the 3-wire connector from the alternator, the noise stopped, the alternator stayed cold, and the battery warning light came on.

The whining noise did not develop over time, it just started one day, although not sure of the exact time. I've done a resistance check between the +terminal of battery and the alternator terminal and that seems fine.

I've read stuff which indicates it might be a fault with one of the three 'control' wires? How much would it cost to get the wiring replaced to eliminate this?

One post said a whining and overheating alternator might suggest "the battery had a poor coupling" but I don't know what this means!

I've read about multiple alternator failures and I'm wanting to avoid this - my car is out of warranty!

Any advice appreciated.

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Mon 28 Jun 2010 12:09
Ford Focus - Focus alternator problem - Peter D

You may have a faulty diode pack and the output form the alternator is not DC. Or the regulator is duff. But the heat and onlt 11.5 volts out points more to the doide pack. You need a scope to see the waveform. Regards Peter

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Mon 28 Jun 2010 12:37
Ford Focus - Focus alternator problem - Ben 10

Fords have had problems with the alternators on the MK2. Get it checked to make sure its that, and replace ASAP.

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Mon 28 Jun 2010 13:15
Ford Focus - Focus alternator problem - Jamesey

You may have a faulty diode pack and the output form the alternator is not DC. Or the regulator is duff. But the heat and onlt 11.5 volts out points more to the doide pack. You need a scope to see the waveform. Regards Peter

Thanks for this. If I'm checking the voltage/waveform, where should I do it, on the power output point? I assumed the 11.5v is just the battery voltage while its under load for running the engine?

Should I disconnect the power wire which goes to the battery first? And if it were the diode pack or regulator, are these part of the alternator or separate?

I checked the voltage on the 3 pins on the alternator (having removed the connector hence stopping the noise/heat) and one was 0, the other two both came up at about 4.5v using DC mode on voltmeter, and 8.5v on AC mode.

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Mon 28 Jun 2010 17:40
Ford Focus - Focus alternator problem - Jamesey

An update - spoken to an auto electrical specialist, he's pretty sure it's the diodes gone, apparently a common problem with the Denso alternator on later Focus models. He reckons he can replace the diodes (with higher rated ones) for about £140 inclusive, I'll be happy with that if so.

Thanks for the earlier replies on this. If I have further problems I'll post them here!

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