Alternator Problem?

[rusty0273]

I have light staying on intermittently. Battery combined with handbrake and no temperature reading.
This has happened on a couple of occasions. Today I popped into a shop, restarted the car and they've gone out - back to normal. Sounds very similar to an old thread where I believe a new alternator sorted it but mine is intermittent. Any thoughts?

[rusty0273]

The MOT is due in June. Antone know if this is an MOT fail according to the new rules re. dash warning lights?

[rusty0273]

The MOT test now includes a 'Malfunction Indicator Lamp' check. This requires the examiner to visually check that warning lights for electronic stability control, safety restraint systems, anti-lock braking systems and tyre pressure monitoring systems are not permanently illuminated.

[Gaz mr-s]

The alternator rarely gives problems. Check the solidity of the wires in the plug & make sure the terminals are clean.  A spray with wd40 or electrical contact won't go amiss.

[SV-3]

The alternator rarely gives problems. Check the solidity of the wires in the plug & make sure the terminals are clean.  A spray with wd40 or electrical contact won't go amiss.

Check your battery terminals as well.

[Dev]

It could  a bad battery or a bad alternator. I had both at one time or another. The best way to tell if its your alternator is to set a multimeter to measure AC voltage and take a reading at the battery terminals. If the reading exceeds .5 volts AC its a bad alternator.

 To test the battery. With the car off measure the DC voltage across the terminals. The resting voltage should be above 12.5 volts. Turn the headlights on and if the voltage dips below 11.8 volts you have a bad battery.

[rusty0273]

I've checked the battery terminals and I think they are pretty well connected.
I'll get hold of a multimeter and try that as advised. Cheers.

[Carolyn]

I've checked the battery terminals and I think they are pretty well connected.
I'll get hold of a multimeter and try that as advised. Cheers.

Sometimes it pays to take the terminals off the battery, clean inside them and clean (make shiny) the battery posts.

[Alex Knight]

100% alternator.

[shnazzle]

Sounds like when my alternators went.
Been through 2 so far.

Both did the lights thing and if you plug in TorquePro you'll see battery voltage being low and not recovering if you use more.

Eventually you'll end up in a car park in an industrial estate begging at the garage across the road to lend you their battery starter. You'll get it started and on the drive home, voltage will drop below about 9v at which point point your dash lights up. Then at 8v your power steering shuts down.

Good fun..

[1979scotte]

Sounds like when my alternators went.
Been through 2 so far.

Both did the lights thing and if you plug in TorquePro you'll see battery voltage being low and not recovering if you use more.

Eventually you'll end up in a car park in an industrial estate begging at the garage across the road to lend you their battery starter. You'll get it started and on the drive home, voltage will drop below about 9v at which point point your dash lights up. Then at 8v your power steering shuts down.

Good fun..

2 on the same car?
Surely not.

[shnazzle]

Sounds like when my alternators went.
Been through 2 so far.

Both did the lights thing and if you plug in TorquePro you'll see battery voltage being low and not recovering if you use more.

Eventually you'll end up in a car park in an industrial estate begging at the garage across the road to lend you their battery starter. You'll get it started and on the drive home, voltage will drop below about 9v at which point point your dash lights up. Then at 8v your power steering shuts down.

Good fun..

2 on the same car?
Surely not.

Shit luck.

To be fair, the 2nd one was 2nd hand. The one I've got now is new. Ebay special for 41gbp. Works grand. Only downside is I've now got a bit of a supercharger noise.

[rusty0273]

Put a multimeter on it and engine running, the alternator is putting out 14.4V consistently with lights, rear windscreen on. The battery shows around 13V but that doesn't mean its not faulty. Going to get the battery checked at Costco if they do it or Halfords and take it from there.

[shnazzle]

Put a multimeter on it and engine running, the alternator is putting out 14.4V consistently with lights, rear windscreen on. The battery shows around 13V but that doesn't mean its not faulty. Going to get the battery checked at Costco if they do it or Halfords and take it from there.

Tbh that sounds healthy.

[Ardent]

@rusty0273

What does the multi-meter show the battery doing when you switch off.

[Ardent]

Going back to the original post
I have light staying on intermittently. Battery combined with handbrake and no temperature reading.
This has happened on a couple of occasions. Today I popped into a shop, restarted the car and they've gone out - back to normal. Sounds very similar to an old thread where I believe a new alternator sorted it but mine is intermittent. Any thoughts?

Do alternators do, intermittent? I was under the impression, they only ever got worse. Just a one way street.
With ref to the handbrake and no temp reading. Would this not suggest a short somewhere. Chaffing as they pass through the body work. Vibration, temp, road surface , atmospheric conditions could very easily be the minor variations between shorting or not.
Not that I could, but could you use the multi-meter to trace the handbrake and temp cables and check for continuity?

A lot more time consuming, but as @shnazzle said, the figures you gave for the alternator and Batt read healthy.

[Dev]

Going back to the original post
I have light staying on intermittently. Battery combined with handbrake and no temperature reading.
This has happened on a couple of occasions. Today I popped into a shop, restarted the car and they've gone out - back to normal. Sounds very similar to an old thread where I believe a new alternator sorted it but mine is intermittent. Any thoughts?

Do alternators do, intermittent? I was under the impression, they only ever got worse. Just a one way street.
With ref to the handbrake and no temp reading. Would this not suggest a short somewhere. Chaffing as they pass through the body work. Vibration, temp, road surface , atmospheric conditions could very easily be the minor variations between shorting or not.
Not that I could, but could you use the multi-meter to trace the handbrake and temp cables and check for continuity?

A lot more time consuming, but as @shnazzle said, the figures you gave for the alternator and Batt read healthy.

Yes they can go intermittent for awhile. Best way to check is to test the diode pack in the regulator by seeing how much AC voltage is leaking though. When the alternator is on its way out it will not regulate well and could cause over voltage and then under voltage intermiteently, it  will also cause the charging light to light up or the dash lights to light up unusually because it is generating too much AC voltage ripples.
 
 This is why you have to measure AC voltage to know the health of the voltage regulator as that is the main part of the alternator that goes bad however there are other causes like a slipping serpentine belt which is rare but does happen.
  I wish more people would understand how to test for a failed alternator since the diagnosis is easy.  Just measuring voltage with a multimeter is not enough if its in the beginning stages of failing.
Sometimes you can have one failed diode in the pack and everything seems normal but over time it can ruin your battery or mess up your electronics.


 

[rusty0273]

So, had the battery checked at Halfords and reads as a 'Good Battery'.
I didn't do the AC check on the alternator as Dev suggests, so will try that next.
Was assuming a new battery would sort it but its never that simple!

[Alex Knight]

It's the alternator.

Just replace it.

[1979scotte]

It's the alternator.

Just replace it.

Agreed even the teenagers at Halfrauds can test a battery

[shnazzle]

It's not that fun a job I can tell you... But it's certainly not horrendous.