Alternator required

[royzels]

Hello again... My alternator on tick over is showing approx 12 volts at the Battery... On reving the engine the reading does not go up very much....... I presume that my Alternator is on its way out, unless im informed different by you guys................As usual any advice would help me and if it is the alterntor, anyone got one for sale......................Cheers again Roy.

[steve2006]

Is the Battery going flat or the charge warning light coming on?

[ambermarine]

It should read between 13.8 volts and 14.2 volts at 2000 rpm if it is charging the Battery, before you start changing the alternator put another Battery on the car and recheck the voltage because the Battery could be on its way out and taking a limited charge .

The way to check the alternator is  using a multimeter place the positive red probe on the alternator positive terminal and the black negative probe to a earth on the car not the alternator case.

That way you take out the Battery influence and get a true alternator output reading.

[Britprius]

You need to check the current into the Battery (amps) after discharging the Battery by leaving the headlamps on for 5 minutes without the engine running. An output of at leased 30 amps is expected. A clamp type meter is useful for this. Although I agree 12 volts on charge is low how accurate is your volt meter? Check with another meter to see if you get the same result.

Other things to check is how tight is the drive belt, and with a volt meter check the voltage from the negative Battery terminal to a clean bolt or piece of metal on the engine with the engine revving gently and headlamps on. This reading ideally should be zero but will possibly be 0.1 to 0.2 volts. Check this reading again while turning the engine on the starter. The reading will be higher but should not be over 0.5 volts. High readings show a bad connection between the Battery, the car body, and the engine.

Do not condemn the alternator until these checks have been done.

If you do not have an amp meter try putting a good quality jump lead from the Battery negative terminal to the engine on a clean bolt, and take the voltage readings again.

John.

[royzels]

Hi all ...The Battery does not go flat as I have one of those chargers that you can leave on charge all the time...... I will try what you suggest.. Thank you.

[royzels]

Hello.... I have checked with another volt meter, but the readings are approx the same, not much above 12 volts... Hope this helps................. Thank you.

[JohnDavis]

I have just taken my spare alternator into a local specialist to be rebuilt, these independent specialists are very good, (or at least mine is) and they normally charge 65 to 100 pounds.

[MLW]

I always have found a good independent auto-electrician to be way better than any main dealer technician. They diagnose, (they know about electricity!) and then fix, rather than replace everything. A good one might charge £20 to tell you what is wrong. Money well spent I think. They do get it right!

[royzels]

Thanks to you all...Information gratefully received.............Roy.

[Britprius]

On 9/27/2017 at 7:41 PM, royzels said:

Hello.... I have checked with another volt meter, but the readings are approx the same, not much above 12 volts... Hope this helps................. Thank you.

Roy the problem with checking the voltage at the Battery is that if there is a bad connection between the Battery, and the alternator "most commonly in the negative wiring" the alternator will output the correct voltage, but it does not reach the Battery. It is good that you have eliminated the possibility of a faulty reading meter. 

 A couple of volts "voltage drop" can easily be lost in the resistance of the bad connections. Putting a jumper cable from the negative cable to a clean bolt or piece of metal on the engine and then taking the voltage readings again with the engine running will remove the problem if there is one.

This may well not be the problem, but it costs nothing to check as does checking the belt tension, and condition.

John.

[royzels]

Hi all.. New Alternator fitted and problem solved...cost of Alternator £133... Fitting £84..... Job done.

Also new steering pump fitted......Cost ...Pump.Approx  £150   Fitting £190.....Had my bumps felt I think........... Anyway again job done

Thanks to you all for your help as usual...a big special thank you to you all............ Roy.

 

[dendonc]

On 9/27/2017 at 4:31 PM, royzels said: