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Alternator replacement

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Alternator replacement

Postby mitchellsdad » Tue May 07, 2013 7:50 pm

How big a job is it to replace an alternator?
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Re: Alternator replacement

Postby Bonovox » Tue May 07, 2013 10:07 pm

Are you 100% that the alternators knackered? A quirk of the WR1 is that it needs to have sided lights on for the alternator to charge the battery.

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Re: Alternator replacement

Postby chiroman » Wed May 08, 2013 4:59 pm

Replacing alternator is a straightforward. Had mine tested and rebuilt at local company. A new one would be more expensive but quicker and longer warranty I guess.

They are apparently "smart" alternators which regulate their output depending on the electrical load etc. as seen by the ECU.

If your battery is going flat it could be discharging via shortcircuit diodes in the alternator which would also reduce it's output.

Mine had no fault lights displayed but output volts were low when tested and battery would go flat even when driving. The car would start popping and banging and hardly run, very alarming, all down to low volts for cars systems.
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Re: Alternator replacement

Postby mitchellsdad » Fri May 10, 2013 5:34 pm

It is very interesting to note that the side lights need to be on for alternate to charge a battery. Is that really true?
My issue is that the car is not run that regularly. I worked on the car Sunday, then took it for a blast round the block for 10 mins. Tried to start car on Monday morning and nothing! Put car on charge for whole day and night and she started no problem. Took it for a longer spin.....45mins. Put in back on charge trickle charge and readings were low! I guess I need to get an electrical expert to take a look but would be interested if anyone else has similar problems
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Re: Alternator replacement

Postby chiroman » Sat May 11, 2013 3:23 pm

I had similar problems and had read all the blurb about running on sidelights which I didn't believe. I had the battery tested at Halfords and it was ok so I charged it for about a day and a half but problem persisted.

With the engine running I checked the alternator output with an accurate digital voltmeter and also switched on all electrical loads individually and together to see if volts increased. There was a small increase but the volts were still low. I tested the wife's 07 1.4 Corsa and the volts were higher than the scoob.

One of my tests was to hook up the test meter in series with the battery as an ammeter obviously with the engine not running or being started. This measures the drain from the battery and should be only a few milliamps. If the alternator rectifier diode pack is faulty the current fron the battery can drain down via the faulty diode and so discharge battery, also the output volts will be low! Incidentally the alternator is a three phase ac generator whose output is converted to a dc voltage by the rectifier diode pack. The output voltage level from the alternator is regulated by feeding a dc excitation voltage into it and with input from the ECU regarding electrical loads.

Local auto elec repairers tested alternator and it was faulty, probably the diode pack, all was ok with rebuilt one but this lead to another issue, see below. I also now have a new Bosch battery but it will still go flat occasionally as the car is sometimes not started for a few weeks.

It always goes flat at about 10.30 at night, I hear a car alarm going off and realize it's the scoob again and the battery's low. Lot's of rushing around to hook up the battercharger then the alarm stops and I leave it to charge up.

So the charging system was fine but now I could hear a sort of whining sound from the front of the engine! What the hell! After much listening I thought it was the air con tensioner idler wheel, so replaced it and also the accessory belts - sorted. Like fcuk. Finally discovered the alternator was noisy which was a surprise as new bearings had been fitted! The guy at the auto elec shop once again replaced the bearings with a different make, well that was his story, and silence.

I don't drive around with the sidelights on but the heater fan is always on!
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Re: Alternator replacement

Postby mitchellsdad » Sat May 11, 2013 3:44 pm

Ensured that battery charger I bought had a trickle charge function. Bit of a pain wiring it up after trips but ensures charged battery at least..... alarm going off at night would drive me up the wall! Things seem ok at present, so touch wood cause was a flat battery due to low usage. Also, with Scooby's having high compression ratios, anything but a fully topped up battery I guess is asking for trouble :wink:
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Re: Alternator replacement

Postby Hall12 » Fri Mar 28, 2014 11:55 am

I've changed my own alternator before, and it is a straight forward job, but I'd sure want to have the battery and alternator tested before I started ripping it out.

I went with a rebuilt alternator for my car. It was about 30% less than new and had the same warranty.
Is National the best bet?
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Re: Alternator replacement

Postby silver-sonic » Fri Mar 28, 2014 7:47 pm

mitchellsdad wrote:How big a job is it to replace an alternator?

easy job.
if local i could help .
im in west yorks
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