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Alternator failed?
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Alternator failed? 2 years 11 months ago #195662

I've been using the TF a lot recently without any problems until today.  Last week on the way home the battery charging light came on.  Pulled over to check the alternator belt was OK, left the engine running, and when I got back into the car the light had gone out.

Used the car over the weekend for a short journey,  no issues.

Went to use the car today, all appeared OK, but got a mile down the road and the car started shutting down, warning lights coming on and the power steering stopped working, but not the battery charging light. Coaxed the car home.  So I'm assuming the alternator has packed up  but if so why was the battery warning light not come on again, after the initial time last week?

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Alternator failed? 2 years 11 months ago #195674

Does the alternator light come on when you switch the ignition on before you start the car?

Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.

MG - the friendly marque.

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Alternator failed? 2 years 11 months ago #195679

No it doesn't, so I took it out last night and it has continuity through it so appears to be OK. I've now charged the battery and with the engine running get 11.55v across the battery, no change when I rev it. I've got the alternator out to check for any obvious faults of which there are none, so last stage is to put it back in , check all earths and give it another go, if still no charging then I assume dead alternator?

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Alternator failed? 2 years 11 months ago #195680

One quick and easy thing to check is the alternator fuse.  
.  Is the diode pack replaceable on the TF alternator?  I don't know.

Also, a fully charged battery should supply about 12.5V, not that this sounds like your problem.

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Alternator failed? 2 years 11 months ago #195681

Is the diode pack replaceable on the TF alternator?  I don't know.


It's called an alternator regulator.  Available online and from ebay, e.g.
MGTF MG TF Alternator Regulator for YLE102430 Brand New mgmanialtd.com
Buy It Now


Oh.  Just noticed that the eBay widget doesn't work anymore.  Try here:
 
MGTF MG TF Alternator Regulator for YLE102430 Brand New mgmanialtd.com
Buy It Now

 
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Last edit: Post by BruceTF135.

Alternator failed? 2 years 11 months ago #195682

Battery charged, alternator taken off and inspected, no obvious damage etc. Alternator back on, connector sprayed with switch cleaner, all back together, additional earth run from battery to Alternator body using a set of jump leads, car started, 11.5v at battery, 11.5v between alternator feed terminal and body of alternator, so can only assume alternator duff.

Two questions:

Why isn't the battery warning light illuminating- is this fed from the alternator diode or something?

Alternator regulator fix sounds interesting - is there any way of checking if this is the issue? Would this explain the charging light not working?

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Alternator failed? 2 years 11 months ago #195683

No alternator light? that's your problem............when you switch the ignition on the alternator light should turn on until the engine starts, the purpose of this is to excite the alternator into charging.......no alternator light - no charging
Check the light bulb in the alternator light and the wiring connections to the alternator.
BTW you can't substitute an incandesent bulb with a LED bulb, the LED bulb won't draw enough current to start the alternator.
"Keep calm, relax, focus on the problem & PULL THE BLOODY TRIGGER"

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Alternator failed? 2 years 11 months ago #195684

I don't know, to be honest! Just trying to be helpful. There are many people here far more knowledgeable than me. Perhaps they will know.

Did you investigate the fuse?

Has the bulb blown on the dashboard? I cannot imagine why else it wouldn't light when you turn the ignition on. Fuse 25 under the dashboard?

Have you looked at the circuit diagram? You'll find it under Community/Downloads.

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Alternator failed? 2 years 11 months ago #195686

Had exactly the same happen on my TF (no ignition light and no charging), and it was the alternator.

First test, disconnect small wire from alternator and ground it. The ignition light should come on (ignition needs to be on for tests).

If it does not, then the bulb has failed, or the wiring has failed.

If the Ignition light illuminates when the wire is grounded, then a field wire in the alternator has failed. This is a winding that generats a small magnetic field that is needed for the alternator to start working. New alternator is only solution.

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Alternator failed? 2 years 11 months ago #195687

Thanks, latest is both fuses ok, 12v at the ignition lamp feed from ign., voltage other side of lamp and diode on back of dashboard so that end ok. I need to check at alternator plug but its chucking down with rain so that'll have to wait until tomorrow.

So sounds like I've got the same problem as G0RSQ, I've ordered a new regulator for the alternator, could that be the issue?

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Alternator failed? 2 years 11 months ago #195716

Regulator fitted, all working perfectly, battery charging.

So, what I've learnt, if your alternator isn't charging and your ignition light isn't coming on, these are the steps:

1.  check the 40A fuse on the rear engine bay bulkhead 
2. Check fuse 25
3. Disconnect plug from alternator and with ignition 'on' ground the brown and yellow wire in the plug, if the battery charging light comes on when you do this the fault is with the alternator 

The most likely fault on the alternator is a failed regulator ( if it was anything more serious than this i can't imagine parts suppliers wanting to recondition them)  and these can be bought for around £35 and are easy to fit.
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Last edit: Post by talkingcars. Reason: Clarity

Alternator failed? 2 years 11 months ago #195719

I had similar problems and i found that the battery light circuit is also a trigger for the alternator, my light didnt come on and the light didnt come on, i managed to get my hand to the dash battery lamp and gave it a little twist and it located better, switched the ignition on, light iilluminated started engine light went out and the alternator give an output, no probs since

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Alternator failed?
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