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Conference terri::cars_uk

Title:Cars in the UK
Notice:Please read new conference charter 1.70
Moderator:COMICS::SHELLEYELD
Created:Sun Mar 06 1994
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:2584
Total number of notes:63384

978.0. "MGB Alternator problem" by RDGE44::JONESK (Hackers do it over the phone) Thu Mar 08 1990 11:56

    Does anyone have any experience with MGB alternators ?
    I have the following problem:-
    
    As I drive along, the red ignition light glows.
    Thus the battery isn't being charged as well as it should be.
    
    On the motorway the lamp glows brighter but when I get into town
    and reduce my speed, the light fades slightly.
    
    I am driving along and the lamp is glowing. If I now put my headlamps
    on and the heater fan on, the lamp fades to almost nothing indicating
    that its charging almost 100% !
    
    I've obviously got a problem with my alternator, probably the brush
    box???????
    
    Any hints or previous experience ??
    What is it like to replace? Tricky job, long, special tools??
    
    Thanks,
    Kris..       
    
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978.1BRIANH::NAYLORPurring on all 12 cylindersThu Mar 08 1990 12:347
This appears to not be an alernator problem, but a control box problem.

I take it your battery hasn't gone flat yet?  In which case you're pumping
out lots of amps, but the box isn't regulating them properly and the red
light is indicating a fault condition.  If it really was the alternator not
charging, you would run out of erg juice pretty quick by loading up the
battery.
978.2ANNECY::MATTHEWSM+M Enterprises. Thats the CATCHThu Mar 08 1990 13:4812
    I thought the alternators and control boxes were mutually exclusive ...

    I have seen this type of thing with dynamos, but not with alternators.

    It does sound like something to worry about to me. Perhaps the alternator
    is putting out too much current ... perhaps worth checking the battery
    temperature. They have been known to boil !!!

    Apart from that, there is noting special about the MG alternator as far
    as I am aware ...

   Mark
978.3diodes..?KERNEL::HUTCHINGSumop episdnThu Mar 08 1990 14:204
    check the diode assembly to see if one has blown...
    This happened on an alternator of mine once, giving the same probs
    as you describe, a replacement assy costs about a third of the price
    of a new alternator. 
978.4Seen this beforeVANILA::LINCOLNThe sun has got his hat onThu Mar 08 1990 14:596
	This is (as stated in .-1) a partial failure of the rectifier.

	I reckon it's cheaper to get an exchange alternator than to
	attempt to fix it, but could be wrong.

	-John
978.5Right and a wrong wayVOGON::MORGANWhat part of NO don't you understand ?Thu Mar 08 1990 15:138
    And am I right in thinking that there is a rigt and a wrong way to fit
    a new alternator ??. The right way , it works !!, the wrong way is that
    you overload the alternator and blow it.
    
    Could someone a bit/more knowledgable please confirm/deny and explain
    
    Rich
    
978.7ta...!!!!!KERNEL::HUTCHINGSumop episdnThu Mar 08 1990 17:2713
    re: .4
    
    Thats it...!!
    
    I couldn't think of the assembly name....
    
    rectifier....set term/commit_to_memory
    
    ta..
    
    it did fix the prob tho'
    
    Paul
978.8Cheaper than a new alternatorRUTILE::SMITH_A2 down and 1 to goThu Mar 08 1990 19:405
    I'll endorse the rectifier solution.
    
    I found it a very easy fix to do. Whip out the Alternator, take
    off the end cover at opposite end to pulley, replace rectifier,
    reassemble. Robert's your fathers brother.
978.9I've been there as well.KERNEL::MARTINFri Mar 09 1990 10:2310
    
    I had the same problem with a Lucas alternator on a TR7 about 7
    or 8 years ago.
    I took it to a Lucas agent it took him about 2 mins to test.  His
    verdict was a blown rectifier.  I could have an exchange alternator
    there and then for 21 pounds or he could repair it for 7, but if
    he repaired it I would have to wait until that evening to collect
    it.
    I had it repaired and even got a years guarantee.  Had the car for
    another 2 years with no problems.
978.10SHAPES::ALFORDJIce a specialityTue Mar 13 1990 15:579
    
    sounds like the regulator...
    
    this is a common fault with VW Polos/Golfs after the head has blown.
    
    oil has dripped onto the altenator/regulator and the solution is to
    very inexpensively replace the regulator.
    
    the fault (in the VWs) is not detectable during the normal tests.
978.11Please refer to note 1266 UKCSSE::RDAVIESLive long and prosperTue Oct 30 1990 16:175
    Please put all future MGB releated material in note 1266. 
    
    This topic will be write locked
    
    Richard (co-moderator)