Allegro Club International

[alan wilson]

Hi all
After a long miserable period of suffering suddenly flat batteries, I`ve finally found out what`s really going on. The battery would be fine for an inderterminate time, then next time I parked the car up it would go flat pretty quickly. I was going to drive to the Swan in Knutsford on Friday for the monthly meet and fitted a brand new battery as the car had been stood for a month whilst I was in hospital and was subsequently flat. I started the car and thought I`d let it warm up and charge the new battery for a while. Luckily, as some of you will know, my Aggro is customised with a VP dash to which I fitted LED warning lamps instead of bulbs but still has the voltmeter - and I noticed the volmeter went rapidly into the red zone, above 15 volts! At this point I decided a 60 mile trip might be a bad idea. After a minute or so, the charging LED suddenly came on for a second, went out again and the the voltmeter went back to around 14 volts which is normal. This happened to me years ago with a Ford Cortina whilst I was driving a long distance, the result was a duff battery with acid steam coming out of all 6 cells. The problem with this fault is that the ignition lamp stays off. I was showing my son what was happening today and exactly the same thing occured. I got out of the car and lo and behold, acid running out from under the front of the car directly under the battery tray! I have a nice clean area now on the paving stone, and quickly hit the battery, inner wing and driveway with the hosepipe to dissolve the acid which was coming out of the breather of the battery. I know that the reguator unit in the alternator is to blame, my only worry is that it may be my fault due to the mod I made to the charging system to make an LED work instead of a bulb for the charging lamp. I fitted a charging relay which feeds the field windings direct where normally it would be fed via the charging lamp bulb, but that won`t work by simply replacing the bulb with an LED as the current flowing is insufficient to excite the alternator - the question is, has this fried the regulator unit...thoughts please before I get the alternator fixed tomorrow ???
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Well someone had to do it.....

[M. Irvine]

Alan,
It is difficult to understand which way you have integrated the charging relay and the LED into the system. If you could give me more details with perhaps a wiring diagram, I hope I will be able to help you.
Although a short service life is suspicious, I am bound to say however that the quality of some replacement alternators and other electrical goods leave a lot to be desired, and even a 'good' make on the box does not always meant that it was supplied by that manufacturer or remanufacturer. (Something I have been involved with, on behalf of others)
Merv. (Membership Secretary)
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ALLEGRO = Agile, Lively, Legendary, Economical, Genial, Reliable & Outstanding.

[alan wilson]

Hi Merv
Thanks for your interest - to clarify, I re-routed the warning lamp wire to the energising coill of a 12V 30A relay. By applying 12V from the ignition switch on the opposite side of the relay coil, this causes the relay to switch on with the ignition and effectively replace the 12V feed from the original warning lamp bulb, exciting the field windings and allowing the alternator to charge. When the alternator output rises above 12V the resulting null voltage allows the relay to open and switch off the LED which is switched by the normally closed relay contacts. I`ve calculated the load from the energising coil, and it`s 1.8W/150mA ie roughly equivalent to the load imposed by the ignition lamp. So I can`t see that this can have damaged the regulator, after all it doesn`t care if the load is coming from a 2W bulb or a 1.8W coil in a relay. I`m just a bit wary that the fault could re-occur whilst driving causing a breakdown. Hving said all this, the alternator is the original, it`s only covered 32k but it is 29 years old! Let me know what you think. The new alternator only cost £27 inc VAT so we`re not talking megabucks, just the thought of breaking down on the way to Tatton Park in two weeks is not nice
Cheers
Alan
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Well someone had to do it.....