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MG Midget and Sprite Technical - Cooked Battery

Help!

Little Blue began to smell like eggs, and after checking that none of my humorous pals had put a kipper on the manifold, I found a hot battery, fluid in the battery tray, and all the electrodes (or whatever they're called) uncovered and looking sludgy.

Everything still works, but summat's obviously up.

The set-up is neg. earth and alternator.
Nick

Alternator overcharging

clean up the acid mixture from the battery tray, top up the battery with water (I know "they" always say "distilled water" but frankly I think you will be buying another battery soon anyway) to just above te cell dividers (3/8" ish) and start the engine with a multimeter across the battery terminals, set on DCV the alternator should be sending no more than 14.5v max, better if it is at 13.8v.

Any more than 14.5v shows overcharge and will require another alternator or your present one given a new regulator.

If it has cooked though you may find it isnt charging at all, by now. Should be at least 13v running and that is weak.
Bill

Thank you very much, Bill. I shall be out there in the morning with my multimeter, and I'll let you know what it reads.

Lucky I have a 3 year Halfrauds guarantee - though I'll probably find it ain't quite as easy as that.
Nick

definatly sign of a bad regulator....good luck

prop
Prop

I don't think you'll have any trouble with the battery at Halfords Nick. I took one back and they just swapped it without even asking too much about what was wrong with it.
Bob T

Thanks chaps.

I've done the test, and the voltage across the terminals was 18.5.

The alternator's now swapped out, and the new one's showing 14.2.

Just one other thing, though. When I turned on the ignition, the engine made a quarter turn. I've noticed a bit of a jolt before, but I thought it was my new fuel pump, and I don't think it's been as big a jolt as today when I first switched on after doing the work. Also, the lead jumped off the coil!

What's all that about?
Nick

points partly open
tracking inside dizzy cap
spark runs to a cylinder with a fuel rich atmosphere and partial compression

ignition strikes a spark when turned on
spark hits wrong cylinder and causes a partial power stroke

how's that sound for a theory

check the cap for signs of tracking (Thin black sooty line running between posts)

If no new cap a tracking mark can be taken away for a while with a scraper (yup scrape it away with a pointy nosed tool, scriber or such) then renew the surface with Tippex or clear or non metallic nail varnish, along the scratch mark.

Buy new cap at first opportunity
Bill

ps, sorry you needed another alternator but expect to need a new battery soon unless you can ensure the old one gets a top up of premixed elctrolyte of the right strength. Not an easy fix for that, sorry Nick.

14.2v is fine
Bill

This thread was discussed between 26/04/2008 and 27/04/2008

MG Midget and Sprite Technical index

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