Help - Fiat Tipo electrical problems!

Hi,
Been having problems with an 89 1.6 Fiat Tipo. Basically got a phone call of the Mrs. last week saying that it wouldn't start, RAC towed her back home
and said the alternator was faulty as battery had died. Charged the battery, fired it up on the driveway, 14.4 volts coming out of the alternator. Thought "oh well, one of those things". Left it overnight, next morning totally dead, 70mv coming out of the battery.
OK, must be a knackered battery, even though it's only 18 months old. Took it back to the store, they tested it said there is nothing wrong with it. Charged battery, start car, only 13 volts coming out of the alternator.
Next step - check all lights etc are off when ignition off, turn off courtesy/glovebox./boot lights. Same problem. Pull fuse for radio/immobiliser. Same problem.
Notice battery light on faintly and assume one of the diodes in the alternator has gone, think that may cause battery drain when not charging so replace the alternator and fanbelt - battery light now extinguished, but still only 13v coming out of the alternator.
So, on to today - took battery off the car and charged till full. Reports 12.91v off load, as soon as I connect the battery to the car it drops to 12.05v. Disconnect again and it rises to around 12.75v.
Any ideas? I'm running out of theories here! Checked all earths, they're ok, so signs of smoke or anything getting warm....
Hellraiser...........>
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There must be a significant electrical load draining your battery if the voltage drops as low as that when you connect it, assuming that the battery is indeed a good one. Have you tried pulling out all the relays yet?
--
Stuart Sharp

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That's the next port of call - ruled out the battery by hooking the one out of my car up, that drops from 12.8 to 12.2v, connecting it to my car it drops from 12.8 to 12.77, so there must be a load of sorts. I would expect some sort of smoke or at least the battery to get warm as it must be drawing a fair bit of welly for that to happen!
Hellraiser...........>
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Sure is. I can't recommend measuring it, unless you have a DC clip on ammeter. An in line one like you get on a multimeter is usually 10A max and I reckon the load you have would blow that. It's just a case of disconnecting things until you get rid of the volt drop (or the spark) when you connect the battery.
Good Luck!
--
Stuart Sharp

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There's an electric manifold heater (called a PTC in the book). It draws a fair current but only when the ignition's on and the engine's cold....
Maybe that's somehow stuck on and draining the battery? You can disconnect it without causing any running problems, there should be a cable coming out from under the inlet manifold. One of the 20A (I think) fuses is devoted to it.
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Pulled the fuse for that, made no odds. I *did* fine the cause of the problem though (or at least found a clue) - there is a secondary fuse board to the right of the main one, there was a 20A fuse *melted* in there, but not blown. Pulled it, and no voltage drop, also the car seems to still work despite the fuse being pulled. Anyone know what the fuses in this board are for?
Hellraiser..........>
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Haynes book says the fuses here are: inlet manifold heater, electric windows, headlamp wash/wipe.
And the PTC fuse is a 20A one. So, which was the other fuse you pulled that made no odds?
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Good question, it definitely sounds like the PTC fuse I've pulled as that would draw sufficient load to flatten a battery within a couple of hours wouldn't it? Next question is to find out why it is staying on when the ignition is off - stuck relay perhaps?
Hellraiser............>
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once came across a stuck hrw relay on an omega that killed the battery pretty quick
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Yep, sounds like that is the likely candidate having had a look at the wiring diagram. Will pick one up next time I'm near a scrapyard, although it runs fine at the mo without the PTC - guess that will change when the winter comes :(
Cheers all
Hellraiser.............>
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