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...........>
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

So it looks like there is a load on the battery, and the simplest approach may be to wire a 12V bulb, say 8W, between one battery connector and the battery post. If it comes on then you pull fuses and disconnect things until it goes off. The one that turns it off is where the current is going. Radio and immobiliser shouldn't draw more than a few milli-amps, not enough to light the bulb, otherwise after two weeks at the airport the battery would be flat. Put long thin figure 8 flex lead on the bulb and you can have it in the car, where you can see it, while you pull the fuses. Insulating tape the exposed bulb connectors so you don't short the battery onto metalwork.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.