CURLY Posted July 30, 2009 Share Posted July 30, 2009 i dont think my alternator is charging correctly. i just put a meter on the battery with the engine running and it only read 13.4v instead of 14.5v. i assumed it was because the engine was on tick over, but even revving it right up it still wouldn't go any higher than 13.5v. is there any way of testing if its my battery at fault, or if its the alternator? and if it is the alternator, is there any way to fix it? cheers, CURLY Quote Link to comment Share on other sites More sharing options...
headhunter Posted July 30, 2009 Share Posted July 30, 2009 Check the output at the Alternator Should be 13.9-14.4v or thereabouts. If that is OK you may have a poor cable (live or earth) or connection or a duff battery. Quote Link to comment Share on other sites More sharing options...
reb78 Posted July 30, 2009 Share Posted July 30, 2009 Cant you check the alternator by measuring the voltage with the alternator under load? If the alternator isn;t working properly when you turn the heater main beams etc on, the voltage will drop dramatically as all the drain is put on the battery. If there is no dramatic drop, its not likely top be the alternator? Quote Link to comment Share on other sites More sharing options...
CURLY Posted July 30, 2009 Author Share Posted July 30, 2009 output at the alternator is 13.9v and at the battery now its 13.8v. think the battery was a tad flat, so hopefully now its been on charge for a while, it should be better. i thought they should be at 14.5v when the engine is running though.. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 30, 2009 Share Posted July 30, 2009 Some alternators put out 13.8, some put out 14.4. Quote Link to comment Share on other sites More sharing options...
CURLY Posted July 30, 2009 Author Share Posted July 30, 2009 i drove about 4 miles just now on a charged battery that started to die a bit after cranking, the battery meter went above the half way point, so about 13.5v i guess, parked up, went in a shop to buy some sweeties~! came out and it started ok, but a bit slow to crank, drove back and stopped, and tried to start it again but the battery was really slow to crank it over?? that was a brand new battery too. bit small for the purpose, but as a tester to see if the big battery i have is bummed or not.. i've put my old big battery back in it now after giving it a top up on the charger, so hopefully it will be ok. but if its not, and i do need to get a new alternator, does anyone know if i can get a bigger one for it? its a 1989 110 2.5td. shame they dont do a 14v battery, cos when i used the starter jump pack thing it turned over really fast and started after a few cranks! CURLY Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted July 30, 2009 Share Posted July 30, 2009 If the alternator regulator pack is dying it could be generating ~13.8v when running but draining the battery when switched off. As for bigger alternators, that's been done a hundred times - you can buy genuine ones for £££ or rummage round the scrappy for something that can be made to fit, Mondeo ones are cheap and stick out 90A but fitment will depend on your brackets. Quote Link to comment Share on other sites More sharing options...
Aragorn Posted July 30, 2009 Share Posted July 30, 2009 A good working alternator should output 14.1v Thats the optimal charging voltage for a 12v lead acid battery. 13.8v is the minimum that will properly charge a battery, and anything over 14.4v is dangerous and will start the battery gassing. I'd see what the voltage between the alternators case and the B+ terminal. If its managing 14v there, but not at the battery, its a cabling fault. Try giving it 2-3krpm and turn on as much electrical kit as possible and see what happens to the voltage. Quote Link to comment Share on other sites More sharing options...
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