tiddy1 Posted December 6, 2011 Share Posted December 6, 2011 How can I tell If my alternator is charging the battery properly, or more to the point why it is not. The car is left on trickle charge so its fully topped up on a brand new battery I drive to work and back ( 6 miles each way int he dark, and rain ) park on the drive and there is not enough juice in the battery to start the car to get it in teh garage. the car is a 2 litre duratec running a nippon denso alternator. when you run at fast idle I can measure 14+ volts across the battery which would imply that its charging so I can only assume that I am using more current than is going into the battery but where? The only thing I have noticed is that the dash ignition light never comes on ever can this be related, I just thought this was a +ve feed switched to earth through the alternator I assume if I took off the +ve battery lead and ran it through an ammeter I could see the current draw when running? and suggestions as the best way to fault find as its getting rather annoying Simon Edited by - tiddy1 on 16 Dec 2011 14:33:59 Link to comment Share on other sites More sharing options...
Mr Locust Posted December 6, 2011 Share Posted December 6, 2011 The dash light needs to come on. Then go out. The bulb is fed by +12V from the ign switched circuit. Once charging, the bulb terminal of the alternator is raised to +12v so the bulb extinguishes. Link to comment Share on other sites More sharing options...
Paul Deslandes Posted December 6, 2011 Share Posted December 6, 2011 If you have 14Volts across the battery with the engine running then it must be charging and should already be in a good charged state. If it fails to start the car after a short break, either the battery is not holding a charge and is faulty, you have a high resistance path between the battery and the starter, or something is draining the battery after you switch off the engine. Before you try to restart the car, check the battery voltage and see if its at somewhat greater then 12V. Then switch on and crank to see if the battery voltage falls under load. If it fails to crank properly but the battery voltage stays up you have a connection problem. If the voltage drops I would suspect the battery. One thought, I have read on BC recently that the Redline alternator bracket is insulated and you have to have a heavy current rated cable between the body of the Denso alternator and the block or chassis. If you have this arrangement, it might be worth checking whether this is your problem. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted December 7, 2011 Member Share Posted December 7, 2011 New battery and 14V when running... High resistance path as Paul suggested. The voltage is OK but can the connections handle enough current for the starter to turn the engine? Bad battery connections or earth strap? What exactly happens when you try and start... with a voltmeter in place (or the lights on)? Jonathan Link to comment Share on other sites More sharing options...
tiddy1 Posted December 7, 2011 Author Share Posted December 7, 2011 When I try and restart everything goes dim and the solenoid does not even click in, some times I dont even make it home and I presume the battery voltage drops so low tthat the ECU cant cope, it splutters and misfires for a bit then dies. As I said I seem to be getting a4+ volts from the Alternator but its as though I am drawing too much current so the battery is going down quicker than it can charge. I only have the lights on and may be the wind screen wipers so I need to check if they are drawing huge currents Simon Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted December 7, 2011 Member Share Posted December 7, 2011 I'd clean and inspect all the contacts from the battery to the starter. Jonathan Link to comment Share on other sites More sharing options...
Sheds Moderator Posted December 7, 2011 Share Posted December 7, 2011 As JK says, plus get a voltmeter and measure the voltage *directly across the battery terminals* when the engine is cranking. Disable the ignition first so you can get a good old crank for 10-20 sec or so without the engine starting. Any battery should hold 9V or better. If it doesn't, it's dead, new or not. This is what it sounds like to me. If it holds the voltage up (and a new battery in working order should sit there holding 10V at least, churning away on the starter saying "yeah, anything else you want?" for a good few tens of seconds without wilting) then you have a resistive contact somewhere - a bad connection to the starter, a bad earth strap, or similar. Diagnosis here is to use a jump lead to ensure a good earth between battery and engine block and see if this makes a difference. If any of this isn't clear post up again and we can go through it blow by blow till you get the diagnosis you need. Link to comment Share on other sites More sharing options...
Jason Plato Posted December 7, 2011 Share Posted December 7, 2011 if its not a dead battery then it could be that the alternator is not spinning fast enough and often enough to charge - this can be due to the size of the alternator pulley or that the alternator is too small in amps for all the electrics to run at low speed ?. sounds like dead battery to me Simon. dj Link to comment Share on other sites More sharing options...
tiddy1 Posted December 7, 2011 Author Share Posted December 7, 2011 I changed the battery because the old one was showing the same symptoms, may ne the old battery was fine. I have had this alternator set up for the past 3 years and haven't had many problems, but I may look at speeding up the alternator. for the past 3 years the ignition light has never worked. I will do a full run through of earths etc to see if I can improve things. When the battery is fully charged the engine will crank like a good'un and start instantly, but I will look at the voltage during that cranking When I broke down last time I connected up a jump box and drove home with that left attached, however I did not get all the way home as everything was flat and I had to push the last 100 yards home! Simon Link to comment Share on other sites More sharing options...
Paul Deslandes Posted December 7, 2011 Share Posted December 7, 2011 You wouldn't be the first 7 owner to buy a new Banner battery and find its as knackered as the one its replacing, although its worrying that the support pack ran flat as well. It could be worth taking the car to an Indy auto electrician and have him test it all out as you might have an alternator problem, although I can't quite see what from the data at the moment. Not sure about the Denso alternator but the lamp can form an essential part of the charging control circuit so I think I'd investigate why its not working before I splashed out on another battery. If your battery is showing 14 Volts at fast idle then you don't need a higher ratio pulley arrangement which will only stress (over rev) the alternator at higher engine speeds. Link to comment Share on other sites More sharing options...
tiddy1 Posted December 7, 2011 Author Share Posted December 7, 2011 Its not a banner battery, but a sealed lead acid/ gel type, I gave up on banners long ago. Think I need to take all the elecee bits off and put it all back with new earths and shiney contacts Simon Link to comment Share on other sites More sharing options...
Paul Deslandes Posted December 7, 2011 Share Posted December 7, 2011 If your battery is a PowerVamp type and has been allowed to heavily discharge and not been fully recharged, it might not be holding a charge. If so it needs to be fully charged with a proper battery charger, rather than a maintenance device that doesn't deliver enough current. Even though the voltage comes up, it may not be fully charged. It still doesn't explain why the starter pack went down though. Link to comment Share on other sites More sharing options...
Sheds Moderator Posted December 7, 2011 Share Posted December 7, 2011 Before doing all this I would check out the existing battery. Also check for an earth leak - remove the -ve terminal and with everything switched off check for a current leak to earth with an ammeter. Link to comment Share on other sites More sharing options...
charlie_pank Posted December 7, 2011 Share Posted December 7, 2011 If you ran that setup for the last 3 years and just needed to replace the battery, I'd say that all is NOT well. I bought Kermit from Steve in 2002 and only got a new battery in 2008, that was after 18 months of no use AT ALL. I suspect that although your alternator is spinning, it is not charging the battery for some reason (possibly a dead battery?). When you measure the voltage across the battery, you're also measuring it across the alternator at the same time. Perhaps there's something up with your terminals? I suspect it will turn out to be significant that your battery discharging light does not come on with the ignition before you start the engine. Link to comment Share on other sites More sharing options...
anthonym Posted December 7, 2011 Share Posted December 7, 2011 When I broke down last time I connected up a jump box and drove home with that left attached, however I did not get all the way home as everything was flat and I had to push the last 100 yards home! that means no amps are coming from the alternator - it maybe there are only 7 volts across the battery at that point (istr that's when the (my) ecu surrenders), so it remains good for charging your mobile phone... which at the roadside is useful, in fact. If it wasn't sealed I'd say test the cells with a hygrometer.. other than that it needs to be tested electronically (instead of chemically), any tyre/battery/garage place will do that in a second. The alternator, may do different things at different revs; and it may have damage wiring or wiring that only behaves damaged when it gets hot. All I can think of here is remove it and have it tested, or indeed drive in to an auto elect who can test it in under a minute. Sympathise, these problems can be so slippery - fun to chase as long as it's not urgent. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted December 8, 2011 Member Share Posted December 8, 2011 Plus check the ignition lamp bulb asap. Jonathan Link to comment Share on other sites More sharing options...
fred_gustafsson Posted December 8, 2011 Share Posted December 8, 2011 Simon, I have the same problem with my duratec. It took me ages to figure it out but it basically boils down to the alternator pulley size. It's a bit too big so the alternator doesn't start charging the battery until you hit approx 1800 RM which means that if you are driving in slow traffic, you will run out of juice if your lights etc are on. Cambridge motorsports sells a 55mm pulley that fixes it. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted December 8, 2011 Member Share Posted December 8, 2011 Fred: Was your ignition light on all that time, before you changed the alternator speed? Jonathan Edited by - Jonathan Kay on 8 Dec 2011 13:02:53 Link to comment Share on other sites More sharing options...
fred_gustafsson Posted December 8, 2011 Share Posted December 8, 2011 Jonathan, Yes, whenever I was driving home in the dark and got a bit stuck in traffic I got this problem. I have now installed both a voltmeter and an ammeter so I know exactly what's going on. Idling with your headlights on and the radiator fan on means that you are using some 15 amps more than you are charging. It will run down the battery pretty quickly. The super simple solution is to remember to rev the engine for a few minutes before switching it off. The battery gets charged very quickly and 2500 Rpm. Fred Link to comment Share on other sites More sharing options...
tiddy1 Posted December 8, 2011 Author Share Posted December 8, 2011 Fred, following up on your suggestion I have been playing in the garage and you are right, at idle I get less than 12 v from the alternator, at 2000 rpm I get 14 v, looks like I need a smaller pulley, problem is I'm running a 5 groove belt so can only find a 44mm pulley do you reckon this would be too fast, its only a standard spec engine so rarely goes above 7K on the ignition side the lamp works its just the switching circuit through the alternator that needs investigating simon Link to comment Share on other sites More sharing options...
fred_gustafsson Posted December 8, 2011 Share Posted December 8, 2011 Simon. The CC standard 2.0 Duratec is a 66mm pulley. Changing it for a 55mm will give the alternator a max RPM of 17.750 at engine 8000RPM. This is OK as the stated max rev for the alternator is 18000. If Im doing the maths right, a 44mm pulley would take it about to 22100 which would cook it. Link to comment Share on other sites More sharing options...
tiddy1 Posted December 8, 2011 Author Share Posted December 8, 2011 Fred my crank pulley is 135mm so the 66 mm alternator pulley gives me 16363rpm @ 8000 (135/66*8000) the 55mm pulley will give 19636 rpm at 8000 the 44 mm pulley will give 24545 @8000, so as you say may be a bit over the top but I will therefore have to drop to a 4 groove pulley also cambridge charge nearly £50 for the pulley including postage, thats more than i paid for the alternator!!! may be just have to machine one myself Simon Link to comment Share on other sites More sharing options...
mic Posted December 8, 2011 Share Posted December 8, 2011 Cosworth do a 64 mm pulley for around £15, part number YDO 310 Link to comment Share on other sites More sharing options...
fred_gustafsson Posted December 8, 2011 Share Posted December 8, 2011 Simon, Cambridge charged me 27 quid for the 55mm pulley. A bit expensive yes, but they did swap it for free and paid for the return postage as I didn't have an air gun to undo the bolt. Link to comment Share on other sites More sharing options...
tiddy1 Posted December 12, 2011 Author Share Posted December 12, 2011 ok so I managed to find a pully for £6.70 so that will be along shortly, but I have been trying to figure out the charging light circuit. I have +12 V switched going in to one of the pins of the alternator plug, and the other pin on the alternator goes out to the dash light. Now when the ignition is on and the car not running I get +12 V at the bulb on the dash, but if you earth the other side of the buld it will not light? once the engine is running and I am getting 14+ volts across the battery (so I assume this means that it is charging) the voltage to the dash bulb drops to zero (but not earthed) The other side of the dash bulb is connected to +ve 12 V so I would have thought that the line from the alternator should be low when NOT charging and 12V when charging This is really confusing me if I have +12v on one side of a bulb and earth the other side I would expect it to light up, or is it because the current drops ? any thoughts would be greatly appreciated Simon Link to comment Share on other sites More sharing options...
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