joste Posted June 15, 2014 Report Share Posted June 15, 2014 hi again,could some one please tell me what my amp dial should be reading under normal running? [ mine is near to the positive] many thanks steve. Quote Link to post Share on other sites
peejay4A Posted June 15, 2014 Report Share Posted June 15, 2014 Slightly in the positive is good. It should go higher just after starting as the battery is replenished. If it goes into the negative, say with the headlights on, heater fan on, radiator fan running then the battery is discharging and your alternator might be not up to the job. Quote Link to post Share on other sites
snowric Posted June 15, 2014 Report Share Posted June 15, 2014 it should read zero ie straight down when working correctly. If yours is reading 'positive' it is either charging the battery or a load has been put on that side of the battery and you alternator is powering that device, causing a current to flow across the ammeter so it looks like the battery is charging. This can happen when, for example, an electric fan is run from the battery post and switches on. Has it always done this or has it started after a new accessory has been added. R Quote Link to post Share on other sites
Denis Posted June 15, 2014 Report Share Posted June 15, 2014 Straight down like der man says! Quote Link to post Share on other sites
joste Posted June 15, 2014 Author Report Share Posted June 15, 2014 hi, thanks for the replies,its never done this before ,been having trouble with the carbs flooding,got car back Friday took it for arun today and noticed meter gauge hardly moved from the positive.. Quote Link to post Share on other sites
peejay4A Posted June 15, 2014 Report Share Posted June 15, 2014 So guys, when should it be in the plus? Quote Link to post Share on other sites
Guest ntc Posted June 15, 2014 Report Share Posted June 15, 2014 (edited) When under load, and charge required. Edited June 15, 2014 by ntc Quote Link to post Share on other sites
AlanT Posted June 15, 2014 Report Share Posted June 15, 2014 I think he means its gone hard over and is pointing at the plus sign. This is a disconnected wire somewhere I would think. Quote Link to post Share on other sites
peejay4A Posted June 15, 2014 Report Share Posted June 15, 2014 (edited) Assuming it's wired correctly, when there is a net current flow into the battery, ie charging, it should show a positive deflection. The cell voltage of a fully charged lead acid battery is about 2.1V, so let's be generous and say 13V total. The alternator should push the battery terminal voltage to around 14V, so with no other draw, other than ignition, it's very likely that there will be a positive current flow into the battery. Thus the needle will show a slightly positive deflection during normal running. Mine always have. Fair point Al. What does "near the positive" mean. I assumed a slight positive reading. If it's end stopped something's wrong. Edited June 15, 2014 by peejay4A Quote Link to post Share on other sites
RobinTR6 Posted June 16, 2014 Report Share Posted June 16, 2014 Sorry to jump in here but can anyone tell me how the ampmeter should be wired (looking from the front). Mine hits the end stop after starting, the sits about 1/4 from then on. Alternator is 45 amp replacement and Lucas pump wired via relay from starter post. Quote Link to post Share on other sites
snowric Posted June 16, 2014 Report Share Posted June 16, 2014 Robin I will have a look tonight but from memory alternator feed (brown and white) comes in on left side and battery is on right side. Using water analogy when alternator is chagrin battery current flows across ammeter and deflects right towards the battery side. For the guy with the 45amp alternator I found that running th original with my 55amp resulted in a massive swing to the right as, following my usual good old crank to get started, the battery drew c 40amps. I didn't like this - having blown on ammeter and so I fitted a smith 60amp ammeter and have disguised it as a Lucas's using and old 30amp lucas innards - still wip as it is too bright when lights are on. The connectors here are a pain - 2 9.5mm terminals so I has to buy a 4 way connector from revington so u could wire in alternator feed, feed to ignition switch and fuel pump. Quote Link to post Share on other sites
snowric Posted June 16, 2014 Report Share Posted June 16, 2014 Robin I will have a look tonight but from memory alternator feed (brown and white) comes in on left side and battery is on right side. Using water analogy when alternator is chagrin battery current flows across ammeter and deflects right towards the battery side. For the guy with the 45amp alternator I found that running th original with my 55amp resulted in a massive swing to the right as, following my usual good old crank to get started, the battery drew c 40amps. I didn't like this - having blown on ammeter and so I fitted a smith 60amp ammeter and have disguised it as a Lucas's using and old 30amp lucas innards - still wip as it is too bright when lights are on. The connectors here are a pain - 2 9.5mm terminals so I has to buy a 4 way connector from revington so u could wire in alternator feed, feed to ignition switch and fuel pump. Quote Link to post Share on other sites
peejay4A Posted June 16, 2014 Report Share Posted June 16, 2014 Kirchoff's Current Law explains why an ammeter will incorrectly show more charge current if a load is connected wrongly. Quote Link to post Share on other sites
joste Posted June 16, 2014 Author Report Share Posted June 16, 2014 thanks for the replies, Alan T has hit it on the head , it is hard over to the plus sign, thanks steve Quote Link to post Share on other sites
peejay4A Posted June 16, 2014 Report Share Posted June 16, 2014 If it's just started to do this it could be either the battery failing or the alternator output is uncontrolled. Can you measure the battery voltage when this is happening? Quote Link to post Share on other sites
RobinTR6 Posted June 16, 2014 Report Share Posted June 16, 2014 From memory I have one large brown feed (from alternator) and 2 brown and white , will check when I get hone. Quote Link to post Share on other sites
Guest ntc Posted June 16, 2014 Report Share Posted June 16, 2014 Brown and white large and small go on the right hand side when viewing from the front. Quote Link to post Share on other sites
AlanT Posted June 16, 2014 Report Share Posted June 16, 2014 The carbs were flooding and you got the car back. Does this mean its been to someone and been worked on? And before the ammeter was OK and you got it back and now its wrong. Is that whats happened? Quote Link to post Share on other sites
snowric Posted June 16, 2014 Report Share Posted June 16, 2014 ntc, my wires are the other way round....no doubt i put them back on wrong...deflects right when charging the battery and left when the battery is powering everything else ! Quote Link to post Share on other sites
AlanT Posted June 16, 2014 Report Share Posted June 16, 2014 So there is no charging going on? Somebody disconnected something. Quote Link to post Share on other sites
snowric Posted June 17, 2014 Report Share Posted June 17, 2014 yep - could the OP check the brown and yellow wire to the alternator is still plugged in (if they get no voltage on that line then there is no field to allow the alternator to work and the battery is just on full discharge for pump ignition etc.) Quote Link to post Share on other sites
peejay4A Posted June 17, 2014 Report Share Posted June 17, 2014 (edited) I could be wrong but I think that maybe the OP's original point is being lost. His problem seems to be high charge rate, not discharge. I suppose the field connection might have something to do with it but if the charge warning lamp comes on before starting and goes out when running it suggests not. Does it? Edited June 17, 2014 by peejay4A Quote Link to post Share on other sites
AlanT Posted June 17, 2014 Report Share Posted June 17, 2014 OP says his wires are reversed compared to ntc. So I guessed he had discharge rather than overcharge. But it was a guess. We don't really know yet. All we really know for sure is the meter is end-stop. We don't even know if someone else has fiddled about. Quote Link to post Share on other sites
RobinTR6 Posted June 17, 2014 Report Share Posted June 17, 2014 Guys, Neil, looks like I'm sorted. Two brown white on right, brown feed from alternator on left (when facing front of ampmeter), my mistake is I'd wired the third brown/white to the ampmeter when it should have been to ignition switch. It feeds the lights, so now have two brown/white on ignition switch and two on ampmeter. Now I get either an extra positive charge when lights on an engine running and extra negative when engine not running, as you'd expect. Thanks again, now off off a spin in the sun.... Quote Link to post Share on other sites
peejay4A Posted June 17, 2014 Report Share Posted June 17, 2014 OP says his wires are reversed compared to ntc. So I guessed he had discharge rather than overcharge. But it was a guess. We don't really know yet. All we really know for sure is the meter is end-stop. We don't even know if someone else has fiddled about. It was snowric who has his wires reversed. The OP hasn't mentioned it. Quote Link to post Share on other sites
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