idoari 10 Posted September 26, 2016 Hi, i have 80A mitsubishi alternator (A002T34591B which is probably the car's original, also apears in peugeot service box) most likely i have that much of current capability because i have A/C as stock on my 1.6 GTI. when i start the car the volage on the battery is 14.2v but after a few second it start to decrease to 13.9 - 13.7 when nothing working (light off , radio off... only the engine running) when i open the light it goes to 13.4v etc... i check all the wiring and the belt all fine. i have a new 60AH bosch battery (about 5 month old). i removed and cleaned the inside of the alternator cerfully (i took it apart and cleaned everything) the brushes seems a little worn down but still have "meat" on them the rear bearing is a little noisey and i ordered new one just in case but it has no play in it and i'm not sure if it cause this kind of undervoltage (maybe the voltage regulator is more likely??) i checked some of the diodes inside seems OK to me. do you think it's a problem or it still normal to get that kind of voltage? thanks Ido p.s. i also tried to raise the RPM and no major change. Share this post Link to post Share on other sites
jackherer 543 Posted September 26, 2016 Check the battery terminals and main grounds are in good condition. Also check the small exciter/battery light wire to the alternator. Does your battery light behave correctly? i.e. it should light up brightly with the ignition on and go off completely when the engine starts? 13.4v is not that low but obviously it shouldn't be dropping. A/C doesn't really use much electrical power BTW. Share this post Link to post Share on other sites
idoari 10 Posted September 27, 2016 The connections are clean and tight. The light is lit when the ignition is on and turn off when the car starts. The terminal for the light is connected to the alternator. It a\c compressor itself don't need any electric power to opreate BUT the compressor clutch IS. When the clutch engage it takes about 8A, just FYI ???? Check the battery terminals and main grounds are in good condition. Also check the small exciter/battery light wire to the alternator. Does your battery light behave correctly? i.e. it should light up brightly with the ignition on and go off completely when the engine starts? 13.4v is not that low but obviously it shouldn't be dropping. A/C doesn't really use much electrical power BTW. Share this post Link to post Share on other sites
toolie72 67 1 Cars Posted September 27, 2016 You will always get voltage fluctuations when putting on different loads (eg rear heated screen) Your battery is quite happy sitting at 12.7 volts so as long as its getting fed more than that with every load switched on, your alternator fine Remember as jackherer says to check all connections-a bad earth gives same symptoms as a component not working Share this post Link to post Share on other sites
jackherer 543 Posted September 27, 2016 When the clutch engage it takes about 8A, just FYI Wow, that's a lot! I always assumed it was a trivial amount but that is probably the same as having the headlights on full. Share this post Link to post Share on other sites
