sentra Posted October 11, 2014 Share Posted October 11, 2014 So I had a new alternator with an internal regulator - installed it, ratio is 1:2. Car (for test purpose!!) is idling at 3500, which gives 7000rpm alternator speed. All connections good. start up - runs at 14.5v at the battery (sense wire looped back to post) As motor heats up - this diminishes back down to battery voltage only - about 11.9v. shiit. (Lamp does not come on) Take it back - run it on test bench. all works fine. Put it back in car - heats up and stops charging. shit. take it back - run it for extended period of time on test bench (at unknowen speed- well below 7000rpm). test fine. Alt idling temp ~75 deg. Test bench temp maby high 30's after extended period - but still charging correctly under load etc. Everyone shrugs, replaces regulator at a guess. Reinstall - same issue. Replace with new identical alternator - same issue. Resident autoelectrican background guy at work decides we should change to an external reg to eliminate heat as an issue - so we do. Same issue. Notes that when connecting 12v directly to feild that even with 10000rpm alternator speed we are only getting 13v and it should be >16. Any ideas as to what is going on here? Quote Link to comment Share on other sites More sharing options...
UTERUS Posted October 11, 2014 Share Posted October 11, 2014 Have you tried turning it off and on? edit: how new is your battery? does it start the car sweet or are you using jump pack? 1 Quote Link to comment Share on other sites More sharing options...
sentra Posted October 11, 2014 Author Share Posted October 11, 2014 have tried a brand new battery, have tried a brandnew battery jumped direct to Battery post and gnd. same behaviour. Quote Link to comment Share on other sites More sharing options...
cletus Posted October 11, 2014 Share Posted October 11, 2014 got a good earth wire on the engine? + wire big enough from alt to battery? Quote Link to comment Share on other sites More sharing options...
ajg193 Posted October 11, 2014 Share Posted October 11, 2014 Have you put an ammeter to it? See if something is loading it Quote Link to comment Share on other sites More sharing options...
UTERUS Posted October 11, 2014 Share Posted October 11, 2014 Have you put an ammeter to it? See if something is loading it This is not the thread for you, young grasshopper 3 Quote Link to comment Share on other sites More sharing options...
sentra Posted October 11, 2014 Author Share Posted October 11, 2014 huge cables on and off, good earth(s). no load. a point to note, when the motor is stone cold - i start it , 14.5, turn headlights on, it maintains 14.5. when it is hot, headlights on = <10v., Quote Link to comment Share on other sites More sharing options...
UTERUS Posted October 11, 2014 Share Posted October 11, 2014 IS the voltage drop binary or progressive? when cold to hot Quote Link to comment Share on other sites More sharing options...
sentra Posted October 11, 2014 Author Share Posted October 11, 2014 progressive as Quote Link to comment Share on other sites More sharing options...
ajg193 Posted October 11, 2014 Share Posted October 11, 2014 Okay cool, I'll stay shut up from now. Quote Link to comment Share on other sites More sharing options...
UTERUS Posted October 11, 2014 Share Posted October 11, 2014 progressive as Stock mazda alt or aftermarket? If aftermarket do you have a link handy to model. edit: is alt running A section belt or gillies Quote Link to comment Share on other sites More sharing options...
sentra Posted October 11, 2014 Author Share Posted October 11, 2014 gillies - its one of the one wire race type ones on trademe Quote Link to comment Share on other sites More sharing options...
Valiant Posted October 11, 2014 Share Posted October 11, 2014 I had similar problems with an alternator, it had a broken wire in the rotor up by the slip rings when it got hot it expanded, opened up the crack and stopped charging. It could be that they have a bad batch of alternators with poor soldering? 1 Quote Link to comment Share on other sites More sharing options...
sentra Posted October 11, 2014 Author Share Posted October 11, 2014 pooman helped the situation out by bringing some warm coronas around and doing some grunting. once again running with a separate(new) battery jumper-leaded to the alternator, and putting 12v direct on the feild, there is 16-17v coming out which it diddnt with the old battery, cool, great! when i then plug back on the (new-external) reg it goes down to 12.8, (the battery running the car ran out at this point and diddnt get to poke at it further) putting revs on diddnt increase regulated output and im starting to think rpm is a red hearring and that we have plenty asis. I need to verify the reg wiring in the morning. it is a mechanical type oem dx corolla unit and look at it after some sleep, i have another dx ingram after market unit, then i plugged it in, the fuse blew, hence being keen to re-look at the wiring, however at this hour it seems to be correct. 2 Quote Link to comment Share on other sites More sharing options...
Testament Posted October 11, 2014 Share Posted October 11, 2014 Are the big cables new for battery and engine ground etc? Old cooked/corroded/cracked or semi broken conductor that doesn't like heat maybe? Quote Link to comment Share on other sites More sharing options...
V8Pete Posted October 11, 2014 Share Posted October 11, 2014 I have a starter motor that refuses to starter motate when it's hot under the bonnet too. I don't understand it. Quote Link to comment Share on other sites More sharing options...
Poo Posted October 11, 2014 Share Posted October 11, 2014 I think you should change the pulley to a standard ratio and eliminate that. Also, warm Coronas are the best Coronas. Quote Link to comment Share on other sites More sharing options...
Poo Posted October 11, 2014 Share Posted October 11, 2014 Ps. It makes no sense, but give it a go maaayte. Quote Link to comment Share on other sites More sharing options...
77magnum13hundy Posted October 11, 2014 Share Posted October 11, 2014 oh i dunno how its wired but usually they have 2 other wires ones charge light the other is a 12 v ignition source(apart from the big batt feed), you dont need a charge light but its handy, but re-run the 12v wire directly from the key, this one switches it on or off. Its either that or its a faulty component in the alt. Quote Link to comment Share on other sites More sharing options...
h4nd Posted October 11, 2014 Share Posted October 11, 2014 Could you tell us the exact voltages in the system (incl decimal points) when the system is faulting please?, i.e. each end of the sense wire, and of the charge wire, and the battery. Ta Quote Link to comment Share on other sites More sharing options...
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