[Mk2] [Turbo](help needed) new alternator but wont charge ?????

[mr2 import]

right just done the engine swap started fine after getting a air flow meter.the problem now is it wont hold charge for more than 5 mins?? and the alternator was only 3 month old which a took of my N/A. if the belt was on to tight would it stop the alt from charging?? the batt light comes on if the revs are below 1500rpm want the car on the road tonight if i can can any one please help me thanks oh and are the pulleys different on the N/A and the turbo alternators

[simmo490]

sounds like to me the pully on the alternator is too big mate, the smaller it is the more revs it does so less it neads to turn to charge,

check the pully size fella

[mr2 import]

is it a different size of pulley thats on the turbo alternator to whats on the N/A alternator ? cant see why as surely the crankshaft pully is the same size as the N/A and the batt seems 2 be ok. if left 4 5 mins it will start right up first turn!! want to drive it now but cant agghh!! oh yeh it the alt off of the old NA engine with the bracket off the old engine 2 if that helps!! geting really stressed out now

[andyjmr2turbo]

Use a voltmeter across the battery after you have started it... should be around about 14V from the alternator when charging... have you got any fault lights on the dash when the car is running ??

[simmo490]

you will be putting a partial charge in the battery, but as the pully is not small enought the alternator will not be doing enough RPM to charge properly

dave

[mr2 import]

yeh but av i have said after thinking bout it the pulley size wont matter as the crankshaft pulley is the same size as the N/A and the speed at idle is just the same so i can rule out the pulley size! the alt was new about 3 month ago and was working 2 weeks ago when i took the N/A lump out just cant C why it wont charge

[simmo490]

but the alternator wont just charge because it is spinning, it has alt sensing circut too, so when the alternator hits a certain rpm the sensing circut will tell it to start charging,

the crankshaft pully may be the same but if the alternator pully is bigger it will be spinning slower at idle, too slow for the circut to tell it to charge, hence why when u rev it up it senses it is spinning at the correct minimum speed and starts to charge

there is a reason people dont put NA alternators on turbos mate just not sure what them reasons are? maybe this is one

[mr2 import]

yeh a do know that mate i am a forestry engineer. so i do know about the exciter wire mate. all i want 2 know is are the turbo and N/A pulleys the same!!and the reason the N/A alternator was put on was because the engine i had didnt have 1 !! plus how will it be spining slower if the engine is runing at say 1200rpm on the turbo and say the N/A was at 1200rpm with the same size pulley ?? should still be charging tho right ??? dont mean to be blunt but am getting stressed out with it just want to go out and drive it

[simmo490]

um ok mr forrest lol OJ

both crankshaft pullys will be spinning the same speed but if the alternator pullys arw a different size the alternaors will run at different speeds, thats how fella, the smaller the secondary pully (alternator) the more revelutions spins

alo have you checked the 3 pn plug to the alternator, should be battery voltage at all 3 when ignintion is switched on (not running) somethimes one of the wires breaks between the alternator and the fuse box and halts charging

simmo

[simmo490]

oh and not sure on the pully sizes anyway mate, they could be the same, if so this is a pointless convo, jsut check the 3 wires

[mr2 import]

well a was looking 4 more help than that! all i want 2 know is if anyone has any other ideas of what 2 look at.anyone else had any probs with the charging system after doing a 3s-gte swap ??

[simmo490]

u checked them 3 wires mate?

[simo1973]

love this site lol

[mr2 import]

yeh

[simmo490]

glad to be of a service

[mr2 import]

i na bother mate!!!

[mr2 import]

right av been out and i think the alt is fooked checked the voltage at the batt and all it id doing is draining the batt .when i rev it the batt light goes out but it is still not charging the batt when its light and the batt has charged its self back up il start it up and see if im getting a charge coming from the alt! just cant see why its just stopped working on this engine when 3 weeks ago it was charging fine with no probs!! well looks like it another £170 down the drain lol of for a new alt the morn

[mr2 import]

right iv now dumped the mr2 alternator that was ment 2 be new and got one of another car works just fine now

[simmo490]

turbo on NA alternator??

[mr2 import]

N/A alternator !! works fine now