Ok folks here wots happening it driving me insane !

Mk2 orion, converted to turbo efi !

Car starts no problem at all, but wont charge until i rev it above 2500 revs, then when it charges it usually stays charging, occasionally at light etc it jumps back donw to 11.4 ish volts (approx) and when its reved again it charges fine.

I replaced the alternator, battery with brand new items, have tested earth and positive cables for resistance and all is fine, however the small blue wire that comes from alternator does not seem to go anywhere. I have done a continuity test on the blue wire to the earth terminal on the battery, and the same with the positive and nothing. (open circuit)
Also no battery light on dash. My question to you all is does this small terminal on the alternator with the blue wire control charging at idle revs? what should i be testing for next?

thanks Paul

 

Yes that blue wire is actually part of the charging circuit and NEEDS to be connected to the D+ terminal on the alt, it is the earth for the battery light, the power from which excites the field windings. When charging it becomes live and so two postives= no circuit thus extinguishing the bulb indicating all is well to the driver.

It will as you have found out if revved hard enough start charging until the engine is started again.

Martin

 

ok so as a temp fix to try it out without stripping out dash, could i attatch a wire from this alternator terminal to the neg battery and see if it solves the problem?

 

Nope no earth! It needs a positive feed to it, putting a direct live to it is not a good idea either, so best of just getting the light working or making your own temporary circuit with a bulb.

Martin

 

okay i see wot you mean now so basically the positive comes from the cluster through the dash lamp and out to the terminal on the alternator, which in turn is grounded at idle but when start turns to a positice putting out the dash lamp. i understand that but how does this affect the charge at idle?

 

the regulator on the alternator will cut out fella at idle, it needs the input ,test blue wire from alternator to dash clocks connection, on some of these there is a bullet connector on the passenger side under the radiator that corrodes

 

It dosen't, once it's started charging it will carry on until the engine stops, but you have to rev fairly high for it to start charging.

Martin

 

Once the engine is running touching a LIVE onto the "IND" terminal where the blue wire connects to is perfectly safe and ok, but no need just rev it and it will stay charging all the time until stopped as said.
tabetha