ALT dash light,excitor wire issues ?

[slydog 7,873]

So fitted the new ALT and it charged hard and well to 14.3v and by the time I got home it was only doing 13.2 and then no charge all after 1 drive.So I got a Bosch regulator for it and it charges,but only after a fair rev but only to 13.4ish. The out put doe's climb with RPM though up to over 14 around 2500rpm which is fine for me with the big 100mm GT pully. But that was as far as I was going in the shed with the car on the ground. Yes I was too lazy to put it on stands today.

 

So anyway after all this is said and done I can get it to charge after a rev but the dash ALT light never goe's out while the key is on and or the the car is running. I can prove it is charging but that dash light remains on ?  

 

So is there a issue with the cars wiring or is it a fault with the ALT as it never did this before. I can get the ALT light to go off via disconnecting the exciter wire on the back of the ALT but it will not charge. If I reconnect the wire the light comes on but it charges ?

 

Any ideas ??? 

[VDO 124]

What model Ford is it..?

[Thom 6,651]

XF ute

[VDO 124]

Sounds like the regulator is on the way out.  They're pretty cheap.

 

Here's a brand new complete alternator cheap.

 

http://www.ebay.com.au/itm/XE-XF-3-3L-4-1L-Ford-Bosch-Alternator-2-Year-Warranty-/141511277408?pt=AU_Car_Parts_Accessories&hash=item20f2babb60

[slydog 7,873]

Nope bruz...re-read the post

[gerg 10,871]

One of the rectifier diodes inside alternator might be stuffed.

 

Blown shunt resistor in your dash (if it has one) could also cause a dim glow when running, as instead of current flowing through it when charging, it goes through the globe only, which is in parallel. This seems more likely as when you rev the engine the volts come up, meaning the field becomes self-energising at that rpm. Below that rpm, instead of your field windings getting full volts through the shunt, they get fed only through the globe, which has voltage drop. Less volts to your field, less charge out.

 

Maybe connect a small jumper from + batt out to the field terminal and run it, check charge volts (to eliminate problems outside the alternator)

[slydog 7,873]

I hear what your saying and I'll check today but the lights is not dim...it is ON full tilt RED charging or not. Now it doe's have a larger than normal pully on it so I'd expect it to have less volts @ idle (850rpm) and the charge doe's come up with RPM but there is clearly a issue there even though the B/N true Bosch reg is allowing it to charge.

 

So just to get this straight the alt has one side of the windings @ full output constantly and only energizes both fields for charge out put thru the windings when it energizes the remaining side of the dash lamp/resistor ? So even though mine is infact charging and the light is still bright as the sun is on this New years morning (with my hangover about to go on full assault) there is a resistance issue in line somewhere not so much with the ALT that is not letting the light go out ?

 

Well thats sort of how I see it but don't exactly know the fix it of that just yet or the measuring to identify till my head is totally around this charging system. But If I find the constantly energized side of the globe I can trace the other side and check it for continuity and then resistance in ohms then try to energize it with 12volts to turn the light off.If that works then I'll be looking @ the ALT if it'd doesn't work (my guess is it won't) I'll be fixing the charge wiring.   

 

Thanks for the reply's guys...

[gerg 10,871]

Could also be a short in your field windings too

[slydog 7,873]

Installed a volt meter and disconnected the carb wire. Start it and rev and it starts charging.High 12's @ idle and 14 plus by 1800-2000rpm which is OK considering the big 100 mm pully.

[gerg 10,871]

Yeah that sounds right. Got me stuffed then.

[slydog 7,873]

I reckon it's the "cars" wiring more than the alt TBH...happy to be wrong but just the feeling I get from it.