[DeTomaso] Alternator swap, alternator indicator is on

Thomas Tornblom thomas at hax.se
Thu Jan 17 14:22:25 EST 2019

I've replaced the Bosch alternator in my GT5 with a 130A Ford style 
alternator from DB Electrical.

I just started it up to check that everything works, and while it 
charges, the alternator light doesn't go out, it just gets a bit dimmer.

Measuring the voltage on the wire to the light I see that it is around 
7V, which is about half of what the alternator outputs.

The stator wire should be around this voltage when the engine is running 
but I'm surprised that the indicator/ignition wire is at that voltage 
too. That seems wrong.

I know that there are owners who have replaced their old alternators 
with this type of alternator, how have you solved this issue? Skipped 
the light completely or did you not have this problem?

I'm contemplating adding a suitable zener diode in series with the wire, 
but it will take some testing to make sure that the current to the 
alternator then is enough to excite the field.

I'm also using this wire to engage the DRL:s, so hard wiring it to 
switched 12V will kill that functionality too.


Real life:   Thomas Törnblom             Email:    thomas at hax.se
Snail mail:  Banvallsvägen 14            Phone:    +46 18 32 31 18
              S - 754 40 Uppsala, Sweden  Mobile:   +46 76 209 8320

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