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Alternator switched feed from coil supply
davidimurray - 29/12/14 at 06:29 PM

Fitting a little denso alternator to the duratec. The alternator has a battery connection, then a sense, switched live and ignition light connection. Sense will be across to the battery terminal and ignition is the old setup from the old alternator. I need to find a switched live connection and it just happens that my ford coil pack is next to the alternator.

Any reason why it's a bad idea to use the 12V supply to the coil and tee off it to the alternator?

19sac65 - 29/12/14 at 06:57 PM

I would personly give it its own feed - they may interfere with each other
Also,i used the battery terminal for the sensor wire and it flattens the battery over a couple of weeks
Ime going to connect it to the switched terminal over the winter,or do away with it completely

davidimurray - 29/12/14 at 07:17 PM

Thanks for the tip of the sense wire. will connect mine to the switched live.

Just rechecked the wiring in my car and remembered that because I have a hard rev limiter fit the 12v can be cut.

Looks like the next easiest place to get to is from the 12V supply to the ignition light.

Chris_Xtreme - 30/12/14 at 05:50 PM

If I am right in thinking you need the sense wire as without it, the alternator wont switch on charging as such.

I had the same problem when I bought my car, it was wired straight to the battery and it would flatten in a day or 2. needs to be ignition switched.

davidimurray - 30/12/14 at 07:55 PM

quote:
Originally posted by Chris_Xtreme
If I am right in thinking you need the sense wire as without it, the alternator wont switch on charging as such.

I had the same problem when I bought my car, it was wired straight to the battery and it would flatten in a day or 2. needs to be ignition switched.


Thanks Chris

Have you made this mod to your wiring and has it cured the problem?

Cheers

Dave

Chris_Xtreme - 30/12/14 at 09:26 PM

yep - it def did stop the battery going flat.

the way I proved it was to get an ammeter, pop it between all the wires that connect to positive on the battery (with the key out!) and i removed each one until I knew which wire was the problem.. the sense on the alt. It will draw all the time.

I think I put it on the main beam fuse, this only (on my car) goes live when the ignition is on. It only draws a couple of amps until the car is running, then when the alt gets charging nothing goes on on this wire.

these may help: (there are many posts on here about the denso) also it may vary depending on how many connections you have, I have three. I think you said 4, but the sense one i believe still behaves the same.

http://www.locostbuilders.co.uk/viewthread.php?tid=158490

http://westfield-world.com/daihatsu_alternator.html

cheers

[Edited on 30/12/14 by Chris_Xtreme]

The Black Flash - 2/1/15 at 01:16 PM

quote:
Originally posted by Chris_Xtreme
If I am right in thinking you need the sense wire as without it, the alternator wont switch on charging as such.

I had the same problem when I bought my car, it was wired straight to the battery and it would flatten in a day or 2. needs to be ignition switched.


That's weird - I've got a denso (3 pin) and never wired up the sense (switched live) as I couldn't find a definitive answer (and there wasn't a convenient wire to take it from). There have been a few threads on it but no-one seems to know for sure. Anyhow, mines now done over 1000 miles and the charging voltage has always looked ok, so I can only assume it's not needed.