Having To Fit An Alternator Back To The Race Pug

[wardy18 33 1 Cars]

I think you've got it sussed yeah!

 

cut-off needs to be between the main live terminal and the rest of the system, normally its in the main line to the starter/alternator and the wire to the shunt box as well.

 

fine job, so ill change the isolator switch to run between my battery and the power block i have that everythin screws into for power, the alternator will still be directly to the positive side of the battery but the wire coming from the battery to power everything on the car will be isolated before the power to gets to anything on the car

 

this should work yeh??!

[Rob Thomson 6]

Yep, a bulb spliced into that wire. You need a 12v bulb in the order of 1-5w. I would have thought any warning lamp from Tweeks would do the trick. You could substitute the bulb for a resisitor, but I couldn't tell you what rating that should be...

 

If you want to get it going in a hurry you could use a side-light bulb or something of that nature.

[jackherer 543]

You need a switch like this:

 

 

wired like this:

[wardy18 33 1 Cars]

oh and i have no dashboard whatsoever, just a few guages in a small box ontop of the steering column so i would need to buy and aftermarket bulb and fit it into the box

[wardy18 33 1 Cars]

You need a switch like this:

 

 

wired like this:

 

would it be easier for me at the moment to just change the Isolator switch to run in the positive lead from the battery and then wire in a resistor or bulb inline the Alternator Excitor wire

 

i assume this bulb or resister just drains any excess power the runs from the ignition switch before it gets to the alternator to save it burning out the alternator

[jackherer 543]

The resistor with the kill switch is nothing to do with the resistor/bulb for the alternator. TBH I am not quite sure what the kill switch resistor does.

[wardy18 33 1 Cars]

i think as long as the power source throu the wire to the alternator is cut off as soon as i flick the ignition switch off then i probably wont need anything else apart from this bulb inline too and once ive changed the isolator to run in the positive wire my problems should be sorted

 

does this sound like the best plan, please let me know if you think i should be doin somethin else

[wardy18 33 1 Cars]

hi again

 

ok so ive changed the isolator switch into the positive wire and the shut down is much more responsive (without the alternator connected that is)

 

this however hasnt solved my problem (i havent fitted the bulb inline with the exciter wire yet but i do have one) the car was running with the alternator charging the battery, i then flicked the isolator switch to turn it off and it stayed running, flicked off the ignition switch and the fuel pump and it all kept running

 

i then went to the alternator with the car running and all this switched off, i pulled off the excitor wire from the alternator and the car shut down as it should have

 

so why is this excitor wire keepin the car running

 

my ignition switch is wired with one terminal having wires to the coil/excitor and power to the fuel pump switch and the other terminal to ground

 

im thinkin that because the excitor wire and the coil wire are on the same terminal that for some reason the excitor wire is feeding power to the coil wire even when the battery is disconnected!!!!

 

i assumed the alternator used the power from this wire to excite it and so not return any to the ignition switch

 

do i need an ignition switch with seperate terminals for the excitor wire and coil wire?!

 

hope u understand what i mean

[welshpug 1,622]

have you got a resistor or a bulb inline with the excitor wire yet? a sidelight/side repeater or something similar should be sufficient.

 

does it happen with the wire disconnected?

[wardy18 33 1 Cars]

no i have bought a 12 volt warnin light like you said but am yet to fit this to the excitor wire

 

as soon as the excitor wire is disconnected from the alternator everythin is back to normal working order apart from the fact that the alternator is no longer charging the battery

 

what do you reckon mate?!

[Rob Thomson 6]

so why is this excitor wire keepin the car running

Because you haven't got a bulb in it...!

 

When the alternator isn't running the connector that the excitor wire is connected to is essentially grounded. Hence why the bulb glows (or would if you had one); you've got +12V at one end of the wire and 0V at the other. When the alternator is working you get +12V at the connector, which is why the bulb then goes out cos you have +12V at both ends and thus no current between them.

 

What you're doing when you cut your battery switch is connecting your coil straight to the +12V feed from the alternator excitor connection. A bulb will stop that happening.

[jackherer 543]

Fit the bulb to the exciter wire so your alternator works properly then fit a proper fia cutoff switch like the one I posted above that cuts the ignition live from the coil. Basically if your alternator is working properly the engine will run on if you only disconnect the battery which is why you need to cut the ignition too. The fia switches are designed for this very purpose.

[wardy18 33 1 Cars]

ok guys before i got the replies i thought i would trust your words and go and fit the bulb and sure enough as you have now said above it all works

 

this is what i wasnt sure off before and what i trying to get at when i was asking why i needed the bulb

 

i must apologise as i should have done what u said to start with, i just didnt quite understand why but now i do

 

its all workin great now so thanx alot for all your help and sorry for being a bit thick