trying to figure out an alternator issue...random voltage drops
09-07-2011, 11:26 AM
#1
trying to figure out an alternator issue...random voltage drops a year ago I switched to the 145amp truck alternator on my fbody.
a few weeks ago I installed a Holley EFI system in my car..
and of course theres no provision for running the alternator charge wire from it like the stock pcm does
so I found a thread that said something about using a 470 ohm resistor inline with any 12v signal
so I came off the fusebox, hit a 470 ohm resistor, and then into the alternator..
in the past few days I've noticed that my voltage Drops briefly for just a split second and then returns to normal....
doesnt seem to jive with anything specific as far as conditions go, Just appears very random
wondering if its an issue with the 470 ohm resistor trick I read that several people have said works to keep from frying an alternator...
would like to know if that is the right method for one, and if its not, then I would like to know the better method to use.
if its a voltage issue, I could always place a 5v regulator in line
Just want to know if my alternator issue is related to the way it is wired, and if there is a good solution.
Thanks.
a few weeks ago I installed a Holley EFI system in my car..
and of course theres no provision for running the alternator charge wire from it like the stock pcm does
so I found a thread that said something about using a 470 ohm resistor inline with any 12v signal
so I came off the fusebox, hit a 470 ohm resistor, and then into the alternator..
in the past few days I've noticed that my voltage Drops briefly for just a split second and then returns to normal....
doesnt seem to jive with anything specific as far as conditions go, Just appears very random
wondering if its an issue with the 470 ohm resistor trick I read that several people have said works to keep from frying an alternator...
would like to know if that is the right method for one, and if its not, then I would like to know the better method to use.
if its a voltage issue, I could always place a 5v regulator in line
Just want to know if my alternator issue is related to the way it is wired, and if there is a good solution.
Thanks.
09-07-2011, 01:37 PM
#2
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
I wonder why nobody's just made a damn single wire
or hot field "regular old" alternator for these cars. I
wonder if an auto electric shop could put old style
guts in a new style case.
or hot field "regular old" alternator for these cars. I
wonder if an auto electric shop could put old style
guts in a new style case.
Trending Topics
09-07-2011, 07:23 PM
#8
one wire coming out of the connector.. thats it...I just re-used my LS1 harness connector for the alternator..
It just needs a field coil wire to tell it to charge...and that one wire is the field coil wire...
I need to know what that field coil can have for the maximum voltage so I dont burn out the alternator...
they dont like to have Just a straight 12 volts...
I need to know what to do to make it happy..
with a 5v regulator in line fix the issue? or does it need more voltage than 5v to energize the coil to tell it to charge the system
It just needs a field coil wire to tell it to charge...and that one wire is the field coil wire...
I need to know what that field coil can have for the maximum voltage so I dont burn out the alternator...
they dont like to have Just a straight 12 volts...
I need to know what to do to make it happy..
with a 5v regulator in line fix the issue? or does it need more voltage than 5v to energize the coil to tell it to charge the system
Last edited by soundengineer; 09-07-2011 at 07:35 PM.
09-07-2011, 07:35 PM
#9
Well you need to google 1 wire.
the 1 wire is the one that goes to the battery to charge it. Any other wires running to the alternator it is not a 1 wire.
What I have told you I tried the resistor thing and it didn't work. Your local alt shop can convert it to a true 1 wire
Tim
the 1 wire is the one that goes to the battery to charge it. Any other wires running to the alternator it is not a 1 wire.
What I have told you I tried the resistor thing and it didn't work. Your local alt shop can convert it to a true 1 wire
Tim
09-07-2011, 07:40 PM
#10
I dont want to pull it to take it somewhere to convert it,
I want to use the thing as is...
what do I need to do since the 470ohm resistor trick doesnt seem to work...
I've asked the question plain as can be...
HOW MANY VOLTS IS IT LOOKING FOR ON THE FIELD COIL WIRE.
I know that 12 is supposedly too much... so what does it want...5v? 9v?
or can it be wired through one of the other pins to be able to use the standard 12v ignition on voltage?
I want to use the thing as is...
what do I need to do since the 470ohm resistor trick doesnt seem to work...
I've asked the question plain as can be...
HOW MANY VOLTS IS IT LOOKING FOR ON THE FIELD COIL WIRE.
I know that 12 is supposedly too much... so what does it want...5v? 9v?
or can it be wired through one of the other pins to be able to use the standard 12v ignition on voltage?
09-08-2011, 06:37 PM
#12
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
I've just seen stuff I don't understand about the "exciter" wire from
the PCM being a bag o' trouble. What its behavior (and misbehavior)
is, I dunno.
Maybe it's just a dumb remote sense / field power, or maybe the
regulator is in the PCM like in the olden days (remember the black
square can on the radiator support of 'pre-'70s cars?). Seems like
that would suit the control freak engine management types, to
give the PCM authority over system voltage. Who knows?
Maybe I should study up.
the PCM being a bag o' trouble. What its behavior (and misbehavior)
is, I dunno.
Maybe it's just a dumb remote sense / field power, or maybe the
regulator is in the PCM like in the olden days (remember the black
square can on the radiator support of 'pre-'70s cars?). Seems like
that would suit the control freak engine management types, to
give the PCM authority over system voltage. Who knows?
Maybe I should study up.
09-08-2011, 11:58 PM
#13
well...since nobody has a definite answer....
I'm still asking for somebody to chime in that does have a definite answer to what to do
I did find a set of instructions online that talk about one wire being a field wire that needs a resistor or a light bulb, and a differernt wire that could take just straight voltage..
I may just try moving the wire over and see what happens...
I figure worst case, I completely and instantly fry the regulator and need to replace it anyways..LOL
I may even just try a simple 5v regulator from radio shack to see if it will still charge off of that on the existing wire...
I'm still asking for somebody to chime in that does have a definite answer to what to do
I did find a set of instructions online that talk about one wire being a field wire that needs a resistor or a light bulb, and a differernt wire that could take just straight voltage..
I may just try moving the wire over and see what happens...
I figure worst case, I completely and instantly fry the regulator and need to replace it anyways..LOL
I may even just try a simple 5v regulator from radio shack to see if it will still charge off of that on the existing wire...
09-11-2011, 02:18 PM
#15
I couldnt for the life of me find that post...
I picked up a new alternator today as I'm sure my current one is Bad now...
and I wired up a 5 volt regulator to the circuit.
12 to pole 1, ground to pole 2, output from pole 3
up to 35 volts input, 5 volts regulated output...
should be fine...
and I just found something somewhere else that stated that the 145 amp truck alternator(like I am using) wanted 3-8 volts on that wire for the thing to charge..
tested it on the current alternator...
It charges... but its still doing the same thing...so I can only assume the alternator is gong bad from having 12volts on it with a 470 ohm resistor...
several people have still had issues with the 470 ohm resistor...and honestly, it makes sense as the voltage drop would be dependent on the rest of the circuit...meaning dependent on your actual alternator...and they are all different when you figure all the versions made for replacement parts.
09-11-2011, 04:46 PM
#16
Moderator
iTrader: (11)
Join Date: Mar 2002
Location: East Central Florida
Posts: 12,605
Likes: 0
Received 6 Likes
on
6 Posts
It could be that the problem is something like the block ground being bumped
by some electrical load (or load dump) and diverging from the battery &
sheet metal ground. The alternator reference ground is the block, through
the bracket and bolts. To the battery by traversing the block to the starter
ground cable on the other side, and to the sheet metal by those braids at
the back of the block. Not exactly ideal. If you can make the problem
persist with the old one, you might try taking off intra-alternator voltage
(stud to case) and see if it flickers the same way as PCM / IGN to sheet
metal. Maybe the gremlin lives in the suburbs.
by some electrical load (or load dump) and diverging from the battery &
sheet metal ground. The alternator reference ground is the block, through
the bracket and bolts. To the battery by traversing the block to the starter
ground cable on the other side, and to the sheet metal by those braids at
the back of the block. Not exactly ideal. If you can make the problem
persist with the old one, you might try taking off intra-alternator voltage
(stud to case) and see if it flickers the same way as PCM / IGN to sheet
metal. Maybe the gremlin lives in the suburbs.
