gas engine electrical questions
Grant Erwin
manual it says, "Beginning with engine serial number 3988441, the standard
wiring circuits of all 12 volt electrical equipment for Models TH, THD is
negative ground polarity instead of the previously furnished positive ground."
My engine is equipped with a generator (not alternator). It starts right up and
runs reasonably well (I'm about to do a tuneup) but the ammeter shows no
charging going on, and in fact I have to charge the 12V battery to run the
thing. The original mechanical voltage regulator has been replaced by a
solid-state kit which can be wired for 6V or 12V, negative or positive ground.
It is currently wired up for negative ground, and the negative battery cable
indeed goes to ground.
I am wondering a couple of things. First, according to the manual, my engine
should have a positive ground, not a negative ground. If a positive-ground
engine were connected as a negative ground, would the starter motor turn it
over backwards? If the field magnet were an electromagnet then it seems possible
that the polarity on the starter motor is irrelevant. I'm working on the
assumption that someone replaced the battery cables and rewired the thing for
negative ground by mistake, and that might be what's wrong with my charging system.
Also, assuming the manual is wrong about the ground polarity, is it possible to
bypass the (2 terminal) voltage regulator by simply jumping its terminals, to
see if the generator puts out current? If I'm thinking it through correctly,
this should apply full battery power to the generator's field windings, so it
should put out max power. I have learned the hard way to not just jump in
blindly and start shorting things, though - sometimes that leads to the magic
smoke escaping, and it's sooo hard to put back in. :-)
Thanks, Grant
Nadogail
Snag
Sounds like you might need to flash the field coils . Great thing about
generators , they don't care about polarity - as long as the field windings
have the correct magnetic polarity to match the reg and battery hookup .
--
Snag
every answer
leads to another
question
Grant Erwin
corresponds to a six volt positive ground generator. So the answer to why
the charging system isn't charging is simple: someone swapped the system
over to negative ground, put in a 12V battery, but left the generator alone.
It stands to reason that a 6V generator doesn't have much of a chance charging a
12V battery.
More worrisome, the manual says:
"The wiring diagram, Fig. 18, illustrates a negative ground circuit. If polarity
of generator is for a positive ground circuit, terminal connections at ammeter,
ignition coil, and battery are reversed from those shown. DO NOT use positive
ground generator and regulator in a negative ground circuit, or vice versa.
Polarity does not affect starting motor, coil, and distributor."
So now the question shifts to: since my engine has been wired up backwards for
at least a decade, is there any hope of making the generator generate again,
assuming I rewired the system and battery to 6V positive ground again?
Grant
Pete C.
Grant Erwin wrote:
>
> Followup: I got the numbers off the Autolite generator (GAS 4305) and this
> corresponds to a six volt positive ground generator. So the answer to why
> the charging system isn't charging is simple: someone swapped the system
> over to negative ground, put in a 12V battery, but left the generator alone.
> It stands to reason that a 6V generator doesn't have much of a chance charging a
> 12V battery.
>
> More worrisome, the manual says:
>
> "The wiring diagram, Fig. 18, illustrates a negative ground circuit. If polarity
> of generator is for a positive ground circuit, terminal connections at ammeter,
> ignition coil, and battery are reversed from those shown. DO NOT use positive
> ground generator and regulator in a negative ground circuit, or vice versa.
> Polarity does not affect starting motor, coil, and distributor."
>
> So now the question shifts to: since my engine has been wired up backwards for
> at least a decade, is there any hope of making the generator generate again,
> assuming I rewired the system and battery to 6V positive ground again?
The simple solution when dealing with old charging stuff like this is to
just stick a more modern car alternator with integral regulator (often a
"one wire" type) on in place of the old stuff and be done with it. $40
at a salvage yard and an hour of work retrofitting is usually all it
takes.
Grant Erwin
Can't do it this time, Pete. The distributor mounts on the generator ..
The wiring diagram for my engine is:
http://www.tinyisland.com/images/temp/wisconsinFig18.jpg
GWE
cl...@snyder.on.ca
<grant...@kirkland.net> wrote:
>I have a Wisconsin THD 18hp gas engine. It has serial number 2942748. In the
>manual it says, "Beginning with engine serial number 3988441, the standard
>wiring circuits of all 12 volt electrical equipment for Models TH, THD is
>negative ground polarity instead of the previously furnished positive ground."
>
>My engine is equipped with a generator (not alternator). It starts right up and
>runs reasonably well (I'm about to do a tuneup) but the ammeter shows no
>charging going on, and in fact I have to charge the 12V battery to run the
>thing. The original mechanical voltage regulator has been replaced by a
>solid-state kit which can be wired for 6V or 12V, negative or positive ground.
>It is currently wired up for negative ground, and the negative battery cable
>indeed goes to ground.
>
>I am wondering a couple of things. First, according to the manual, my engine
>should have a positive ground, not a negative ground. If a positive-ground
>engine were connected as a negative ground, would the starter motor turn it
>over backwards? If the field magnet were an electromagnet then it seems possible
>that the polarity on the starter motor is irrelevant. I'm working on the
>assumption that someone replaced the battery cables and rewired the thing for
>negative ground by mistake, and that might be what's wrong with my charging system.
A series wound starter motor will turn the right way regardless which
way it is wired. There are two types of generators - internally
grounded and externally grounded Internally grounded generators
require an alternator that feeds the feild. Externally grounded
generators require a regulator that grounds the feild. The right
regulator is required - wrong one will NOT work. Then the generator
needs to be "flashed" to magnetise the feild poles the right way so
the residual magnetism will "kick-start" the generator. On an
internally grounded unit you disconnect the reg from the feild
terminal and momentarily short the feild terminal to the battery
positive.
cl...@snyder.on.ca
On positive ground the coil SHOULD be reversed. Reverse coil polarity
CAN cause hard starting
Pete C.
You may not be able to remove the old generator in this case, but you
can most likely bypass it and hang a new alternator elsewhere. Once for
a small car will be pretty compact.
Grant Erwin
True. I could make a bracket which put the alternator's pulley inline
with one of the 3 belts which go between the gas engine's drive sheave
and the air pump's driven sheave. That's not a bad idea. I suppose something
like an alternator from a '78 Chevy truck would work, eh?
Grant
Pete C.
On my '70s Deere 500C backhoe which originally had a 55A Motorola
alternator with external regulator, I just replaced it with a $25
salvage '90s Delco CSxxx alternator. In my case it fit the mounting
bracket directly and all I had to do was take the serpentine belt pulley
off the Delco alternator and bore and fit the double V belt pulley on in
it's place.
Grant Erwin
Yup. Mine isn't set up for a belt-driven unit - the generator it's fitted
with is gear-driven. So anything I retrofit has to include a way to drive it,
ergo stealing some drive off the main belts.
Grant
oldjag
If it helps space wise, I grabbed a alternator from a Suzuki Samuri,
it's about the size of an orange, but puts out 45 amps as I recall,
and uses an internal regulator. I use it on my 67 E type race car to
save weight and keep the distributor-less ignition and electric fan
happy. Beats having to charge the battery between races....
Grant Erwin
> If it helps space wise, I grabbed a alternator from a Suzuki Samuri,
> it's about the size of an orange, but puts out 45 amps as I recall,
> and uses an internal regulator. I use it on my 67 E type race car to
> save weight and keep the distributor-less ignition and electric fan
> happy. Beats having to charge the battery between races....
Was it complicated to wire up? I was thinking of one of those GM one-wire
alternators, purely for simplicity of wiring .. this machine doesn't have
an idiot light, but it does have an ammeter.
here's the circuit:
http://www.tinyisland.com/images/temp/wisconsinFig18.jpg
Grant
Bill Noble
"Pete C." <aux3....@snet.net> wrote in message
news:4a402173$0$30277$ec3e...@unlimited.usenetmonster.com...
Nonsense - the simple solution is to repolarize the generator and move on
with life - I switched my morgan from pos to neg ground by just swapping the
battery around and repolarizing and all is well - of course the ammeter read
backwards but that isn't a problem - you can't do this with an alternator,
but it works fine with an old style generator
spaco
problems to a place in mpls mn called Schelin Electric. They always
have the solution.
Pete Stanaitis
--------------------
Pete C.
In my case since I was replacing an alternator, all the connections were
already there. The big B+ charge terminal to the battery, ignition
switched batter connection for the field terminal and the connection for
the indicator light. The one wire types make it that much simpler,
connect it to the battery and you're done.
One thing to be careful of would be your ammeter since a more modern
alternator should have a much greater amp capacity than the old
generator.
Pete C.
His regulator is not an original mechanical type, so it will not just
swap around. The regulator is probably also undocumented and
unsupported.
Bruce L. Bergman
<grant...@kirkland.net> wrote:
>
>> If it helps space wise, I grabbed a alternator from a Suzuki Samuri,
>> it's about the size of an orange, but puts out 45 amps as I recall,
>> and uses an internal regulator. I use it on my 67 E type race car to
>> save weight and keep the distributor-less ignition and electric fan
>> happy. Beats having to charge the battery between races....
Hmmm. Have to remember that one for my Honda Odyssey FL350 - I have
the stock lighting coil loaded to the max with two driving lights
(Unity hose lights) and a set of Fiamm electrtic horns. (Wired
through an alternating flasher for Hi-Lo.) Now to find a place to
hang it and put on a crank pulley...
>Was it complicated to wire up? I was thinking of one of those GM one-wire
>alternators, purely for simplicity of wiring .. this machine doesn't have
>an idiot light, but it does have an ammeter.
>
>here's the circuit:
>
>http://www.tinyisland.com/images/temp/wisconsinFig18.jpg
>
>Grant
All the charge light circuit requires is a panel lamp holder with
the right size bulb, one side goes to ignition and the other to the
alternator sense lead to tell the field to turn on. Or you could use
a red clearance/marker light, as long as it's isolated ground.
Worked the same as older Generator cars with a sense lead to the
regulator. Came on just fine on the early Corvair with the late model
alternator conversion - I have a Sonalert in parallel with the lamp
for "The Fan Belt Just Broke/Jumped, Dummy!" duty.
You might need to add a diode in series if the pilot lamp supplies
reverse power to the coil - if you turn off the ignition and it keeps
running till you pull the Charge lamp, that's why.
--<< Bruce >>--
Chas
"Bill Noble" <nob...@nowhere.invalid> wrote in message
news:h1pt4e$29t$1...@news.eternal-september.org...
If you wish to have the ammeter reading correctly, just swap the two wires
on the terminals of the ammeter.
--
Regards,
Chas.
(To email me, replace "xxx" with letters tango papa golf.)
Bill Noble
"Chas" <uml...@xxx.com.au> wrote in message
news:4a41f8d4$1...@dnews.tpgi.com.au...
>
> "Bill Noble" <nob...@nowhere.invalid> wrote in message
> news:h1pt4e$29t$1...@news.eternal-september.org...
>>
>>>
>>> just stick a more modern car alternator with integral regulator (often a
>>> "one wire" type) on in place of the old stuff and be done with it. $40
>>> at a salvage yard and an hour of work retrofitting is usually all it
>>> takes.
>>
>> Nonsense - the simple solution is to repolarize the generator and move on
>> with life - I switched my morgan from pos to neg ground by just swapping
>> the battery around and repolarizing and all is well - of course the
>> ammeter read backwards but that isn't a problem - you can't do this with
>> an alternator, but it works fine with an old style generator
>
> If you wish to have the ammeter reading correctly, just swap the two wires
> on the terminals of the ammeter.
> --
> Regards,
>
> Chas.
>
dodge - it's not important so long as you know it's reversed