Diode or 5watt light

8nRookie

New User
Ok being some what mechanical incline. I bought a 48 early 48 front mount distributor. The person or persons have started a 12v conversion. And several parts were stolen or just gone. I have the alternator and distributor base. Bought cap and 12v coil, now rewiring oh I was told the coil does not need the resistor/resistors in all diagrams I have seen. Any way question is the 50v 1amp diode in alternator line # 1or the option of a 5watt light, why would the light work? Is the light going to stop the feed back of voltage thru the alternator and why would it work. Not an electrician by far.
 
Either the diode (cathode to #1) or the light is wired to the ignition switched +12V.
The light illuminates when the ignition switch is turned on before engine start due to the absent field winding voltage that allows a current path to excite the field winding. The diode would also have a current path into #1 to excite.
Once the engine is started the stator winding will immediately generate voltage due to the pre-energized rotating field which then evens out the voltage level at #1 compared to the ignition switch, therefore light out or diode gets back biased or zero current.
Either way when the ignition is shut off, no worries about any leakage current, none there.
Greg
 
Thanks for the explanation. The way I was told it was like a leaking faucet and burn out coil and/or points.
 
Ok thanks the one on it is gone so I will pickup a new one now do I also need the ceramic one ? Would it help or not, this resistance to coil is giving me a headache. I understand what it does but testing it does not come out to any of the values that are posted. When I tested the coil points spring to distributor tab I show 8 ohms, in my mind that would be higher resistance and with the add OEM at .6 would higher the resistance which in results of a weaker spark. Does this sound right or is it the fool with a bad multimeter.
 
" do I also need the ceramic one ? "

No.

As I said in tip # 30: " You can use the 6-volt coil with an additional external resistor, but most folks do not have the time or interest to accurately measure coil resistance to determine the necessary value of the additional resistor. (You always need the OEM ballast resistor with a front coil even if you use a 12 volt coil) "

You are having the problem I described.

You are measuring the coil incorrectly. Measure primary circuit resistance, post on the top to pigtail on the bottom.

A 12v front coil should be 2.5 ohms. Use 1 ohm for the value of the oem ballast resistor to get a total of 3.5 ohms needed to reduce running current to less than 4 amps.
75 Tips
 
I have read all the tips and have a link to them for further assistance. When I get a chance I am going to recheck coil (OCD) haha!!! I picked up this 8n for less than 1k. I am not going to do a show restoration but get it looking nice and use around the house. Needs work and gives me something to do.
 
(quoted from post at 08:34:02 02/20/18) Thanks for the explanation. The way I was told it was like a leaking faucet and burn out coil and/or points.
on't listen to that person anymore!
 
JMOR was commenting on my quote not your explanation. That?s why things get distorted and threads go haywire. Everything is cool and thanks for all the info.
Oh BTW since I have not got it running and I have service and parts manual. I can?t find what the pull cable is that comes out the top of trans. Looks like PTO knob on a dump truck.
 
?Any way question is the 50v 1amp diode in alternator line # 1or the option of a 5watt light, why would the light work? Is the light going to stop the feed back of voltage thru the alternator and why would it work. Not an electrician by far.?


On a Delco 3 wire alternator, #1 pin is for an excite, start up, or kickstart voltage. It is only required momentarily to turn on the regulator to start the alternator to charging, then internal diode trio supplies voltage to operate the regulator.

A problem comes when the switch is turned off to shut down the engine. The power from the diode trio is connected to Pin #1 and feeds back to the output of the switch and on to the coil allowing the engine to continue running when switch is off.

A diode is a one way device that allows forward current to start the alternator but blocks reverse current to the coil so the engine shuts down.

A light passes a very small current (1/4 to 1/3 amp) to start the alternator, but is nowhere near the approximately 4 amps needed to operate the ignition so the engine shuts down when switch is turned off.

Neither device has anything to do with back feed once switch is turned off and engine shuts down.
 
That is what I was wondering what the difference was, kind of figured it but your explanation confirmed my thoughts. Now I understand it
Thanks
 
(quoted from post at 09:53:05 02/20/18) JMOR was commenting on my quote not your explanation. That?s why things get distorted and threads go haywire. Everything is cool and thanks for all the info.
Oh BTW since I have not got it running and I have service and parts manual. I can?t find what the pull cable is that comes out the top of trans. Looks like PTO knob on a dump truck.

Top of trans? Got any pictures of that? It may be an aux trans that is in front of the trans,
 
Yes but don?t know if it will go thru on forum. I?ll try
Cable is right by throttle linkage
a257751.jpg
 
(quoted from post at 12:29:48 02/20/18) Yes but don?t know if it will go thru on forum. I?ll try
Cable is right by throttle linkage
a257751.jpg

looks like Sherman stepup trans cable. cable may be frozen in place. check out the link

http://www.oldfordtractors.com/sherman.htm
 
Thanks for the link. That helped tremendously. Now I need to
get it running to see if it?s a step-up or more perfect would be
a step-down. That info made my day.
 

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