resistor needed in engine electrical system?
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Lead Driver
Joined: May 2000
Posts: 9,236
Likes: 12
From: Senoia, GA
ok, i think i have the idea figured out in my head. tell me if this is in the ballpark.
So the idea is that the coil will not run long on a full 12V, its too much. so you have to cut it down to about 9V. the coil will have some resistance naturally. the idea is to find out how much and then add an external resistor to make up the difference to attain the 3-4 voltage drop. and since ohms are directly constant with volts it measure out easily, V/I=R!
example: my coil measures 1.7ohms of resistance. i am looking for 3-4 ohms of resistance. 3 minus 1.7 is 1.3ohms. 4 minus 1.7 is 2.3ohms. so i need to find a resistor anywhere in the range of 1.3 to 2.3 ohms; which i did... a 1.6 from summit!
clear as mud?
-cutts-
So the idea is that the coil will not run long on a full 12V, its too much. so you have to cut it down to about 9V. the coil will have some resistance naturally. the idea is to find out how much and then add an external resistor to make up the difference to attain the 3-4 voltage drop. and since ohms are directly constant with volts it measure out easily, V/I=R!
example: my coil measures 1.7ohms of resistance. i am looking for 3-4 ohms of resistance. 3 minus 1.7 is 1.3ohms. 4 minus 1.7 is 2.3ohms. so i need to find a resistor anywhere in the range of 1.3 to 2.3 ohms; which i did... a 1.6 from summit!
clear as mud?
-cutts-
Cranky Old Guy
Joined: Mar 2008
Posts: 3,562
Likes: 6
From: Raphine, Virginia
Too early for math, but 1.4 was resistance of the stock wire. Unless you are ordering something else, NAPA should have a ballast resistor in stock and save the shipping. Advance/Autozone can't find their own rearend without their computer.
Thread Starter
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Lead Driver
Joined: May 2000
Posts: 9,236
Likes: 12
From: Senoia, GA
well there is a Summit store just down the road from me so i dont have to worry about shipping. i looked on napa's site but didnt see anything right off hand. 8.99 at summit for the resistor isnt too bad in my opinion!
thanks again for all the help guys!
-cutts-
. I need to close in on how I am going to fix the doors.
Posting Guru
Joined: Oct 2005
Posts: 1,017
Likes: 3
From: Longwood, Fl
Doors
Nope, not another thread-----yet! Just a quick comment after I finished the subject of this thread on that post. I noticed that several others on here have 72's. Until very recently, I had pretty well figured out what I was going to do to repair mine, with the exception that I had not figured out how to repair/replace the window frames (welded at the doors on the 72). One of the sites now has bolt on frames available---a meer $129.00 bux each. Still dont know the exact condition of the framework other than the doorskins on mine. BTW, your diagram looks like it came off of one of the sites tech articles----
.
You bet, I will be bugging the hell out of people for ideas when I get into my 72. Starting with Mig or Tig---. Wife dosnt know it yet, but I will be getting one or the other pretty soon----may need a place to stay
.
Also notice that no one has verified that the pertronix does not need a resistive source for the unit power, seems to be all about the coil.
Hope I didnt bust the thread with the doors thing. Hope no one got Mule-Lipped
.You bet, I will be bugging the hell out of people for ideas when I get into my 72. Starting with Mig or Tig---. Wife dosnt know it yet, but I will be getting one or the other pretty soon----may need a place to stay
.Also notice that no one has verified that the pertronix does not need a resistive source for the unit power, seems to be all about the coil.
Hope I didnt bust the thread with the doors thing. Hope no one got Mule-Lipped
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