Ignition Resistor

Ron7000

Member
There are many references to ignition resistor values but nothing indicating how to measure it. Is it measured with all connections in place
or with all removed.

If all removed what does it matter if the points are open or closed?

My 9N was running fine and then died like a blown light bulb. I suspect the resistor as there is no voltage to the coil.
 
Would not make any difference on the points. Using a volt meter or test light one side to ground and see where you loose voltage with the key turned on, my guess would be the switch.
 
Measure the ohm valve of a resister is done with wires unhooked. Not sure the reading you should get but it would be in the 1.5-3 or so ohm valve. Easy way to test things is a simple hot wire from battery non ground side to coil. If it runs hot wired problem is from the coil back if it doesn't run problem is from the coil to the distributor. I.E. coil points or other such thing bad dirty
 
I doubt if it is a resistor problem. If you mean the OEM Ballast Resistor, I'd ask if you are using the 6V/POS GRN setup or have you done a 12V switch out job, and if you have a n EI system installed? First, remove the battery, take it up to your local shop to be tested under load. If it fails to maintain a charge under load, invest in a good brand new one. While power is disconnected, begin tracing the entire wiring system. You will need to get a copy of WIRING PICTOGRAMS by JMOR as your roadmap guide. FACT: 99.98% of all non-starting issues are due to incorrect wiring regardless if 6V or 12V. A 9N means you have a front mount distributor. These must be rebuilt, timed, and tested off the tractor and on your workbench. Invest in a good brand of ignition points. Standard Ignition/Blue Streak, p/n FD-6769X are one of the few left that make good ones. NAPA sells them, avg cost = $16. Next is mounting and setting the timing per OWNER and I&T FO-4 Manual. Point gap is .015. Testing is performed per 75 Tips For N-Owners by Bruce(VA). The final step is mounting the unit back onto the tractor. The DIST must be set one correct way. If it gets forced down and is off 180 DEG, it will destroy the base unit at first power up. The cam on engine has an offset female slot. The DIST has an offset male tang. They must mate exactly. Regardless if you are using a 6V GEN or if it is a 12V ALT, you must have a fan belt tensioning device attached. Without proper fan belt tension, you will never charge the battery. Once your system has been correctly wired, then power is connected and you can further test a few things before starting up. Performing a true root cause problem solving method is the key to any problem. Don't guess.
 
Ron, It could be something as simple as a failed ignition switch, I would start tracing power from the battery through the system to the dist. first.
 
The oem ballast resistor? Or the white ceramic blob?

The oem ballast resistor should be .3 ohms cold, 1.7 ohms hot. Doesn't matter if it's connected or not; you are measuring ohms, not volts.

But it's highly unlikely that you have a resistor problem.

Put your multimeter on volts and start at the battery. 6.35 volts is fully charged. Look for that at the switch, resistor & coil ( if the points are open).
75 Tips
 
Forgot to mention that I disconnected the ignition switch and it tested OK. Also swapped battery from my NAA and same results. Resistor looks like the original from 1940 but may be better than new ones.
 
What is the voltage at the :

battery?

resistor?

coil?

Seems it would be easier to check that than to disconnect ignition wires and swap out a battery.
75 Tips
 
that one old guy that missed the value above often blurts out first thing that hits his mind, not even knowing what tractor is being asked about. Sure makes it difficult for those seeking accurate information and. Honest help. Nice to see people like you paying attention and providing real help.
 
(quoted from post at 21:49:29 06/12/22) that one old guy that missed the value above often blurts out first thing that hits his mind, not even knowing what tractor is being asked about. Sure makes it difficult for those seeking accurate information and. Honest help. Nice to see people like you paying attention and providing real help.


Must be that "LOGIC" folks take about...
 

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