Got a bad resistor

allenlane

Member
2N front mount with 12 v conversion. Received my brand spanking new resistor (static resistor p/n 8NE10306) not the variable one, and my multimeter shows it as 6 ohms. My coil is measures at 2.5 ohms, so I'll get a little over 1.5 amps to the coil with my alternator putting out 14.2 volts. I've spent more dang time with this stupid little ceramic blob. Anybody else get a bad one? I'm sure most of you guys are thinking I'm reading the reading wrong and the 6 is really .6, but I've triple checked it. I see now they have internally resisted 12 v coils, may go that route. One more question, if you send almost 6 amps to the coil, I know they will eventually burn up, but are they hot to the touch?
 
The fact you got a bad resistor isn't unusual. What is unusual is that you would use that resistor at all. You have a 12 volt coil. All you need is the oem ballast resistor. See tip # 30.

Keep coil current below 4 amps running and all will be well.
75 Tips
 
oem ballast resistor at 1.7 ohms hot, coil at 2.5 ohms = 4.2 ohms. 14.2 volts divided by 4.2 ohms gets you 3.38 amps. So why are you using any additional resistor?
75 Tips
 
I agree with Bruce on this one. 12V coil, OEM ballast resistor.
No need to mess with the extra connections to corrode and
cause problems. Not to mention the mounting and wiring ugliness.
 

The resistor that is 6 ohms is the ballast resistor that comes in the normal 12V conversion kit. That's the resistor p/n 8NE10306 mentioned above, and the only one in the system. Don't have 2, not sure why you guys assumed that.
 
(quoted from post at 01:16:56 01/28/18)
The resistor that is 6 ohms is the ballast resistor that comes in the normal 12V conversion kit. That's the resistor p/n 8NE10306 mentioned above, and the only one in the system. Don't have 2, not sure why you guys assumed that.
guess that you removed the original 12250 resistor?
those 10306 ceramic are well known to the community to have nearly random values all over the map. To be avoided at all costs.
 
" Don't have 2, not sure why you guys assumed that. "

Because the kits most always include that unneeded resistor and include instructions not to remove the oem ballast resistor, p/n 12250.

Regardless of what we assumed, all you need w/ that coil is p/n 12250. It will be .06 cold and 1.7 ohms hot, unlike p/n 10306 which will not change value as it heats up.
75 Tips
 
Bruce, you forgot that the resistor and coil form a voltage divider having the points at its junction; i.e., the resistor is in front of the points and the coil is after the points in the circuit. It's not a series resistance circuit with both resistances in front of the points, as your Ohm's law calculation assumes.
 
(quoted from post at 09:17:04 01/28/18) Bruce, you forgot that the resistor and coil form a voltage divider having the points at its junction; i.e., the resistor is in front of the points and the coil is after the points in the circuit. It's not a series resistance circuit with both resistances in front of the points, as your Ohm's law calculation assumes.
HHHAAAATTTTT???? :roll:
 
(quoted from post at 22:31:37 01/27/18)
(quoted from post at 01:16:56 01/28/18)
The resistor that is 6 ohms is the ballast resistor that comes in the normal 12V conversion kit. That's the resistor p/n 8NE10306 mentioned above, and the only one in the system. Don't have 2, not sure why you guys assumed that.
guess that you removed the original 12250 resistor?
those 10306 ceramic are well known to the community to have nearly random values all over the map. To be avoided at all costs.

I think is is much less confusing if we use pn's to discuss these resistors. Have to scratch my head a little as to why suppliers include the 10306 in the kit if not needed, but I do understand the logic. My tractor did not come with a 12250 variable resistor on it. My dad had started the conversion to 12V, but didn't commit to the need for a resistor, so it had everything but the 12250. If you google ballast resistor, you get all makes and models of resistors. Some static, some variable, ceramic and otherwise, so think we'll confuse folks less if we stick with pn's.


So I am going to add a 12250. From what I can tell it mounts on the back side of the dash under the ammeter on the "shelf" or curved portion of the dash. I don't have holes, so it appears i need to drill and tap two holes to accept the screws. The supplied screws do not appear long enough to put nuts on the back not to mention appearance. Sound about right?
 
If tapped mounting holes not present, someone must have covered/filled the factory holes, as all 9/2Ns had that resistor/terminal block.
 
(quoted from post at 10:44:32 01/28/18)
(quoted from post at 22:31:37 01/27/18)
(quoted from post at 01:16:56 01/28/18)
The resistor that is 6 ohms is the ballast resistor that comes in the normal 12V conversion kit. That's the resistor p/n 8NE10306 mentioned above, and the only one in the system. Don't have 2, not sure why you guys assumed that.
guess that you removed the original 12250 resistor?
those 10306 ceramic are well known to the community to have nearly random values all over the map. To be avoided at all costs.

I think is is much less confusing if we use pn's to discuss these resistors. Have to scratch my head a little as to why suppliers include the 10306 in the kit if not needed, but I do understand the logic. My tractor did not come with a 12250 variable resistor on it. My dad had started the conversion to 12V, but didn't commit to the need for a resistor, so it had everything but the 12250. If you google ballast resistor, you get all makes and models of resistors. Some static, some variable, ceramic and otherwise, so think we'll confuse folks less if we stick with pn's.


So I am going to add a 12250. From what I can tell it mounts on the back side of the dash under the ammeter on the "shelf" or curved portion of the dash. I don't have holes, so it appears i need to drill and tap two holes to accept the screws. The supplied screws do not appear long enough to put nuts on the back not to mention appearance. Sound about right?
The screw holes should be there. They were drilled and tapped in the brace.
Maybe they have the screws broke off in them?
I don't have a good picture of where it mounts but here's a bad picture.


9707.jpg
 
Bill, as one of us is misinformed, I thought a picture would best illustrate my comments. So I dug out an oem ballast resistor, p/n 12250 , along with a front coil. I measured the value of the resistor (.04) and the coil (.05). Then I ran a jumper wire between the resistor & coil. After accounting for the jumper wire resistance, I get .09 ohms. That would be the sum of the ballast resistor and the coil resistance.


Of course, after doing that, I remembered that I haven't figured out how to post a picture here since I refused to pay Photobucket $300.
75 Tips
 
Bruce did not forget anything and is correct in his calculation. Resistor, coil, and points are in series. The points do not connect at the junction of coil and resistor. Resistor connects to switch, other side of resistor to coil, other end of coil to points, and other side of points to ground.

Current path is from ground, through points (when closed), through coil, through resistor to switched power supply. When points are open there is no current flow
 
(quoted from post at 09:57:46 01/28/18) Bill, as one of us is misinformed, I thought a picture would best illustrate my comments. So I dug out an oem ballast resistor, p/n 12250 , along with a front coil. I measured the value of the resistor (.04) and the coil (.05). Then I ran a jumper wire between the resistor & coil. After accounting for the jumper wire resistance, I get .09 ohms. That would be the sum of the ballast resistor and the coil resistance.


Of course, after doing that, I remembered that I haven't figured out how to post a picture here since I refused to pay Photobucket $300.
75 Tips
never have to use any hosting site to post picture here, i go to the advanced posting tools i see below where i am now typing and click on upload photo, it opens a menu where you an choose photo then click on upload, then continue. the pictures do have to be pretty small tho.
9709.jpg
 
(quoted from post at 09:26:08 01/28/18)
(quoted from post at 09:57:46 01/28/18) Bill, as one of us is misinformed, I thought a picture would best illustrate my comments. So I dug out an oem ballast resistor, p/n 12250 , along with a front coil. I measured the value of the resistor (.04) and the coil (.05). Then I ran a jumper wire between the resistor & coil. After accounting for the jumper wire resistance, I get .09 ohms. That would be the sum of the ballast resistor and the coil resistance.


Of course, after doing that, I remembered that I haven't figured out how to post a picture here since I refused to pay Photobucket $300.
75 Tips
never have to use any hosting site to post picture here, i go to the advanced posting tools i see below where i am now typing and click on upload photo, it opens a menu where you an choose photo then click on upload, then continue. the pictures do have to be pretty small tho.
9709.jpg

I'll give it a shot. Problem is, 99% of my 8N pics aren't on the pc; they're on Photobucket. Maybe..........it's possible to dump them off of PB and back to the pc?
 
(quoted from post at 11:43:13 01/28/18)
(quoted from post at 09:26:08 01/28/18)
(quoted from post at 09:57:46 01/28/18) Bill, as one of us is misinformed, I thought a picture would best illustrate my comments. So I dug out an oem ballast resistor, p/n 12250 , along with a front coil. I measured the value of the resistor (.04) and the coil (.05). Then I ran a jumper wire between the resistor & coil. After accounting for the jumper wire resistance, I get .09 ohms. That would be the sum of the ballast resistor and the coil resistance.


Of course, after doing that, I remembered that I haven't figured out how to post a picture here since I refused to pay Photobucket $300.
75 Tips
never have to use any hosting site to post picture here, i go to the advanced posting tools i see below where i am now typing and click on upload photo, it opens a menu where you an choose photo then click on upload, then continue. the pictures do have to be pretty small tho.
9709.jpg

I'll give it a shot. Problem is, 99% of my 8N pics aren't on the pc; they're on Photobucket. Maybe..........it's possible to dump them off of PB and back to the pc?
I downloaded all my pictures off of PB when they got greedy.
 
(quoted from post at 11:53:31 01/28/18)
(quoted from post at 11:43:13 01/28/18)
(quoted from post at 09:26:08 01/28/18)
(quoted from post at 09:57:46 01/28/18) Bill, as one of us is misinformed, I thought a picture would best illustrate my comments. So I dug out an oem ballast resistor, p/n 12250 , along with a front coil. I measured the value of the resistor (.04) and the coil (.05). Then I ran a jumper wire between the resistor & coil. After accounting for the jumper wire resistance, I get .09 ohms. That would be the sum of the ballast resistor and the coil resistance.


Of course, after doing that, I remembered that I haven't figured out how to post a picture here since I refused to pay Photobucket $300.
75 Tips
never have to use any hosting site to post picture here, i go to the advanced posting tools i see below where i am now typing and click on upload photo, it opens a menu where you an choose photo then click on upload, then continue. the pictures do have to be pretty small tho.
9709.jpg

I'll give it a shot. Problem is, 99% of my 8N pics aren't on the pc; they're on Photobucket. Maybe..........it's possible to dump them off of PB and back to the pc?
I downloaded all my pictures off of PB when they got greedy.

I no longer see the option to download an album from photobucket, single pictures yes but no an album. To many people must have been doing just that. I know I did, not it is time to delete everything I have on photobucket and let them go away. I set up my own web page far cheaper that what PB wants to host pictures from.
 

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