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Old 08-25-2015, 10:06 AM   #1
Capt Kirk
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Default Another coil resistor question

Awhile back I was working on my helmet distributor. The work I did helped but the car still wasn't completely right. I checked voltage at the coil and, if I remember, it was somewhere between 2 and 3 volts. This prompted me to check the coil resistor. It had obviously been pretty hot and the phenolic rod supporting the wire coils was broken in half. I ordered a whole new assembly from Mac's (p/n 32-14615-1) that they indicate is the correct part for my 35 Cab. The description of the part says 20-30 amp. Mac's also has just the resistor (not the whole fuse assembly) which is p/n 32-11948-1 which is indicated at 40 ohm.
Anyway, I installed the new assembly and started the car and let it idle in the driveway. Within a few minutes when reentered the car there was some visible smoke...a pretty strong electrical smell and it was obvious that the resistor was way hot. I shut the car off for fear of a fire. Within the short time I ran the car the center section of new phenolic rod was scorched black. Is this normal??
I reviewed some old threads on the issue and I see that the coil should be 1.3 ohm and the resistor somewhere between .6 and .8 ohm...is this correct?
Why on earth would Mac's be saying a 40 ohm resistor is correct for my car? Is there a source where I can get the correct resistor? I'm expecting my rebuilt coil back from Skip any day now and would like to have the correct resistor in place before I install it.
Kirk
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Old 08-25-2015, 10:54 AM   #2
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Default Re: Another coil resistor question

I just posted how to repair the original resistor within the past two weeks, look it up.
The old original is better than a new one. G.M.
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Old 08-25-2015, 11:35 AM   #3
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Default Re: Another coil resistor question

G.M.
I found your post. The problem is that the resistor I recently replaced was a newly purchased resistor back when I restored the car and now the rod that the resistor wire is wrapped around is broken in half. I do, however, have the broken one back in the car since my recently purchased Mac's resistor was getting scary hot and I didn't want to start a fire. My coil is still at Skips so I'm not going anywhere for awhile.
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Old 08-25-2015, 11:42 AM   #4
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Default Re: Another coil resistor question

Cap'n, the resistor does get hot normally. It's function is to smooth out the voltage delivery to the coil at just below 4 volts. The more voltage the resistor sees, the hotter it gets.
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Old 08-25-2015, 01:34 PM   #5
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Default Re: Another coil resistor question

I use that part from Macs every so often. The spec of 40 ohms is very wrong and they do get very hot the first few times they are ran. The spec should be .6 to .8 ohms .
Smoke is normal hee as well ....
Did ya happen to check the voltage at the coil with the new ballast......??
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Old 08-25-2015, 02:00 PM   #6
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Default Re: Another coil resistor question

The voltage at the coil seemed ok...if I recall it was about 3.5 which was higher than the old ballast. The stink and smoke had me so concerned that I immediately shut it off. If it's normal for a new ballast to stink and smoke for awhile when new then I'll be a little more comfortable putting it back on and riding it out a bit longer. Am I correct in thinking that a "never been rebuilt" coil can cause added resistance resulting in a hotter than normal ballast? I know the coil was on it's way out because I'd have to do the "dance"...drive for a bit...wait for 20 minutes...drive for a bit.
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Old 08-25-2015, 02:34 PM   #7
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Default Re: Another coil resistor question

Actually " added " resistance wont hurt any thing other than less spark.
Its when resistance drops that things get hot pretty quick and the current increases...
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Old 08-25-2015, 05:06 PM   #8
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Default Re: Another coil resistor question

Thanks Bubba...you've always been a wealth of knowledge for me. Once I get my coil back from Skip, I'll put the new resistor back in and measure some voltages. I wanted to check here before possibly putting a potentially faulty resistor back in and taking a chance of ruining a newly rebuilt Skips coil or worse yet...starting a fire. Whenever I see smoke and smell electrical in a vehicle...I kinda get nervous! I'll follow up with this thread once I get it all back together. Thanks again!
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Old 08-25-2015, 06:10 PM   #9
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Default Re: Another coil resistor question

A year ago or so I had to work on a car that just had a new Macs resistor, it got hot started smoking ---smelled like a 3rd world brush fire, the core the wire was wrapped on was bamboo -as it cooked up the screws got loose and it went open--put in a NOS Ford one, no more problem ---the GYP part was held together with wood screws, the resistor wire was just caught between the metal and wood
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Old 08-25-2015, 07:01 PM   #10
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Default Re: Another coil resistor question

Kurt...sounds like my experience. When I opened the door I thought something was on fire in there and the electrical smell was almost overwhelming. My "core" also looks like bamboo but I'd guess it's not?...maybe 3/8" in diameter and bamboo colored and...yes, screws in the ends. I don't have a NOS Ford one...I have an identical one that I put on when I restored the car years ago and the "bamboo" was broke in half. I see that Auto Zone sells something that looks like it would fit wound over a porcelain rod. I didn't see any info regarding resistance so I was reluctant to buy unless I hear from somebody here saying that it'll work and a part number. This new one that I installed and have since removed (sitting here in front of me) was run for probably 15 minutes and the center section of the "bamboo" is scorched black...the black has got on the windings and I'm nervous about a $5 part burning down my car. Therefore, I rely on the wisdom found here to put my mind at ease or tell me to keep a fire extinguisher handy~
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Old 08-25-2015, 08:01 PM   #11
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Default Re: Another coil resistor question

Capt. Kirk
If you have a Napa store they have Echlin ICR10 listed for all 37 to 40 trucks.
Echlin ICR40 listed for 41 6cyl and 8cyl trucks
Maybe find some NOS boxes.
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Old 08-26-2015, 05:19 PM   #12
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Default Re: Another coil resistor question

Got my coil back from Skip today. A little over a week from the time I dropped it in the mail. That in itself is impressive and what's more impressive is the quality of the work. I don't know what a new one looked like 80 years ago but I have no doubt that what I got back in the mail today looks as good or better than new! I can't wait to put it on this weekend and take the car for a drive.
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Old 08-26-2015, 06:06 PM   #13
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Default Re: Another coil resistor question

Couldn't wait to put the coil back on. Purrs like a kitten. Shut it off and wanted to see how it would restart. Less than one revolution and she was purring again. With the old resistor still in the car I was reading about 2.7 volts. I'll put the "new" resistor back in once I pull the car out of the trailer and check the voltage. If it's not right, I'll order one from Napa.
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Old 08-26-2015, 09:59 PM   #14
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Default Re: Another coil resistor question

You need to check your volt meter, It's very doubtful the engine will start with
2.7 volts. G.M.
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Old 08-30-2015, 04:15 PM   #15
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Default Re: Another coil resistor question

Had a good enough day today to pull the car out and check things. With the recently replaced ballast resistor, cold it read 6.2 volts on one side and 3.2 on the other. I drove it around for a few miles...the stench and smoke were aweful and I stopped several times to check under the dash to make sure there were no flames. When I got home and everything heated up, the voltage read 2.7 volts. That bamboo (or whatever it is) that supports the wire wrap is scorched black. I trust what you guys say but this can't be right. Ford didn't have all their new cars wheeling off the showroom billowing smoke inside the cab like a steam engine. I found a NAPA nearby that will have a replacement (with smoke free porcelain rod and .35 ohm) resistor waiting for me tomorrow. The car ran great with my new Skips rebuilt coil...didn't miss a beat and fires up in less than one revolution.
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Old 08-31-2015, 06:46 PM   #16
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Default Re: Another coil resistor question

OK, spent an hour on the car after work and I have some answers...I think. I picked up that ballast resister from Napa today (said .35 ohm). I installed it and it fired right up. So I thought I'd do some measuring of voltages and resistances. I have a digital multi-meter that I thought was good. I wanted to test the resistance of the coil and verify the resistance of the resistor. Of course, I checked the meter by holding the two leads together and...uggg...it read .5 ohm and there was no way to zero it. I checked a fresh skips coil and it read 1.1 ohm. So, do I subtract .5 from that (probably not) or just accept the reading. I checked voltages on each side of the resistor. 6.29 on the Bat side and 2.58 on the dist side of a hot resistor. A couple minutes later I checked the voltage again and it was 2.8 volts and it fired right up. I lost faith in that digital so I ran and bought a new analog meter. A recheck got me some better numbers (I think?). I put the old resistor back on and checked voltages. It read 3.2 volts with a warm to the touch resistor, it went to 3 volts with a hot resistor and, with the engine running it was at 4.5 volts at idle. I wasn't able to check running voltages with the digital because it jumped around too much. Are these numbers about right?
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