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Subject: broke 860

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Bob Thomas    Posted 11-08-2018 at 16:42:45 [URL] [DELETE]        [Reply] [Email]  
  • broke 860
  • The tractor was running fine , then nothing. No fire. The points and distributor cap are as new. One mechanic give a look and said replace the coil and you are good to go. Did not work. Later the same mechanic after a second examination found a burnt resister. Replace this and you are good to go. Again nothing, no fire. This mechanic would stop by on his way to work and tell me what he thought I needed. Can not get him back. Can not find another mechanic that will work on my tractor. Any ideas will be appreciated. 5810

    Tim Daley(MI)    Posted 11-09-2018 at 05:45:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: broke 860
  • HiYa Bob-
    Realize that just because a guy says he is a seasoned ‘mechanic’ does not mean he knows and understands these old FORD Electrical systems. ALL FORD vehicles used the 6V/POS GRN system, not just tractors. Later 50’s began using 12V with diesels and then guys started putting 12V batteries in their tractors. Swapping out batteries does not constitute a 12V switch over job. There are other factors as well, mainly, the generator and voltage regulator get removed from the circuit and a 12V alternator is then used. There is no resistor in the OEM 600/800 system. You can take your battery and alternator to a qualified starter shop who knows these old Ford systems and get them tested first. Also, it is a fact that 99.98% of all non-starting/non-running issues with these old Fords is due to the wiring being incorrect, and the majority of those are from a mucked up 12V ‘conversion’ being done by someone with no clue on what they are doing. There are but handful of correct ways to switch over from 6V to 12V and a hundred ways to switch it wrong. Here is a diagram of the OEM 6V system as a guide. Get an I&T F-020 Manual and use as a guide as well. Thee are plenty of qualified guys out there -just look harder. I suggest you go around to the starter/alternator shops and find one who is knowledgeable on old Fords.

    FORD 600/800 6V ELECTRICAL DIAGRAM:

    K.LaRue-VA    Posted 11-08-2018 at 19:36:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: broke 860
  • How did you determine "No fire"? An engine may be making good sparks and still not fire if the fuel system is empty or clogged. Where was the resistor that was burnt? There should not be a resistor unless this is a 12 volt conversion. Did you buy a coil that requires an external resistor? The burned resistor may have been the problem but now it is matched up with the wrong coil. It is easier and much cheaper to troubleshoot a problem before parts start being replaced. New parts just cost money and often add new problems. Finding electrical problems can be very frustrating. The first thing I'd do is put the old coil back on it with the new resistor. That is assuming you bought a resistor that is exactly the same type as the one that was burnt. Make sure the points are opening and closing by using a meter to watch the circuit open and close. Never assume anything is "as new" especially if it is new.

    bob Thomas    Posted 11-08-2018 at 20:15:18 [URL] [DELETE]        [Reply] [Email]  
  • Re: broke 860
  • Thank you for the reply. Firstly, I am a poor mechanic. Yes the tractor has been converted to twelve volts. The resistor is an exact replacement. The tractor was totally rewired about four years ago. The excellent mechanic who did it has passed away. Now I am scrapping to find someone to repair it. When I bought the coil I did not ask for one without the resistor. There is a very good possibility the coil has a built in resistor. I will try the old coil in the morning.

    Tim Daley(MI)    Posted 11-09-2018 at 05:50:28 [URL] [DELETE]        [Reply] [No Email]  
  • Re: broke 860
  • Is this the resistor you are seeing in your circuit?


    Tim Daley(MI)

    bob thomas    Posted 11-09-2018 at 09:12:18 [URL] [DELETE]        [Reply] [Email]  
  • Re: broke 860
  • That is the exact one. Can it be hooked up backwards?

    K.LaRue-VA    Posted 11-09-2018 at 15:45:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: broke 860
  • Nope. There is no frontwards or backwards to a resistor. Watch out with light bulbs though. Hook a light bulb up backwards and it becomes a light sucker.

    K.LaRue-VA    Posted 11-08-2018 at 21:04:04 [URL] [DELETE]        [Reply] [No Email]  
  • Re: broke 860
  • The 12 volt round can coils will usually have printed right on the side, something like "NO EXTERNAL RESISTOR REQUIRED" or "USE WITH EXTERNAL RESISTOR". The only reason I can think of that anyone would use an external resistor would be so they can wire a bypass to get hotter sparks when cranking the engine. I don't think it's worth the added wiring and parts to fail. I might feel different if I had to deal with winter temps a lot colder than it gets in Virginia..

    Bob Thomas    Posted 11-09-2018 at 09:25:13 [URL] [DELETE]        [Reply] [Email]  
  • Re: broke 860
  • Had an opportunity to check the new coil. It plainly states 'use with external resistor'. Guess I need to look elsewhere.

    K.LaRue-VA    Posted 11-09-2018 at 15:49:32 [URL] [DELETE]        [Reply] [No Email]  
  • Re: broke 860
  • A coil that says "USE WITH EXTERNAL RESISTOR" does go with the ceramic ballast resistor pictured above. They do make those ballast resistors with several different ratings. Some high performance engines used lower resistance to get hotter spark at high RPM. These tractors are low RPM engines, so a resistor rated around 1.5 ohms should work fine with a coil that says "USE WITH EXTERNAL RESISTOR".

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