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WD 12 volt conversion problem

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Dave C

07-13-2003 06:58:03




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My friend's WD was converted to 12 volt with single wire alternator a year ago. Ran fine until recently. Now keeps frying points (lasts maybe 2 hours). Have installed a 12 volt coil with a resistor between coil and distributor. New points and 12 volt condenser too. I have a feeling we've got something wrong with our coil setup. Anybody help???




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Bill

07-15-2003 07:50:07




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 Re: WD 12 volt conversion problem in reply to Dave C, 07-13-2003 06:58:03  
There is a misconception about 12 volt coils. The old Mopar and GM coils are designed to run at about nine volts. Your ignition gets around 14 to 15 volts when running. Chrysler used a resister and GM used a resister wire to correct this. Use a "12 volt" coil with a resister between the power source and the coil with a direct wire to the coil from the start position on the ign. switch.



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Steve in N.J.

07-14-2003 19:39:20




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 Re: WD 12 volt conversion problem in reply to Dave C, 07-13-2003 06:58:03  
Dave, The best way to check an igniton system is with a volt/ohm meter between the plus (+) and minus (-) terminals on the coil. What you want to achieve here is have approx. 2.7-3.3 ohms of resistance which includes the resistor your using in order for the ignition system to operate correctly. Most 12V coils measure around 1.5-1.7 ohms. So in order to get that 2.7-3.3 rating, you would need a resistor rated at about 1.8 ohms. This will put you into the resistance "ball park" so the points don't smoke on ya. We carry 3.0 12V coils in stock for our 12V conversions. This eliminates the need for an external resistor which takes a beating from Mother Nature, and eventually fails due to moisture and corrosion. A coil w/built-in resistor is less connections, cleaner, and more reliable. One of the fellows mentioned overcharging. That's possible, but I would think the overcharging would smoke the resistor first before the points. Also, this may sound dumb, but I've seen it many times. Make sure the wiring on the coil is correct. On 12V conversions, the plus (+) side of the distributor goes to the key, and the negative side (-) goes to the distributor. The 6V system is wired opposite. They will run backwards. Not well, but they'll run..... HTH Good Luck! If you need any more help, drop us a line, be glad to help ya out!
Steve/B&B Custom Circuits

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Doug in OR

07-14-2003 04:58:08




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 Re: WD 12 volt conversion problem in reply to Dave C, 07-13-2003 06:58:03  
When he converted to 12 volts, did he install the resistor in the ignition line, between the ignition switch and the coil? If not, this would possibly cause the coil to overheat, eventually shorting and causing this point problem. If there is no ignition resistor installed, I would expect that the coil is now bad. Best to just replace it with a 12 volt coil.



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Doug - Opsssss!!!!!

07-14-2003 17:54:52




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 Re: Re: WD 12 volt conversion problem in reply to Doug in OR, 07-14-2003 04:58:08  
You do not use a resistor when you already have a 12 volt coil. The resistor is only designed to drop the 12 volts down, when using a 6 volt coil. Ensure that the '+' terminal of the coil goes to the ignition switch. Leave out any resistors. Arcing between points when you are using a good coil can mean only one thing - a bad capacitor. New condensors are not always without defect.



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Brian G. NY

07-14-2003 18:00:50




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 Re: Re: Re: WD 12 volt conversion problem in reply to Doug - Opsssss!!!!!, 07-14-2003 17:54:52  
In my experience, all 12 volt systems use a resistor. The coil is fed 12 volts during cranking, but the voltage is reduced to somewhere between 6 and 8 volts during running to prevent burning of the points.



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Doug in OR

07-14-2003 19:30:16




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 Re: Re: Re: Re: WD 12 volt conversion problem in reply to Brian G. NY, 07-14-2003 18:00:50  
I believe Chrysler use to do it that way. Simply put, a 6 volt coil has a resistance of about 1.5 ohms. When you use 12 volts on a 6 volt coil, you install a 1.7 ohm resistor in series with the coil. The old Chrysler resistors work great as a dropping resistor for those in here who wish to convert to 12 volts and use your old coil.

If you measure the resistance of a 12 volt coil, you will find it somewhere in the range of 3.2 ohms. Generally, they build the resistor right into the coil.

Why he is losing his points is beyond me. It could be a bad condensor. It could be that the condensor is not getting a good ground connection. It could be that he is using a high-performance coil. Personally, I'd switch to an electronic ignition pick-up device, but only after finding the initial cause of the problem.

OBTW, the condensor has to somewhat match the coil. A mismatch could be another reason for failure.

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Carl (Ohio)

07-13-2003 11:04:46




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 Re: WD 12 volt conversion problem in reply to Dave C, 07-13-2003 06:58:03  
Dave You might try moving the resistor to the other side of the coil (between the switch and the coil) instead of between the coil and dist to see if that cuts down on the burning also check the voltage with the tractor running as the voltage regulator may be bad (running voltage shouldnt be over 14 1/2 volts at the alt) Good Luck Carl



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