ballast resistor
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New User
Joined: Jul 2001
Posts: 14
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ballast resistor
From what I've read there should only be around 9 volts going to the distributor coil. Is this right? (1963 292, still using points)
I just replaced the coil, I checked the voltage on the + lead and am getting 12+ volts on ether side with key in run position and also with the engine running. I did install a ballast resistor (had the parts guy look up the right one for me, I think) and I get the same voltage readings with OR without it. I'm also geting the "exact" same voltage reading on ether side of the ballast resistor as well.
Any idea what value I should be using in a ballast resistor?
Mabe a particular part number I should ask for so I get the right one?
They were out of the resistor wire so unless I want to order resistor wire the ballast resistor is my option.
Many thanks in advance.
Ray (63Fever)
I just replaced the coil, I checked the voltage on the + lead and am getting 12+ volts on ether side with key in run position and also with the engine running. I did install a ballast resistor (had the parts guy look up the right one for me, I think) and I get the same voltage readings with OR without it. I'm also geting the "exact" same voltage reading on ether side of the ballast resistor as well.
Any idea what value I should be using in a ballast resistor?
Mabe a particular part number I should ask for so I get the right one?
They were out of the resistor wire so unless I want to order resistor wire the ballast resistor is my option.
Many thanks in advance.
Ray (63Fever)
Elder User
Joined: Aug 2001
Posts: 942
Likes: 0
From: South Texas
ballast resistor
The results you measured are correct with or without a ballast resistor in place. The coil circuit is a normally open circuit with +12V battery standing and is only closed thru to ground during point operation in conjunction with the condenser charging. If the engine is idiling at 500RPM, the points will open & close 2000 times per minute. Using a standard meter set on voltage, there is no way you will see the true voltage reading during the coil firing cycle. It is just too fast for the meter to pick up. Get an oscillascope if you want to see the true voltage. The only reason for the ballast resistor is to lower the voltage (and thereby lower the current flow) thru the points contacts. This will give longer life to the point surfaces by reducing the amount of arching, metal transfer and oxidation.
Hope this helps explain things.
Dialtone
Hope this helps explain things.
Dialtone
Postmaster
Joined: Nov 2000
Posts: 2,557
Likes: 2
From: Texas
ballast resistor
I guess that explains why I used to burn so many sets of point in my 71 cutlass a few years ago. I had to replace them darn things about every 1500 miles or so and they always were pitted and burnt.
Krosati
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Krosati
Visit my homepage at ClubFTE
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Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
ballast resistor
Dialtone is right. In order to measure the voltage on the coil, the points have to stay closed to complete the circuit. With the cap off, just bump the engine over until they are closed. With the key on you will see around 6 volts on the + side and should not see more than .25 volts on the - side. The resistor wire spec. is 1.3 to 1.4 ohms. With a stock coil primary of 1.4 to 1.54 ohms this creates the proper voltage drop across the divider between 6 and 6.5 volts. Something interesting is that the 12-volt ignition systems still used the 6-volt coils from the older systems. They pump 12 volts through them on start-up for a boost in power but revert to the 6 volts when running, pretty clever. Run them straight on 12 volts and they will overheat and burn out along with the points.
Barry
Barry
