Tweet
Can anybody tell me what the voltage should be at the + side of the coil on a 66 350hp with points ignition? I am getting 12+ into the ballast resistor and about 5.6 volts at the coil . Seems like it should be more like 8 volts.
-
-
Re: Voltage At Coil
I think the conventional wisdom is about 8 volts. As has been previously discussed here, the resistance of the BR will increase with temp so that voltage will remain somewhat constant at higher RPM. Is the input voltage 12 or is it closer to 13.7? That's about the voltage I would expect with the engine running and everything in proper order in the Alt/regulator/battery. If your input voltage is as low as 12 that could account for the lower voltage to the coil. The resistance of the BR (Delco) should be about 1.4 ohms at room temp. Some aftermarket resistors run as much as 1.7, which would also lower the voltage at the coil. -
Re: Voltage At Coil
I think the conventional wisdom is about 8 volts. As has been previously discussed here, the resistance of the BR will increase with temp so that voltage will remain somewhat constant at higher RPM. Is the input voltage 12 or is it closer to 13.7? That's about the voltage I would expect with the engine running and everything in proper order in the Alt/regulator/battery. If your input voltage is as low as 12 that could account for the lower voltage to the coil. The resistance of the BR (Delco) should be about 1.4 ohms at room temp. Some aftermarket resistors run as much as 1.7, which would also lower the voltage at the coil.Comment
-
Re: Voltage At Coil
I am assuming this is with the engine running. When my dwell is set correctly, I read about 11 volts on the plus side.
RonComment
-
Re: Voltage At Coil
I am assuming this is with the engine running. When my dwell is set correctly, I read about 11 volts on the plus side.
RonComment
-
Re: Voltage At Coil
There was an extensive discussion regarding the difficulty of making this measurement correctly in the last few months. Try a search of the archives under distributor voltage or Ballast resistor. It will save you a lot of heartache.Comment
-
Re: Voltage At Coil
There was an extensive discussion regarding the difficulty of making this measurement correctly in the last few months. Try a search of the archives under distributor voltage or Ballast resistor. It will save you a lot of heartache.Comment
-
Re: Voltage At Coil
The actual voltage you measure is a function of which ballast resistor you have, and among the "normal" 1.7 ohm ballasts there is some variation in replacement parts, depending on the manufacturers.
Also, the voltage measurement will depend on whether the engine is running or not. If the points are closed and the engine is not running you will be measuring the DC voltage. If the engine is running the voltage will be less because the circuit opens and closes, so a typical analog voltmeter will be reading some sort of average.
DukeComment
-
Re: Voltage At Coil
The actual voltage you measure is a function of which ballast resistor you have, and among the "normal" 1.7 ohm ballasts there is some variation in replacement parts, depending on the manufacturers.
Also, the voltage measurement will depend on whether the engine is running or not. If the points are closed and the engine is not running you will be measuring the DC voltage. If the engine is running the voltage will be less because the circuit opens and closes, so a typical analog voltmeter will be reading some sort of average.
DukeComment
-
Re: Voltage At Coil
Thanks for the info guys. The voltage was measured with the engine off. I am chasing an ignition gremlin that is causing some very strange behavior in my car. I may have found the source, there are some carbon tracks that indicate arcing between the underside of the rotor and the distributor post. I'll be installing a new cap and rotor and rechecking to see what the running voltage is.Comment
-
Re: Voltage At Coil
Thanks for the info guys. The voltage was measured with the engine off. I am chasing an ignition gremlin that is causing some very strange behavior in my car. I may have found the source, there are some carbon tracks that indicate arcing between the underside of the rotor and the distributor post. I'll be installing a new cap and rotor and rechecking to see what the running voltage is.Comment
-
Re: Voltage At Coil
Thanks Bill. I looked through the last two or three archive files and couldnt find them. Can you give me any more clues?Comment
-
Re: Voltage At Coil
Thanks Bill. I looked through the last two or three archive files and couldnt find them. Can you give me any more clues?Comment
-
Re: Voltage At Coil
When you think in terms of voltage, you're shooting yourself in the foot!
Dale.Comment
-
Re: Voltage At Coil
When you think in terms of voltage, you're shooting yourself in the foot!
Dale.Comment
Comment