Voltage at Coil
Thread Starter
Racer
Joined: Apr 2004
Posts: 292
Likes: 41
From: Falls Church VA
Voltage at Coil
Having a spark problem and troubleshooting... When I measure voltage at the coil with engine off, I get 11.9v at the coil (primary.) As I crank the engine, the coil voltage (primary) drops to 9.2v. Coil resistance is 1.6ohms. Problem? I am considering replacing with lower resistance coil. Appreciate any feedback.
Thanks.
Steve
Thanks.
Steve
Race Director
Joined: May 2006
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The positive terminal of the coil while cranking should receive full battery voltage. Which terminal are you taking those readings, positive or negative?
How are you measuring resistance, where are you placing the probes?
The 1969 manual shows primary coil resistance as 1.77 to 2.05.
The secondary resistance is 3,000 to 20,000.
How are you measuring resistance, where are you placing the probes?
The 1969 manual shows primary coil resistance as 1.77 to 2.05.
The secondary resistance is 3,000 to 20,000.
Last edited by MelWff; Jun 30, 2020 at 06:15 PM.
Is my vette stock?? HAHA
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If you are saying input voltage changes then your voltage supply wire is incorrect. So if you are running an aftermarket HEI and using the original coil wires you need to switch to a different wire. It’s been stated in some instructions to use the yellow wiper wire.
Thread Starter
Racer
Joined: Apr 2004
Posts: 292
Likes: 41
From: Falls Church VA
Voltage at/on battery is 12.2v.. Voltage at the coil (voltmeter with one lead on the coil's positive terminal and one lead on the coil's negative terminal) with key turned to accessory I get 11.9v. When cranking it drops to 9.2v.
Last edited by Silver72; Jul 1, 2020 at 07:16 PM.
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From: Va.Beach Va.
Tech Contributor
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Gordon is asking some good questions. Your coil voltage measurements don't mean much if we don't know what the battery voltage is during cranking.
Le Mans Master
Joined: Sep 2013
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From: near the thumb in the mitten
IDK anything about your point conversion kit. The coil should have battery voltage when engine is cranking. So if battery voltage is 11.5v cranking coil should be 11.5v or very close. Wire runs from R terminal of solenoid to coil, that carries battery voltage to coil, when solenoid is turned on by the S terminal. Once engine starts and starter disengaged voltage at coil drops to 9.2v to increase points life. You made need to review conversion. Instructions.
Le Mans Master
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Since a coil discharges 300 times a second at 4500 RPM, it can charge up quicker than your meter will ever read.
Is my vette stock?? HAHA
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That’s the reason I asked if it’s HEI, it needs 12 volts all the time where a regular coil does not
Burning Brakes
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Race Director
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From: South Western Ontario
That ignition simply connects to the ballast resistor, so the resistor will still be present. During running, the coil voltage should be less than the battery voltage. But as I posted before, check the wire from the solenoid to the positive terminal of the coil. It will provide battery voltage during cranking.
Team Owner
Joined: Jan 2006
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From: Crossville TN
Some electronic ignition conversions may not work properly if you feed power to it thru that resistance wire. Remove that resistance wire from the coil and run a 12vdc jumper wire to it to see if it works as expected.
Instructor
Joined: Oct 2014
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From: San Jose CA
Hi Glenn,
Be careful of a red herring. We don't know if 220 degrees is too hot. You said that the Sniper went dark, this is more alarming to me than a hot coil. How is the Sniper configured, controlled timing or non-controlled timing? My assumption is you are operating in non-controlled timing mode, if so the only involvement from the Sniper with the ignition is an input to sense the RPM. Run the car until is cuts out, then check for spark to confirm that you indeed have an ignition problem.
Be careful of a red herring. We don't know if 220 degrees is too hot. You said that the Sniper went dark, this is more alarming to me than a hot coil. How is the Sniper configured, controlled timing or non-controlled timing? My assumption is you are operating in non-controlled timing mode, if so the only involvement from the Sniper with the ignition is an input to sense the RPM. Run the car until is cuts out, then check for spark to confirm that you indeed have an ignition problem.