12 Volt Coil Resistance Readings

[19Fordy]

Should the primary and secondary coil resistance readings be the same both when the engine is cold and right after you shut engine off?
Coil is 12 volts used on a 6 to 12V conversion on an 8BA.

The problem I am trying to solve is that after running about 15 min at idle and on the road the engine shuts shuts off - as if someone flipped and OFF switch.
15 seconds later it will start right up and the process is repeated.

I am using a Mallory Unilite distributor with a new electronic module and ballast resister. Mallory set up has been working fine for last 10 years and all of a sudden this started. Car has electric fuel pump that is pumping.

Got me puzzled. Thanks.

 

[flatjack9]

What is the primary resistance on the coil and what is the resistance on the ballast resistor? Is the resistor still working?

 

[cmbrucew]

Circuit breaker may be weak.
Bruce

 

[JSeery]

Circuit breaker may be weak.
Bruce

What would the circuit breaker have to do with anything? Are you referring to the original Ford CBs? The only things connected to the circuit breaker is the lighting circuits.

 

[BUBBAS IGNITION]

Should the primary and secondary coil resistance readings be the same both when the engine is cold and right after you shut engine off?
Coil is 12 volts used on a 6 to 12V conversion on an 8BA.

The problem I am trying to solve is that after running about 15 min at idle and on the road the engine shuts shuts off - as if someone flipped and OFF switch.
15 seconds later it will start right up and the process is repeated.

I am using a Mallory Unilite distributor with a new electronic module and ballast resister. Mallory set up has been working fine for last 10 years and all of a sudden this started. Car has electric fuel pump that is pumping.

Got me puzzled. Thanks.

Be glad to help. What is the resistance primary and secondary???? What exact coil is it ???. The Mallory will shut off in a heart beat if the amps exceeds 8 amps......

 

[19Fordy]

Bubba: Here's the info:
Mallory coil # 29216 with readings of .7 ohms Primary resistance and 8.98K ohms Secondary resistance.
Distributor is Mallory YL-2527501 converted to electronic ignition 10 years ago. It uses:
Mallory ignition module 6100M,
Rotor #335,
Mallory circuit surge protector 29371
Distributor cap 209
Mallory external ballast resistor 700M.
Everything worked fine for 10 years until last week.
Question: Where do I place my digital multimeter leads to check if I am exceeding 8 amps? Thank you all for your help. Looking forward to your reply as I am not an electrical 'whiz" and don't want to just undoing my wiring harness not knowing what I am searching for. JIM

 

[BUBBAS IGNITION]

I dont have the info here in front of me but heres what i feel is your problem. This has been an issue in the past. Mallory made a couple coils a 29216 and a 29219 . One was .7 ohm and the other was 1.5 etc ohm. Forget the resistor for a moment , if ya ran the .7 ohms with a 14 volt charging rate the module could see 20 amps . The module doesnt like 20 amps even with current limiting protection and would die a slow death....Adding a resistor of 1-1-5 ohms would help but not enough from time to time...
My suggestion would be to use a coil with 1.5 ohms and a 1.5 ohm resistor etc.

What part changed in the 10 years you have ran this system.....

 

[Drbrown]

Just curious ..... are you using a converted generator or an alternator ? Have you checked its max voltage output ? Can you eliminate the ballast resister and change your coil to one with the required internal resistance ? My '47 was converted to a 12 volt system uses a 12 volt Blue Flame coil which has an internal resistor. Not cheap but they have a good reputation.

 

[BillM]

Question: Where do I place my digital multimeter leads to check if I am exceeding 8 amps? Thank you all for your help. Looking forward to your reply as I am not an electrical 'whiz" and don't want to just undoing my wiring harness not knowing what I am searching for. JIM

I would recommend not trying to measure your coil current directly with your multi-meter; if the current is higher than expected you could blow a fuse or otherwise damage the meter. It would be safer to measure the voltage drop across the ballast resistor while the module is conducting. Google "testing Mallory Unilite" for how to activate the module. Just don't leave the module conducting longer than needed to get a reading. Use Ohms law to calculate the current with the resistance of the ballast resistor and the voltage across it. I am wondering if your new module is seeing excess current and safety circuits in it are shutting it down, which would explain why it recovers in only 15 seconds.