Ignition condenser chat and cheap backup product.

[Zukjeff]

I spun up the original dizzy on the 1984 12v coil (that was in the truck ) today to see if it worked.

I have done enough electronics and RF to know the coil and condenser are part of a tuned circuit. They need to be 'matched' like the prongs of a tuning fork. The condenser is not there to quench sparks from the points contacts like some say.

 

 The condenser in my dizzy is very old and likely to be intended for use with an original  pre 60s 6v coil, not a more modern 1980s  coil.

 

12v battery setup with the 12v coil in the dizzy and spun by hand or by battery drill gave a weak spark.

 

The original condenser tested ok on the workbench as a 0.6 micro-farrad  capacitor but had some resistive leakage of about 800k ohms. 

 

None of the 5 auto shops in my city of 120,000 people had any cross reference for any condenser for any of the flathead motors i quoted. Nor did they have any idea of what a condenser was let alone know what stock they had ! 

The helpful person at the counter at Beeps auto let me look through their trays of points and condensers.

A Bosch GB538 intended for early GM cars looked the most generic. 

Ripper $7.00

 

It tested at a 0.25 MFD capacitor with no resistive leakage. 

 

I was correct in thinking that the impedance of the old 1940s coils and condensers is different to those of the 70s onwards.

 

The new condenser setup on my test bench gave a much stronger 'crack' of a spark.

 

A few quick mods had the screw terminal of the new points recrimped to its shortened lead.

Flattened the mounting tab a bit, cut half of it off, marked and drilled two of 3.5mm holes. Clean up with a small rat tail file.

Mounted securely in the dizzy on the upwards facng dimple so it cannot rotate.

 

Until I machine down the guts of a 80s reluctor dizzy this will do.

 

 

 

 

 

 

[kencombs]

If my memory is still good (sorta questionable), all the condenser specs in my old tuneup manuals are really close to 30-35mfd.  All makes but I don't recall any specs for 6v systems.  

 

I've subbed generic GM condensers for Mopar/Ford and several small engines and tractors over the years.   Because finding the 'right' one can be a challenge.

[Robert Harrison]

Fine work Jeff.  Standard Products has been making ignition parts before we shipped cars to Oz.  My father in-laws 1960 dodge pickup with flat head may have been 12V if so standard products may have had a "correct" condenser that might have worked.  I think by 1960 they may have gone to 12V.  

[Zukjeff]

The voltage of the coil does not affect the resonate frequency of the coil capacitor combo.  It's just if old coils had a different impedance they would require a different value condenser. 

 

 

[Dodgeb4ya]

On 5/31/2025 at 3:38 AM, Zukjeff said:

I spun up the original dizzy on the 1984 12v coil (that was in the truck ) today to see if it worked.

I have done enough electronics and RF to know the coil and condenser are part of a tuned circuit. They need to be 'matched' like the prongs of a tuning fork. The condenser is not there to quench sparks from the points contacts like some say.

 

 The condenser in my dizzy is very old and likely to be intended for use with an original  pre 60s 6v coil, not a more modern 1980s  coil.

 

12v battery setup with the 12v coil in the dizzy and spun by hand or by battery drill gave a weak spark.

 

The original condenser tested ok on the workbench as a 0.6 micro-farrad  capacitor but had some resistive leakage of about 800k ohms. 

 

None of the 5 auto shops in my city of 120,000 people had any cross reference for any condenser for any of the flathead motors i quoted. Nor did they have any idea of what a condenser was let alone know what stock they had ! 

The helpful person at the counter at Beeps auto let me look through their trays of points and condensers.

A Bosch GB538 intended for early GM cars looked the most generic. 

Ripper $7.00

 

It tested at a 0.25 MFD capacitor with no resistive leakage. 

 

I was correct in thinking that the impedance of the old 1940s coils and condensers is different to those of the 70s onwards.

 

The new condenser setup on my test bench gave a much stronger 'crack' of a spark.

 

A few quick mods had the screw terminal of the new points recrimped to its shortened lead.

Flattened the mounting tab a bit, cut half of it off, marked and drilled two of 3.5mm holes. Clean up with a small rat tail file.

Mounted securely in the dizzy on the upwards facng dimple so it cannot rotate.

 

Until I machine down the guts of a 80s reluctor dizzy this will do.

 

 

 

 

 

 

Informative and nice clean work!👍

[keithb7]

I have limited understanding of electrical engineering. What I know what I read in mechanical repair books and internet reading. 
 

I am under the impression that the capacitor (ignition condenser) assists in suppressing arcing when points open & close. Storing voltage when the points open. Also maybe it helps recharging the coil quickly when the points open?  Too much or too little capacitance can result in a build-up on one point contact, and a void on the opposing point contact. 
 

Am I on the right track? Without going into algebra to prove, what else is the primary job of the condenser? 
 

Thx. 

Edited June 1 by keithb7