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Ignition Coil Condenser Function 30.0 EK-15R/9238C

dapoags

Registered
I'm reaching out to the group to see if anyone can clarify the function of the the 2 condensers in my ignition system connected to the coil and alternator respectively (Onan P/N 312-0058) .

I replaced the coil and the other ignition parts including the internal distributor condenser, after our prime power generator shut down over the weekend. Napa couldn't find replacement condensers for the coil and alternator. They appear to be Onan add on parts as they are listed in the manual.



30.0EK-15R/9238C
SN: 0670205039

Ford-Model C5PF -6005-A SO31

Serial is 39982 A-1-HM
CID 240

!. Can anyone explain the function of the condenser mounted on and connected to the positive terminal of the coil?

2. Also the one mounted on and connected to the alternator?

3. Does anyone know the difference between a condenser and a resistor as applied to a 1970 Ford the ignition system

The existing condenser attached to the coil is hanging on by a thread and needs to be replaced ASAP. One of our employees went back to Napa, they gave him a "resister" in place of the "condenser". I'm concerned that putting in the wrong part could damage the ignition system.

respectfully,
DAP
 

Wayne 440

Registered
I'm not going to guess why Onan put condensers (AKA capacitors) in those locations. But I will say that a resistor is not an appropriate substitute for either part in this case.

Take that resistor back to NAPA and tell them to stick with looking up parts, not re-engineering generator sets.
 

len k

Subscriber
Last Subscription Date
12/12/2018
Condenser is another name for a capacitor (cap).

I'm not familiar with a 30EK but :

Typically cap on + side of a coil is just for noise suppression ( EMI, RFI, electrical noise ....).
Same for caps on + output of alternator.

On engines and cars these are tootsie roll sized caps ~ 1.5 inch long, they are low capacitance "by-pass" caps , ~ 3-5 mfd. Just called by-pass since located where they are near RF noise sources, they allow RF voltage (noise) to go straight to ground, "by-passing" the long wires to bat , that would act as an antenna.... radiating a lot of RF noise into the environment.

Basically RF noise is AC voltage oscillation in the RF frequency region. Can be caused square edges of a current draw for example.

Basically the RF voltages "by-pass" they long wires to bat, and take the short cut thru the cap to ground. That's why when used in this way they are called by-pass caps...... it's just how they are used , rather than something really special about the cap.

Don;t know what resistor you have..... but for RFI (EMI) noise suppression spark wires can have a resistor at end of wire, or a distributed resistance ( carbon in as the conductive "wire") ... this acts to make it a crummy antenna for radiating electrical noise in to the environment. Something about impedance mismatch between wire and air ( IIRC air has an effective AC impedance of ~ 470 ohms)
 

dapoags

Registered
I'm not going to guess why Onan put condensers (AKA capacitors) in those locations. But I will say that a resistor is not an appropriate substitute for either part in this case.

Take that resistor back to NAPA and tell them to stick with looking up parts, not re-engineering generator sets.
You know your in trouble when every employee at the local hardware store draws a blank stare when you ask if they have a miter box
 

dapoags

Registered
Condenser is another name for a capacitor (cap).

I'm not familiar with a 30EK but :

Typically cap on + side of a coil is just for noise suppression ( EMI, RFI, electrical noise ....).
Same for caps on + output of alternator.

On engines and cars these are tootsie roll sized caps ~ 1.5 inch long, they are low capacitance "by-pass" caps , ~ 3-5 mfd. Just called by-pass since located where they are near RF noise sources, they allow RF voltage (noise) to go straight to ground, "by-passing" the long wires to bat , that would act as an antenna.... radiating a lot of RF noise into the environment.

Basically RF noise is AC voltage oscillation in the RF frequency region. Can be caused square edges of a current draw for example.

Basically the RF voltages "by-pass" they long wires to bat, and take the short cut thru the cap to ground. That's why when used in this way they are called by-pass caps...... it's just how they are used , rather than something really special about the cap.

Don;t know what resistor you have..... but for RFI (EMI) noise suppression spark wires can have a resistor at end of wire, or a distributed resistance ( carbon in as the conductive "wire") ... this acts to make it a crummy antenna for radiating electrical noise in to the environment. Something about impedance mismatch between wire and air ( IIRC air has an effective AC impedance of ~ 470 ohms)
In its previous life this generator may have been back up at a civil deference warning system sub-station
 

dapoags

Registered
Thanks everyone, I think I've got it.

This genset may have been backup power at one of our civil defense sub-stations, the spec "C" has the parts in its manual, that might make sense.
 

len k

Subscriber
Last Subscription Date
12/12/2018
Bottom line is caps on + side of coil and alternator are not needed for engine to run....... but should be connected to keep radio airwaves clean of EMI noise...... remember 1960's cars that went click click click on AM radio band..... that was ignition noise, and it goes to all the other radio/TV bands also. FM radio by it's technical nature is more immune to this noise than AM radio. Not sure how immune digital TV is.

If you have points then want a cap to neg side of spark coil. Protects points and allows good spark quality.

If instead of points you have an electronic pickup modual read the manual. Onan 6.5NHE types have electronic ignition and if have a cap on neg side of spark coil then spark stops ( according to a Staker with that problem , cap somehow fools the modual.

.
 
Last edited:

Motorhead

Subscriber
Age
67
Last Subscription Date
07/09/2019
Best thing you could do is get rid of the points distributor and install a Ford pointless distributor with their electronic ignition module. Get a much hotter spark and they are real dependable. We had them on the 300 ci Fords when I was at UPS and the mechanics even retro fitted the older package cars with points to the later electronic ignition and module. They also made the engine pretty waterproof when we drove in the rain and through puddles and some water crossings.
 

Motorhead

Subscriber
Age
67
Last Subscription Date
07/09/2019
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