Onan 312-0256 Condenser

[Bill D 1,623]

Is there a substitute for the Onan 312-0256 Condenser used on the P216.  It's out of stock on Onan Parts.com and Cummins.  Is there anything special about it or can I use one from a Kohler if needed. Thanks.

Edited April 25 by Bill D

[lynnmor 6,819]

7 hours ago, Bill D said:

Is there a substitute for the Onan 312-0256 Condenser used on the P216.  It's out of stock on Onan Parts.cim and Cummins.  Is there anything special about it or can I use one from a Kohler if needed. Thanks.

 

I searched the part number and found several sites that have them.  The only thing special is the longer lead.  Here is a photo that shows the specifications:

 

[Bill D 1,623]

On 4/25/2024 at 3:43 AM, lynnmor said:

 

I searched the part number and found several sites that have them.  The only thing special is the longer lead.  Here is a photo that shows the specifications:

 

Thanks for the info. I have seen some places that appear to have them in stock and some aftermarket. Does anyone know if the polarity is different because the condenser connects to the positive terminal?  

[lynnmor 6,819]

My opinion is that the condenser is there for the purpose of reducing interference on radios.  Some say that it clips the high voltage spikes to protect the ignition module while others believe it works like a points system to provide a hotter spark.  I do know that some have even run pulling tractors with no condenser at all.  If one is shorted you can disconnect it to see if the spark returns.  The same condenser was used by General Motors cars in the 50's and 60's, for radio noise but they are getting old and prices are crazy because of collectors wanting original parts.  When I did a quick search online at several popular electronics suppliers all I could find is the modern designs that would take some work to install.  Hopefully someone can point us in the right direction so we could buy these things at a sensible price.  I would think that the polarity would always be with the case grounded and the wire to positive, of course they may not be polarity sensitive at all.

[Bill D 1,623]

Thanks @lynnmor.  Any thoughts on this @Handy Don?

[953 nut 51,980]

On 4/26/2024 at 1:27 PM, lynnmor said:

Some say that it clips the high voltage spikes to protect the ignition module while others believe it works like a points system to provide a hotter spark.

The condenser is there to suppress the arc that occurs when the ignition points first open. Without the condenser your points won't last very long but the engine will run just fine for a short time.

The 0.3 microfarad condenser shown by @lynnmor would be 300 nanofarads which is in the proper range for a battery ignition system.

 

The Kohler 230722 Condenser fits all battery ignition single cylinder and twin cylinder from the K-90 to the K-582.  The 235786 condensers are for the magneto equipped Kohler engines only K-161 to K-301

The unit of measure for a condenser is the Farad. Many electronic components like radios and TVs use capacitors that are in the microfarad range (ten to the minus six power Farads) and our small engines use a condenser that is in the nanofarad range (ten to the minus ninth power Farads) which is based on the voltage range they work in. A magneto ignition system uses a 100 to 250 nF condenser and a battery ignition system uses a 200 to 500 nF condenser. A good multi-meter will have a capacitor testing function.

Armed with this information you can walk into your auto parts store and get a very confused look on the face of the person on the other side of the counter. The capacitance is not listed on the package and probably not in any of the on-line data they have for the condensers they stock. You just have to go by the application chart and be sure that the condenser you are buying is for the type ignition system your engine has, not just the horsepower or engine size.

If an engine idles well, but runs erratically when revved up, like it hits and misses, pops and backfires, then chances are, it needs a new condenser/capacitor. And always install a condenser/capacitor with the wire facing downward so rain water and/or when washing off engine, water will not enter inside condenser/capacitor, ruining it. With water inside the condenser, this will also allow it to idle well, but cause it to run erratically when revved up.

What is a farad (F)? A farad (F) is the standard unit of capacitance (C) in the International System of Units (SI). It indicates the ability of a substance to hold an electric charge. The value of most electrical capacitors is expressed in farads, microfarads (µF) or nanofarads (nF)

[lynnmor 6,819]

Since the Onan in question has no ignition points and uses a Hall effect module to do the switching there may not be a need for a condenser.  If I ever get a bad module again I will do an autopsy on it to see if there is an internal capacitor and see if the module can be duplicated since the price and availability is getting to be a real issue.  At times there are modules listed on the Bay that I suppose are imported.  I do have a meter to check capacitors so maybe I'll get a read on a couple that I have on the bench and then compare to available auto parts still available.

[953 nut 51,980]

44 minutes ago, lynnmor said:

has no ignition points

Regardless of what device opens the current flow through the primary winding of the ignition coil there will be instantaneous current induced from the secondary winding back to the primary windings and the condenser quenches that spike.

[lynnmor 6,819]

55 minutes ago, 953 nut said:

Regardless of what device opens the current flow through the primary winding of the ignition coil there will be instantaneous current induced from the secondary winding back to the primary windings and the condenser quenches that spike.

Understand that, but maybe there is a condenser within the module.