Ignition coil with additional capacitor attached, help (850)

reptar · Post by **reptar** » 06 Jul 2012, 17:49

Hi enthusiasts,

I've replaced an ingnition coil to try and locate a potential ingnition problem when engine bay warms up. I had a 35volt220uF capacitor connected across the positive (red wire) low tension terminal of the coil - to earth. I understand this will boost the high tension coil output pulse. Coil pt no. 0221601005. The capacitor was not connected to two other coils of the same part no. I sourced from the wreckers. My thinking is that has this extra secondary coil power caused a breakdown of the insulation between the primary and secondary coils.

My question: is this capacitor standard for this coil on a 850 b5252s engine or has the previous owner (may be) had it fitted to boost power?

Post by **jreed** » 07 Jul 2012, 06:21

I have a different model year ('97) and engine (B5254T), but my coil does not have an extra capacitor. On eBay I found an image of a used coil (attached) that also doesn't show a capacitor. My guess is that the capacitor on your coil is not original.

: Bosch 0221601005 ignition coil for Volvo 850; Bosch 0221601005 ignition coil for Volvo 850.png (197.46 KiB) Viewed 1873 times

Bigblue · Post by **Bigblue** » 07 Jul 2012, 08:33

My guess is that the cap was added to remove radio noise...That's an old school, pre-electronic ignition, breaker point system fix...I cannot imagine it intensifying spark, I would think it would have the opposite effect due to creating a delay in coil saturation while the cap charges up...I do not think it would cause a primary/secondary insulation breakdown, but that, too, is just a guess...For filtering out radio noise it is better to put the cap right on the radio between the power lead and the radio chassis...

Are you the original owner?...

reptar · Post by **reptar** » 07 Jul 2012, 09:37

Here is an image of my ignition coil.

I bought the car with this in it. Any thoughts?

kiss4afrog · Post by **kiss4afrog** » 12 Jan 2013, 07:25

I have two of those coil module assemblies and neither has that cap. I'd disconnect it and see how it drives and if you notice any noise in the radio. If it doesn't drive any different I'd leave it disconnected as no post here seems to identify it's purpose and it's not stock.
If you notice radio noise it's best to use a purpose dedicated cap in the radios power feed line but if there is radio noise it's likely from a bad alternator, one that's creating noise in the system as the ignition shouldn't be able to. It could still be charging the battery properly.