Originally Posted by Perry 951

Let's bring this conversation back to reality.

We're talking about a very common Bosch coil here; not a massively rare or expensive unit. The current production number is 0221118322 and costs about $80. For most shops, you're gonna pay an hour of diagnostic time for them to hook up a scope and check dwell and rise. Unless they are below $80 a hour, it's worthless to do so and a better value just to replace it. I also checked the Bosch site as well as my factory 951 manuals, Alldata, Identifix, and Motor and none of them list anything beyond primary and secondary resistance.

Without the charge time data, testing with a scope is about as accurate as viewing and listening to the spark. Comparing to another coil that you do not have specifications for is comparing nothing to nothing. Maybe you can contribute more to the community by supplying the information?

I've checked, looked at, and listened to hundreds of coils over the last 13 years of working on cars for a living, and probably even more in my 35 years of working on cars. You can tell a weak coil from a good one by the color, brightness, and sound of the spark.

Originally Posted by Tom M'Guinn

Agreed. Not sure I've seen as many sparks as you, but I've definitely seen weak sparks just by looking at them. One turned out to be bad wiring even though the coil itself was fine. Not sure I could tell a borderline spark by just looking at it, or have any idea what happens to it under pressure, but I've seen them where something was clearly wrong. So even for a weekend mechanic, I think it's worthwhile to take a peek. I think tradesmen/pros learn to be much more efficient about repairs than us weekenders. It's easy to get enamored with technology and testing and learning when it's all for fun. But when you are making a living doing something, you won't last long charging $200 to test an $80 part.

Originally Posted by m42racer

I'm sure that is correct.

So to, is when that $80.00 part you just sold didn't fix the problem. What do you tell the customer then? " I looked at the spark and it didn't snap really loud, so I sold you a new coil".

I get the cost different point. But regardless of cost, there is a correct way to test something and a "shade tree" way. You won't be in business long when you run out of shade tree mechanic fixes either.

You cannot expect a good pro shop to drop their service costs just because you own a 944. You should expect a pro shop to do their due diligence and check the complete electrical system to make sure the coil is the problem and not the other parts of the ignition system. I can here it now, "why did you sell me a new coil and not check the rest of the system".

Or, "why are you charging me $$$$$ to test the complete system when you found it was just the coil @ $ 80.00?" The answer would be simple. Because that is the correct way to test the system and that is what you agreed for us to do.

You get what you pay for and you make your mind up what you are prepared to pay for.