Testing Ignition Coil - What’s the proper resistance?

[Andrew325is]

Bentley manual says 0.50 ohms for primary resistance and 5000 ohms for secondary resistance. I tested my coil and it’s 1.2 ohms primary and 5700 secondary. Bentley manual says to replace if higher than the listed values so I got a new Bosch coil. New coil tests 1.2 ohms primary and 6600 ohms secondary. Tested with 2 different Fluke multimeters. What does it mean? Are both bad or is the old one okay?

[digger]

Why are you texting coils on first place? When I tested mine years ago it didnt match with bentley either but there weren't any issues. I'd say it's fine

[Kershaw]

I bought 2 new ones and it was nowhere near spec in the Bentley. It's fine.

[Andrew325is]

Refreshing everything and the old plugs have carbon deposits so I thought I’d test the coil.

[Andrew325is]

I found your thread about this here: https://www.r3vlimited.com/board/sho...d.php?t=376659

So I guess the new coil is fine. To test the old one it looks like I'd need to use an oscilloscope.

I looked up how to test it in the factory E30 repair manual and it has a 3 step procedure:

1. "Multimeter Test: Measure resistance of primary coil - term. 1/15 = 0.5 ohm +-10% and secondary coil - term. 15/4 = 6k ohms +-10%."

2. "Inspect connection plate for hairline cracks and traces of burning. Check plug (S) for tight fit - replace ignition coil if it is pressed out."

3. "Connect BMW Service Tester on diagnosis socket. Run engine test step 09. Observe oscilloscope - ignition voltage = 6 to 14 kV. Check ignition voltage deviation = < 3 kV."