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Thread: Resistance of ignition coils

  1. #1
    Join Date
    Aug 2005
    Posts
    593

    Default Resistance of ignition coils

    Bentley states the resistance of ignition coils to be 0.4-0.8 Ohms. That is for M50 2.5L engine.
    I measured resistance on my coils and they are about 1.4-1.5 ohms each. They don't differ in any way, pretty uniform for all the coils. My engine is M50 2.0L. Coils are Brembi.

    Anyone can explain me why there is such a descripancy?
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

  2. #2
    Join Date
    Jan 2004
    Location
    Lexington, Kentucky
    Posts
    2,561

    Default

    Quality of measuring device? Perhaps the most telling point is how similar all the coils are reading. It would seem to indicate all all good or perhaps all are worn out. DUH! Even so, if the engine is running well, my assumption is the coils are good.
    Thanks,

    1995 525i Auto, M50TU 2.5L, EAT chip, 1/95 build, USA, 205/65/15 tires, ASC+T, HID, lumbar, EC Mirror, BMW Alpine 5 radio with BMW-Pioneer CD Changer, abt 236k miles, Oxford Green/Parchment

  3. #3
    Join Date
    Aug 2005
    Posts
    593

    Default

    Well the measuring device is a chinese made and a very cheap digital multimeter. Its not the most precise device in the world, but so far had been giving good readings. For example the throttle position sensor range had been 1.3 to about 4.3 kOhms, as it should be (approximately). Temp sensor reading was 2.4 Ohms (at about 30C), also OK. Measured a used ICV valve, got exactly the readings suggested by Bentley.

    But in this case the resistance of a coil is way off mark. There is a big difference between 0.4 to 0.8 ohms and 1.4 ohms.
    1994 520i with M50 engine, manual transmission and air conditioner.
    VIN: GG45422

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