Question about Coil Resistance -Ohms
03-14-2007, 05:15 PM
#1
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Question about Coil Resistance -Ohms
Was wondering if anyone can help.
FSM indicates Primary Coil Resistance (Cold) should be between .36 and .55 ohms.
I've checked 4 used coils 3 of which work and 1 of which doesn't and they all read .7 ohms.
Anyone else run into this?
FSM indicates Primary Coil Resistance (Cold) should be between .36 and .55 ohms.
I've checked 4 used coils 3 of which work and 1 of which doesn't and they all read .7 ohms.
Anyone else run into this?
03-14-2007, 11:28 PM
#2
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Ohm testing of most automotive circuits is basically useless. The circuit needs a load on it (ie amperage) to test it's integrity. The best ways to check a coil is to a) current ramp it b) Ignition scope pattern c) spark tester. The resistance check is only good for checking to see if the coil is completely shorted or open. Most coil failures are due to weak insulation internally, but the insulation doesn't break down till several hundred volts are built up.
03-15-2007, 06:54 AM
#3
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Did you check the resistance between your meter leads? My $20 walmart meter has about .5ohm between the leads, which you have to account for in your testing.
03-15-2007, 12:23 PM
#4
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This confirms what I suspected. The ohms test sucks, considering my known bad coil checks out ok.
Good thing I have lots of coils to throw at it.
Good thing I have lots of coils to throw at it.
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