Can you check resistance in stock plug wires?

Leland Pate · 09-12-2001, 01:29 PM

I want to test my old stock ign. wires with a voltmeter. Can anyone tell me what kind of resistance reading I should be getting if they are still good? Thanks,

Ted Stringer · 09-12-2001, 01:35 PM

0 ohms is real good, I don't know if the 911 wires have a resistor in the plug side connector. if they do than they should read the value of the resistor.

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Ted Stringer
nuke3@juno.com
'84 911 Targa aka pocketrocket

Early_S_Man · 09-12-2001, 01:44 PM

Lee,

The wires can be tested, whole, as they come off the engine, end-to-end, and the value should be nominally in the range of 3000-5000 Ohms. Both ends unscrew from the wire ... some distributor cap ends have resistors of 1000 Ohms, and others have none, and thus 1 Ohm or slightly less would be normally expected without the resistor. The Beru spark plug connector can be either 3000 or 4000 Ohms, nominally, +/- 10%.

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Warren Hall
1973 911S Targa
1992 Dodge Dakota 5.2 4X4 parts hauler

Superman · 09-12-2001, 01:53 PM

Warren hit this nail on the head as usual. He also feels, though he did not mention it, that the Beru connectors can perform poorly at high temps. So, another test would be to warm them up and see if they behave differently.

Also, resistance is not particularly important. Resistance is designed into these systems to avoid radio interference.

So in other words, if your cables do conduct electricity, then they should work. Actually, if you test resistance, the thing to look for is a cable that does not act like the others.

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'83 SC

stlrj · 09-13-2001, 09:48 AM

Regardless of your resistance readings, if there is crack anywhere that you cannot see, your readings would be meaningless.

A better test would be to load your cables with at least 25KV on your engine and check for shorts.

Joe