Plug wire resistance when hot vs cold?
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Le Mans Master
Joined: Feb 2002
Posts: 7,858
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Plug wire resistance when hot vs cold?
Does the resistance of a spark plug wire increase or decrease when the wire heats up from engine compartment heat soak? Referring to both the stock carbon cord type wires and after market spiral wound (RFI/EMI supressor) stainless steel conductor type.
This is likely Electricity 101, but I'm stupid in that regard, so...
This is likely Electricity 101, but I'm stupid in that regard, so...
Tech Contributor
Joined: Jun 2004
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From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by Lone Ranger
Does the resistance of a spark plug wire increase or decrease when the wire heats up from engine compartment heat soak? Referring to both the stock carbon cord type wires and after market spiral wound (RFI/EMI supressor) stainless steel conductor type.
This is likely Electricity 101, but I'm stupid in that regard, so...
This is likely Electricity 101, but I'm stupid in that regard, so...
Tech Contributor
Joined: Jun 2004
Posts: 20,910
Likes: 962
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by GONE99
Resistive core wires ( low buck, standard replacement ) resistance will increase with increased temperature. Spiral core wires such as MOROSO will not.
Le Mans Master
Joined: Jan 2006
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From: Orlando FL
It is true that resistance increases with temperature for most items with positive temperature coefficients. Some special devices like some resistors have negative temperature coefficients in the design. Some resistors are designed to vary a great deal in resistance in regard to temperature. Some these sensors in the car feed the PCM/ECM, CCM and other devices.
Wires on the other hand are not designed to change resistance appreciably with temperature. A slight increase would be normal but a large jump in resistive value would be out of the ordinary and would probably be a bad wire. Now we haven’t talked numbers yet so until we know the difference in measurements (with temperature) its hard to say if you are having a problem.
Wires on the other hand are not designed to change resistance appreciably with temperature. A slight increase would be normal but a large jump in resistive value would be out of the ordinary and would probably be a bad wire. Now we haven’t talked numbers yet so until we know the difference in measurements (with temperature) its hard to say if you are having a problem.
