I loop my installs and have consistent voltage but many times I come across other system that are not looped with bad voltage ranges (14 volts down to 9). I solder my connections and once the wires get carbon buildup the flux and solder doesn't work very well. I've tried to scuff the wires with sand paper clean off carbon but it really doesn't help. I'm uncertain if the carbon is strictly a product of excessive voltage or a combination of excess voltage being pushed (amps) to great a distance. I'd like to hear others feedback on the issue.