As long as they're the same type of flexwatt, they should heat about the same. The only thing that is going to prevent them from working properly is a high resistant connection somewhere in the circuit. Make sure all of the connections are nice and tight. If you have a meter, hook up the leads from the meter to each of the cord's prongs. Measure the resistance in the troubled circuit, then measure a known good flexwatt system to see what the resistance is. Both should be realtively close to the same measurement. If not, check all of your connections again until you find the high resistant conncetion. I guess you could have a bad piece of flexwatt too, so check that too.

Good Luck!
Jim Smith