The engine I put those 3.4 amp PTCs was my own and I know they would likely be too slow to open in case of a sudden lock up. I decided that risk was low and would likely only happen if something managed to get stuck in the gears. For someone else I would either use the low amp PTCs or just recommend a full blown Cruise Commander.
Just to elaborate on PTCs (Positive Temperature Coefficient thermistors), the resistance increases with temperature. For many thermistors the change is closer to linear, ie 10 degrees F might increase resistance by 10 ohms. These must be a special version which exhibit little change until the maximum current rating is reached and then suddenly have large increase in resistance.
Pete
