Mr. Landry is correct. If you already HAVE a Start Device, another won't make startup any better. Diagram posted above shows a Relay in the Start Capacitor circuit. If that setup is in fact installed and working properly, it should actually perform a little better than SPP6e. Relay Type OR SPP6e will outperform a PTCR start assist or SPP6 (no "e") which is also PTCR. This from Chris Bryant, another contributing guru here. In his shop, he installs SPP6e and is aware of SUPCO's comments. I read somewhere, and Chris has mentioned, there is also a start kit from Dometic that is supposed to do a little better than the rest. By better I trust that means gets compressor going started quickest and/or with least current draw.