strange oven controller!

I have a 1990 Jenn-air electric oven. Robertshaw controller. The oven control works fine. The oven will not self clean as the broiler element shuts off before the oven reaches cleaning temperature. The broiler element doe sabout 60% of the heat for cleaning. It is not ( replaced with new ) the oven sensor or the over temp protoective switch ( bypassed) . My assumption is that the controller has somehow set the max temp to a much lower temperature than the cleaning cycle temp of around 900F. Has anyone worked on these 1990 controllers and if so do you have ideas as to how to reprogram the set points? Help please.