Escort ZX2 Electrical Problems

I have a 1998 Escort ZX2 with the 2.0 DOHC Zetec Engine. The temp gauge is stuck way past hot and the electric radiator fan is only working sometimes. I've checked the fan motor by hooking it up direct and both speeds are working. I've checked the temp sending unit and the resistance matches whats listed in the Haynes manual from 60-212 degrees. The manual mentions a constant control relay but without any specific information as to where it's located or how to check it out. Other noteworthy facts are: the A/C compressor doesn't always come on when A/C or defrost is selected and the car only overheats when driven in town when the fan decides not to function so I don't think there is a cooling system problem. My questions are where is the constant control relay, does it control temp gauge, cooling fan and A/C compressor operation and is there a test procedure for it or do I have to just stick a new one in and hope for the best?

I have the same problem did you figure this out i think it is the temp gauge but don't know and they are not cheap to change if your not sure