The one switch activates both the lower and upper elements. The thermostat bar is used to determine at what temperature the oven is at, if there is no thermostat, then the switch has a hard time determining a pre heated oven.
The thermostat is attached to the switch. If using the oven the way it is, no problem, and to answer your question, yes you can use the bottom element with out using the top element. If you want the broiler to work and to pre heat the oven, replace the switch, and then you can find out if the broiler is not working, or maybe its just the switch. One of my stoves I'm parting, out, I can get you a used switch with the thermostat and a used broiler also, its up to you, you can use the oven the way it is or if you get tired of the way it works, let me know. the used parts will be a lot cheaper than trying to locate new or rebuild the old, and it sounds like at this point it may not be worth it to you.
As you can see, by going on line, there are several Frigidaire Flair clubs and people ready to help. Theses stoves are becoming collectible, and they were built like a car so they seem to be lasting a lot longer than the new stoves.
The serial number you have provided tells me this, R for range, CI, for custom imperial, H is the year, 1964, and the 645 states it has the double ovens,\
Frigidaire produced these stoves from 1960 until 1968, sometimes you will see a V or EH which indicates it is a fan model, where it came with its own fan system located on top of the stove to catch all the fumes, through its own filter, like it had its own recycling system.
I am sure you just got your fill of information, be in touch if you need anything, thanks
Tom Nichols
From: "tjwe...@gmail.com" <tjwe...@gmail.com>
To: Frigidaire Flair <frigidai...@googlegroups.com>
Sent: Saturday, February 21, 2009 8:48:02 PM
Subject: [frigidaire-flair] Frigidaire Custom Imperial RCIH 645
While replacing the Oven baking element is it necessary to replace the
broiler element also ? The broiler element in the larger oven is not
working and the (t-stat ?) is no longer attached. Don't care if the
broiler works unless it has to !
Thanks,
TW - Mpls.