I purchased a Ritetemp Thermostat model #8035c. The HVAC system installed in my condo is forced air furnace heat/electric compressor cooling and was manufactured by Gaffers & Sattlers (circa 1973).

Any guidance on how to connect the wires to the thermostat is greatly appreciated.

There are four wires encased in PVC jacket.
1 Red
1 White
1 Yellow
1 Blue

There's a separate yellow wire with 2 feeds.
There's a separate brown wire, but capped and taped off.

labman

Does the thermostat have terminals marked Y, G, W, and R or RC? Would you believe it is as simple as connecting the yellow wire to the Y terminal, the red to the R, jumpering it to an RC if any, etc. If the thermostat doesn't have those standard markings, you will need to study any instructions that came with it or check with the manufacturer for which terminals do what. Then follow the conventions below.

Usually there is a 24 volt AC transformer in the furnace with the secondary winding connected to a red wire running to the thermostat and a blue wire, common, to the gas valve, A/C relay, and fan relay. From the thermostat there will be white wire to the gas valve, yellow to the A/C, and green to the fan. The thermostat is wired to switch the power from the red to the white, yellow, and green as needed with the blue completing the circuit. Most thermostats and furnaces have the contacts labeled R, B or C, W, Y, and G for the corresponding wire colors. It may be wired to have the A/C control wires return to the furnace and its controls and then a second wire goes to the A/C unit. Internal wiring may replace the green wire if the thermostat does not give you the option of fan only or continuous fan. Digital or programmable thermostats may need the blue wire connected to them.