Hey fellows. I have a question I hope y’all can help me with. On my 77 C10, the heater is the factory set up. When I bought the truck and started working on it, the heater fan (under the hood) was disconnected. I just plugged up the single wire into the fan unit and it works on high only. Inside the cab I have the factory 3 fan speed choice. My question is: Is there a relay in the circuit that lets you choose fan speeds, or is the fan itself a 3 speed unit? I am a fairly good mechanic, but have no sense of electrical systems at all! Thanks in advance👍
