i have a 70 chevelle and i can not get any power to my heater fan. at the heater switch i see three wires. a orange wire wich is hot. a purple wire that goes to the fan and blue wire that goes to the ac heater control in the dash. is the blue wire a hot wire? and also ther is not current going to my heater ac control. can this posibly be the heater switch under the hood? i a havr checked all fuses and connections

No ground wire?

if you look in the factory service manual (available on CD or paper) it has a wiring diagram for this.

The control head has a brown wire, power from the fuse, that connects to a switch operated by the top control lever. With the lever in the off position the switch is open, all other positions the switch is closed. When closed power is sent to the speed switch on the tan wire, When the switch is in the low speed position power is connoted to the yellow wire, med1 puts power on the ltgreen wire. med 2 puts power on the ltblue (these three wires are routed to the speed resistor) and hi puts power on the dkblue wire (the dkblue wire operates the high speed relay). The high speed relay gets power from the horn relay through the orange wire. When the relay operates (power on the dk blue wire) power from the orange wire is sent directly to the blower bypassing the speed resistors. The blower and the high speed relay both have a black , ground, wire that is attached to the firewall just above the relay.

thank you very much. the relay is not grounded i will try to ground it and see what happens

Relay not grounded would only affect high speed.

I don't mean to hijack this thread, but what does the brown wire connect to specifically, after it comes off the back of the heater controls ?
I see the lead is only a few inches long and then has another connector.

Nate