1978 A/C Blower Motor Switch?

[Garys78T/A]

I am new to this Firebird stuff and exactly what does what! I am restoring the A/C system and have replaced the evaporator box, resistor, relay, heater box restored, and blower motor; I think that about handles it.

I am not running a compressor yet, but I have the ground going to it from the harness dialed in on a chassis ground.

My fan works and has 3 speeds.

My problem is the fan shuts off when I put it on "HI"?

I was told these systems do not have an "OFF" position.

I am unsure if I need to keep searching for the problem of the switch not working correctly or if it is possibly a fusible link that may not let the relay work on the "HI" setting.

Any help would be greatly appreciated. Thank you

 

[Aus78Formula]

The fan not working on high is a wiring issue.

A separate power feed bypasses the resistors and gives a full 12v when selected on high.

It may be an incomplete setup since, on some models, selecting high speed would also run through the Max cooling AC setting.

Do you have a workshop manual or wiring diagram?

Possibly also a faulty switch on that speed, but not the usual issues.

 

[Garys78T/A]

I will check that the relay is not inhibited by power.

I'm still curious if the switch is supposed to completely stop the blower motor from running.

Do you know?

 

[Aus78Formula]

In the simplified color diagram, we can see the high-speed setting is full power direct to relay, with no resistors to limit before the fan.

Check the plugs, and maybe get a test light to see if power is getting to the relay on that wire or out of the switch.

It could be a faulty relay, too.

There is no off switch for the fan; it runs continuously.

There hasn't been an offsetting since about 72, and with non-AC, all models with AC.

 

[Garys78T/A]

Thank you, thank you

I am slowly figuring this out with the help from you and others. My engine harness was the key to power my Hi speed blower switch. Since I don't have a compressor to look at, I am trying to figure which harness I will need to jump power from the engine harness to the AC harness Hi speed blower? As for now, I jumped it with a temporary wire and it works, yay! I am not going to run any of the idle solenoids on my carburetor. I can't find good enough pics from the aftermarket companies to decipher what I actually need. Thanks again!!