Question about the AC switch operation

[Bmachine]

I am trying to bring my AC back to life. I have a new compressor and new condenser but I have not hooked anything up yet. But I am testing the controls on the center console. And I cannot remember how the rotary AC switch is supposed to work.

When the switch is all the way counterclockwise, there is a detent which evidently signals that the whole AC thing is off. At that point, the regular fan above the firewall can be operated.

If I turn the AC switch clockwise, once it clicks past that detent, the regular fan shuts off and it seems that nothing happens until that switch is rotated all the way to the right. At the end of its rotation, there is another detent/click and then the fan in the AC unit in the center console turns on.

Is that the way it is supposed to work? I thought that once it got past the "off" detent on the left the AC fan speed would slowly increase until all the way clockwise.

And what is the purpose of the detent at the end? It is obviously an on/off switch of some sort. Does that switch the compressor on/off? If so, that would mean that no cool air is generated until the AC switch is all the way to the right.

Thank you.

 

[sfdon]

Look at the pic in the schematic- you will see how it works.

Off
On Variable
On Full

Sounds like a bad switch

 

[Bmachine]

On Variable

Thanks Don. That's what I thought.

OK, can these switches be opened, cleaned and brought back to life? Or do I need to get a new one?

 

[sfdon]

I have never fixed one.
2 different versions.
Early and late.

 

[Bmachine]

Gotcha. '74 here so I assume it is "late" version.

I'm assuming they operate in the way the old style potentiometers / variable resistors do. So I'll start by trying to shoot some CRC contact cleaner in there first to see if that helps.

 

[sfdon]

It’s usually a cracked ceramic switch body. Trash....
Carl and I both have them in stock. NOS

Here’s a nice Ac schematic...

 

[Bmachine]

Very helpful! Thanks Don.

 

[Stevehose]

I've repaired a non operating reostat portion of the switch. Electric cleaner/lubricant and some fine sand paper to clean the coil that the wiper arm goes over. If it isn't cracked like Don mentions then perhaps this can be brought back to life. After the full counterclockwise detent, once you turn it clockwise it goes along the reostat coil, if working it will gradually increase the fan speed until the next detent. Then once more clockwise to the last detent for full speed.

 

[Bmachine]

I've repaired a non operating reostat porrtion of the switch. Electric cleaner/lubricant and some fine sand paper to clean the coil that the wiper arm goes over. If it isn't cracked like Don mentions then perhaps this can be brought back to life. After the full counterclockwise detent, once you turn it clockwise it goes along the reostat coil, if working it will gradually increase the fan speed untill the next detent. Then once more closckwise to the last detent for full speed.

That's what I thought. Great to hear it could be repaired. Thanks Steve.