I m reinstalling the original a/c system unit under the dash after the components were removed 20 plus years ago but the system sealed. The under dash box was taken apart and stored. I've put it back together, blew the evaporator clean, replaced the expansion valve, drier, hoses and had the blower motor rewound. It will remain R12.
I have the under dash unit on the bench and I wanted to check the operation of the controls as I put this back together with no manual. With unit grounded and hooked up to the battery, I have all controls off. If I turn on the fan, I get all three speeds. If I turn the second control on, it shuts the blower off- whether it's city or highway setting. When I turn it off, the blower goes back on. The little blue light does not go on.
It's a lot of work reinstalling under the dash I'd prefer to do it only once. There is a second less heavy Guage get wire that exits the firewall and goes into the engine compartment. Maybe once installed and connected it should work..... I'm concerned with the fan turning off when I turn the second switch on.
I hope this makes sense as I describe this. My initial thought is this switch might be bad that turns the compressor on. Please give me your $0.02