64 AC fan switch question

[Deanoko]

I just had a really knowledgeable mech friend evacuate and charge the AC system with 134a.  It's blowing cold, however the AC blower fan switch is inop, but I can use the heater fan switch (with other heater controls off to get the vacuum door logic to work)  as a backup.  

Other than the actual component switch being bad, does anyone have any other ideas?  

Also, are the 2 switches the same or specific? Do they command the same actual fan speeds in either AC or heater mode?

I don't get why there are 2 switches in the first place! 

Thanks! 

[XframeFX]

What year?

My '63 w/AC has 2.

Kongaman wrote up a mod to enable High Fan Speed on both switches. I studied that and the Shop Manual on AC.

Study the Shop Manual. I did a while back but need a refresher.

[Deanoko]

Yeah.  I'm looking at those resources.  The thread title said '64...

I blew up a wiring diagram to 2'x3' and have it hanging on my wall.  

My system has 2 fan switches, but the wiring diagram only shows 1.  Hmm. 

[1965rivgs]

  There are  master switches inside the control head for both the heater and AC blower switches that supply voltage to the switches which are on the face of the control head. The master switches are off when the slide levers are off / to the left.... and turn on when the slide levers are moved from the off position to the right.

  The blower speeds don't coincide between the heat and AC switches. Only the AC switch engages the high blower relay on the passenger's fenderwell to provide high blower speed with no deliberate resistance in the circuit. The modification to the wiring mentioned is to obtain high blower speed via the heater switch, not really needed unless one is operating the car in winter like conditions, because the system as designed is somewhat lacking in performance re the heat/defrost functions.

  The heater and AC blower switches are different. In addition to controlling blower speed, the AC switch also actuates a lever on the rear of the control head which actuates a cam via a connecting wire. The cam completely cuts off vacuum from the vacuum regulator when in high blower position. This brings the vacuum level to the vacuum diaphragm in the STV valve to/or very near zero and enables full cooling from the refrigerant system.

 

Tom Mooney

Edited May 26, 2023 by 1965rivgs (see edit history)

[Deanoko]

Excellent info Tom.  I need to digest it all, and revisit my wall size wiring diagram.

Thanks! 

[1965rivgs]

7 hours ago, Deanoko said:

Excellent info Tom.  I need to digest it all, and revisit my wall size wiring diagram.

Thanks! 

  There is an isolated blower control schematic in the optional A/C section in the shop manual. If memory serves well the lever controlled switches are called "heater control switch" and "circuit control switch".

Tom

[Deanoko]

I haven't pulled the lever knobs off to access behind the face plate yet.  Maybe something physical will present itself then.

They all traverse freely enough for 59 year old mechanicals. 

[1965rivgs]

40 minutes ago, Deanoko said:

I haven't pulled the lever knobs off to access behind the face plate yet.  Maybe something physical will present itself then.

They all traverse freely enough for 59 year old mechanicals. 

Don't pull the knobs...that will get you nowhere. You need to access the rear of the control head to use a test light on the wiring or switches.

Tom

[Deanoko]

Oh, OK   Thanks for saving me from going down the wrong rabbit hole.

 

[gungeey]

When you say "inop" do you mean the switch is bound up?

If so, your problem is likely not the switch but the cable that is attached to your AC blower switch has failed/flexed/bound. Or even a second cable (B) that attaches to the cable pictured(A)

 

Overengineering at its mightiest 😆 

 

Edited May 28, 2023 by gungeey (see edit history)

[Deanoko]

No, the switch moves freely, clicking through the settings.  It just doesn't actuate the blower motor. 

[1965rivgs]

1 hour ago, gungeey said:

When you say "inop" do you mean the switch is bound up?

If so, your problem is likely not the switch but the cable that is attached to your AC blower switch has failed/flexed/bound. Or even a second cable (B) that attaches to the cable pictured(A)

 

Overengineering at its mightiest 😆 

 

That is the wire I mentioned which connects to the cam which closes the vacuum modulator in high blower position.

Tom

[XframeFX]

On 5/27/2023 at 10:45 PM, Deanoko said:

I need to digest it all, and revisit my wall size wiring diagram.

So, 1964 Controls

With so much Forum dialogue on 1st Gen AC, I still need to digest more to see if I can clean up the original Controls with my own design. Otherwise, continue with the vacuum actuator design by restoring to original.

I do want to replace Fan Switches and resistors in the duct work with an efficient PWM Fan Controller. However, all HVAC except a problematic Heater Core are at the bottom of my list.