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I’ve only owned my 79 Corvette for a month or so. And I’ve only just noticed if I put the car in auxiliary mode, I hear some type of fan or something running on the right hand side behind the glove box. Does anyone know what this is?
"Aux Mode" could be IGN ON, but wasn't cranked, so the engine isn't running.
In either case, the blower fan is behind the glove box, and will run at low speed whenever the car is "ON". There is no way to turn it off without changing the stock wiring.
Is that what you hear? You should feel air coming through the vents.
From: Loud, Raw and Dangerous 1968 327 4S in Southern California
Originally Posted by Cain-25
I’ve only owned my 79 Corvette for a month or so. And I’ve only just noticed if I put the car in auxiliary mode, I hear some type of fan or something running on the right hand side behind the glove box. Does anyone know what this is?
Do you mean accessory mode rather than auxiliary? On my 1968 car that is when the ignition key is turned all the way counterclockwise. My blower speed switch for the heater has four positions including one where the fan is completely off regardless of key position.
Edit: Checked again and mine is definitely off...perhaps it has been modified or this was the way for first year's designs.
Last edited by Redvette2; Jul 7, 2025 at 08:58 PM.
Reason: Update...
Yes, anytime the ignition switch is in the ON position the blower motor will run on LOW speed.
Good or bad, the idea was to keep fresh air entering the cabin...
Now, if your inline Hot Water shutoff valve is faulty it will allow hot water to pass through your heater core resulting in higher cabin temps...
There is a easy electrical fix to stop the fan from running all the time if the car is optioned with A/C...
In the engine compartment there will be a fiberglass box containing the evaporator. On the top of that box you will see a 4 wire connector plugged into the Blower Resistor...
If you remove the Brown wire (Brown Arrow Circuit 50) from the connector you have bypassed the LOW speed of the Blower Motor...
If removed, you will want to put some electrical tape or shrink wrap on the now exposed F/M terminal as it is HOT when ignition switch is in the ON position...
The fan speed selector switch will still function normally...
My suggestion is whenever your ignition is in the ON position, let the blower fan run on low speed as designed. I have always thought that was a great idea. If the blower fan is making noise, like mine did, then replace the blower motor with a new unit. I did that and now my blower fan runs very quiet and smooth.
Having said that, it is nice to learn how to turn off the continuous running mode if desired.
Yes, anytime the ignition switch is in the ON position the blower motor will run on LOW speed.
Good or bad, the idea was to keep fresh air entering the cabin...
Now, if your inline Hot Water shutoff valve is faulty it will allow hot water to pass through your heater core resulting in higher cabin temps...
There is a easy electrical fix to stop the fan from running all the time if the car is optioned with A/C...
In the engine compartment there will be a fiberglass box containing the evaporator. On the top of that box you will see a 4 wire connector plugged into the Blower Resistor...
If you remove the Brown wire (Brown Arrow Circuit 50) from the connector you have bypassed the LOW speed of the Blower Motor...
If removed, you will want to put some electrical tape or shrink wrap on the now exposed F/M terminal as it is HOT when ignition switch is in the ON position...
The fan speed selector switch will still function normally...
That's awesome! I'll cut that wire out. It was 93' today and I was getting hit with random hot air from the vents. I have an AC car but the compressor has been removed. Do I need to replace the hot water inline valve now? Or should I do it whenever we decide to install the AC system. We drive regularly in the winter in Atlanta, never had an issue with the heater. Thanks Joe!
Lots of extraneous sources of heat getting into a C3 cabin besides hot water in a non-activated heater. Do some research and address all of the 'big hitters' to minimize cabin hear.
Aux mode noise.
