No “off” option for heater fan?

[evan]

My ‘78 had off as one of the options on the fan speed switch but my ‘79 only has low-medium-high. Even with the temp switch slid all the way to the cold side it still pushes air hotter than outside continuously. Is there an easy way to add an “off” option to that switch?

[geezer#99]

Might not be the fan.
Might be one of the doors(flaps) isn’t closing or opening like it should.
Check to see if they do when you adjust the controls.

[MJN]

If you have controls like this the top lever will shut off the fan in the 'off' position but you will still have air flow while driving.

If you are still getting only hot air then it sounds like a blend door issue or the control cable needs to be adjusted.
http://www.73-87chevytrucks.com/tech...ice_Manual.pdf

[kglowacky]

i
my 78 with air has no off-fan position also, I disconnected the yellow wire in the engine compartment on the heater box. Nowhen it is in the low position it is off, now I can shut off the fan . The yellow wire is the low speed for the blower motor

[franken]

73 and up had no wing windows so they made the fan blow a little to keep air moving. It's a feature not a defect.
You want the fan to be off, put in a switch.

[Bandit130]

Originally Posted by kglowacky

i
my 78 with air has no off-fan position also, I disconnected the yellow wire in the engine compartment on the heater box. Now when it is in the low position it is off, now I can shut off the fan . The yellow wire is the low speed for the blower motor

The fan will run on low all the time regardless of any position settings. I found this out about 3 years ago. You are right. The yellow wire at the resistor is for the low speed fan.

[Dead Parrot]

IIRC - AC trucks have the 'no off' feature. I think the thought was to ensure some fresh air getting into the cab to avoid CO issues. Heater only trucks have the two kick panel side vents and guessing the assumption was they or the windows would be open during hot weather and the heater running with some vent air mix during cooler weather.

2nd the thought to double check the heat flap cable adjustment.

Another way to keep low speed and have an off setting would be to install a switch on the ground wire from the blower motor. It would need to be a heavy duty switch.

[MJN]

A/C system operation table and standard C/K heater air flow outline. Based on the air flow outline on how it is supposed to work your purge door is not closing off air flow to the heater core- need to adjust the cable or investigate why the door is not closing. The last line is key 'The temperature of the outlet air is dependent on the ratio of heated to unheated air (controlled by the temperature door).'
http://www.73-87chevytrucks.com/tech...ice_Manual.pdf

[karlbenz]

I put a ball valve on my heater hose. Turn it off in the warm/hot months

[Warrens69GMC]

I unplug it during summer.

[kipps]

Originally Posted by franken

73 and up had no wing windows so they made the fan blow a little to keep air moving. It's a feature not a defect.
You want the fan to be off, put in a switch.

Huh?!? Every 73-87 squarebody left the factory with wing windows.

[straight6chevyguy]

Originally Posted by kipps

Huh?!? Every 73-87 squarebody left the factory with wing windows.

Me thinking the exact same thing

[VWNate1]

After several decades of ownership I finally got tired of that warm/hot air blowing in all the time and decided to chase it down .

Turns out that from new the fresh air flap's Bowden cable was incorrectly installed .

I removed it and lubricated it until it slides easily even when held in a loop, re installed it so the diverter flap is fully closed when it's supposed to be and Lo ! .

It's far more comfy in the cab in warm or hot weather .

As as result I'm fixing the A/C , might as well .

[hatzie]

The blower doesn't have an off position just LOW - HIGH