Ventilation and A/C Fan Issues

[Wobdog]

Issue 1 – A/C Blower (Side Fan) Runs Constantly
When the ignition key is in the ACC position — even with both the main blower and A/C switch turned off — the A/C blower runs at a low speed.
It continues to run when the engine is started.
If I turn the A/C fan speed dial, the blower increases speed through the next two levels as expected.


Issue 2 – Main Blower Switch Doesn’t Hold High Speed
The main blower slide switch works in all three positions, but when moved fully to the right (high speed), it only stays at high speed while I hold the switch.
As soon as I release it, the fan drops back to the middle speed.

My gut is they are not related issues but would like input.

 

[HB Chris]

The a/c squirrel cage fan runs when the fan switch is turned on, not the temp switch, meaning it can run without a/c being on. Power comes from fuse to fan switch then to temp switch then to compressor. You must have a short of it runs when both fan and temp switches are both off.

The heater fan switch is a weak point as the rheostat portion becomes worn and contact is only made at the full speed end. At least you have middle speed but losing high speed is strange. The issues are not related. If the a/c fan is turned on the heater fan is disabled by the changeover relay attached to the fuse block.

 

[Wobdog]

The a/c squirrel cage fan runs when the fan switch is turned on, not the temp switch, meaning it can run without a/c being on. Power comes from fuse to fan switch then to temp switch then to compressor. You must have a short of it runs when both fan and temp switches are both off.

The heater fan switch is a weak point as the rheostat portion becomes worn and contact is only made at the full speed end. At least you have middle speed but losing high speed is strange. The issues are not related. If the a/c fan is turned on the heater fan is disabled by the changeover relay attached to the fuse block.

Great info, how do I fix it.

 

[sfdon]

Replace the AC fan switch