Trouble with A/C system...

2013 DC, new filter and good charge and yes the A/C works on all speeds...

On 2 separate occasions I have had the A/C fan output drop by about half of the normal output. System continues to cool just fine but the amount of air that comes out is about half at all settings. Both times i was driving the truck for about an hour. Once I let the truck sit (motor off) for about 15-20 minutes or so there will be a larger than normal puddle of water under the truck. Once I turn the truck back on the A/C will then blow just fine. Strange I know, just wondering if anyone has any experience with this?

Almost seems as if something is freezing up, like a line or the evaporator core.

Thanks for any help in advance...

 

Look at the fan speed resistor. It'll be near the blower motor. Unplug it and look in the connector to see if any of the terminals are corroded. Check the blower motor and HVAC control connectors as well.

 

thanks will look into these three areas.

 

This.

These are notorious for resistor connection burnouts. You can clean them and slightly bend the pin closer to the connection but the long term fix is to buy a connector kit and splice a new one on.

 

Large puddle as the evap thaws. The termistor in the evap is not stopping the freeze-up. Next time it does it, leave the truck running and immediately pop the hood. Look at the larger AC line where it exits the firewall. See any frost/ice?

 

I've seen pix of where that is. Oh gawd. You might as well do the heater and evap cores while your there...

 

Will do the next time it does it. Can you elaborate a little on the Termistor in the evap?

 

The thermistor is just a temperature sensor that attaches to the evap. It's purpose is to shut off the compressor if the evap is freezing up, allowing it to defrost, then the compressor will come back on. It's a tear apart the dash job to get to.
@Jimmyh can explain the electrical part much better than I.

 

Sadly, that sounds like what is happening. The A/C has been unusually cold since the last time it acted up. I will look into this thermistor thingy.

 

In the meantime, when driving for an hour, turn off the AC for a few minutes every half hour. This will allow the evap to defrost and keep it from completely freezing up.
And something folks don't realize... ice expands as it freezes creating a lot of stress on the parts it is freezing on/IN. And that creates evap leaks.

 

Noted....actually started doing this yesterday. Appointment set up for tomorrow to have the system checked. Thanks btw

 

That can also happen from low charge or low airflow over the evaporator.

 

Not if the thermistor is doing it's job.

 

In my research today, i read this and really hope this is the issue. Hoping tomorrow will be a positive outcome.

 

This is really clear and helpful.

 

Exactly this. When the evaporator gets to the low set point the compressor clutch is dropped off until the temperature rises above high set point which allows the compressor clutch to reengage again... Repeat... in a continuous cycle as long as the AC is turned on.