Hey!
Have an 03 screw lariat with the auto climate control.
Truck has good heat till you drive for about an hour then nothing comes from the vents.Temp controls work and i can change to the other modes and hear the change,but no air movement from any vents.
The pass top of the dash gets hot and you can hear the air rushing around there.
Shut the truck off for 45-1hr and fine again.
Anyone have a similar problem or point me in the next direction?
Thanks

 

Sounds like a control head problem with the climate control. If thats the problem the control head is around 400.00 so make sure thats it before buying a new one.

Symptom Chart :

No communication with the electronic automatic temperature control (EATC) module
1.Circuitry short/open.
2. EATC module communication network.


The EATC system is inoperative, intermittent or incorrect operation
1.Circuitry short/open.
2.Input sensor(s)/erratic input signals.
3.Charging system.
4.Automatic temperature control sensor hose and elbow



Incorrect/erratic direction of airflow from outlet — EATC
1.No vacuum to the A/C control
2.Function selector switch
3.Vacuum hose/kinked/pinched.
4.Airflow door binding/stuck.
5.Vacuum control motor
6.A/C vacuum check valve
7.A/C vacuum reservoir tank and bracket
8.Vacuum actuator arm not connected to the door crank.
9.Heater control valve leaks vacuum.


Insufficient, erratic, or no heat
1.Low engine coolant level.
2.Engine overheating.
3.Plugged or partially plugged heater core
4.Temperature blend door binding/stuck.
5.Temperature blend door actuator
6.Incorrect heater control valve operation.

 

I doubt there's anything wrong with the control head.

Sounds more like the evaporator is freezing up. There are no directional doors tat can completely stop airflow if any are in the wrong position in any incorrect combination, so therefore, the only thing that is possible is for something that IS common to all airflow must be obstructing airflow. Only the evaporator core meets this condition.

Most EATC modes (except VENT and FLOOR) run the A/C compressor.

I'd bet that if the truck were parked immediately when the symptom occurred, there would be a very large puddle of water under the truck an hour or so later (depending on the ambient temp). If so, that would confirm the evap freezeup.

Evaporator freeze-up is usually caused by a pressure cycling switch that is stuck in the CLOSED position causing the compressor to run continuously instead of cycling off and on.

$15 dollar part that takes 5 minutes to replace.

Steve

 

Is there any way of testing the switch,or just replace it?
The A/C was topped of mid summer.It has been below freezing here,so i probably won't get much for water when i park it.
Thanks.

 

For testing purposes, I'd just unplug either the cycling switch or the compressor. If you don't loose your airflow as previously, then you'll know that the compressor has been running continuously. Just keep in mind that without the compressor, the clearing of window fog becomes more difficult, especially in cool, wet weather.

The cycling switch screws into the top of the accumulator can which is mounted on the firewall next to the cover over the mega-fuses and the starter relay.

Steve

 

Thanks.
I will try unplugging the comp. and see what happens.

 

might also be a vacuum problem. I took my car in to get a cd player installed, on the way back i tried to change the vents and nothing happened, i took it back and got it fixed, the guy said that it wasnt sealed properly.

 

No. Not possible. See post # 3 above.

Steve

 

I unplugged the comp. and took a 7 hour trip yesterday and had heat the whole time.
So looks like i will pick up a press. switch and change that.
Thanks for the info.Was nice having heat again.