Help!!
I have a 99.
My heater and AC works fine for 2-2.5 hours of driving then slowly the air output goes down to almost nothing, doesn't matter where I put the control **** on, doesn't defalt to defrosters(wish it did). You can still hear the fanning running at the various speeds.
I thought I had a AC problem with the coils freezing up and slowing down the air flow but now that's it's turned cold I still have the same problem!
Stop the truck for a matter of hours and it works fine for a while and does it again.
Mark

 

If you have the selector in the defrost position, the A/C compressor is still running. You might have low freon. If you run it in any other position, does it work? Other than that, don't know but wish you luck.

Ed

 

I thought the AC charge was low and had it checked out it is fine.The thing just starts to slow down blowing air no matter what position I have the switch in, seems like something shifts to a position that shuts down the air flow after running for some time.
I was driving Friday through the snow storm that hit the midwest and defrosters wouldn't keep up, wouldn't blow enough.Today I drove for 5 hours and it worked fine for a change, but most of the time 2-2.5 hours is about all it works right.
I am wondering if a line starts to collapse when it gets warm but in that case shouldn't it go automatically to defrost?
Mark

 

you might have a vaccuum leak that over time of use causes it to shut down. the control of the a/c-heat system is vaccuum operated

 

I don't think it would be a vacume leak, he has control so it is hooked-up. I have compleatly disconected the vac line at the heater and the vac pump does such a good job it would still hold 16 inHg, It reads 25 normaly. I think it is electrical, and eighter the slector switch (fan control) or motor. I would start with the motor, they run dry after a while and do like you are describing. Usually the bushings dry out and as the motor runs it gets hot, finally it starts getting hot enough to tighten things up and slows down or stops. You may be able to spray some good electrical cleaners and then some lube for a quick fix. Good luck.

 

I'm with the low AC charge theory, if it keeps up try another shop.
Mine did exactly the same thing when the charge was low, iced up coil blocked airflow.

 

I have been having this problem since last summer.
I thought it was a low AC charge but it's where it shold be,
I haven't ruled out something wrong in the system causing it to freeze up, possibably some trash blocking the orfice slowing down the freon flow? I replaced the low pressure switch also.

I Just drove in last night (6.5 hours) and the heater worked fine, Murphys law- It will let me down when I get in a bad storm somewhere.

I will look into the fan, can anyone tell me the easiest way to get to it? I am home for the Christmas week and will try and get down to the bottom of this,

I still can hear the fan running without much airflow so I still think something is causing the flappers to shift to a position that stops the airflow.
Thanks,
Mark

 

If it's anything like my 2002, your fan motor is down by your passengers feet facing up. It is held on by 3 screws. Before you go that route, pull your glovebox door. Inside the glovebox opening you will see a vacume solenoid that opens your recirculating door. Pull the line that goes to your solenoid and see if you have any vacume. You may have to put it on 'MAX A/C' to get vacume there. Then open the recirculating door and see what happens different, if anything. Good luck.

 

One thing a lot of people dont know is that there is a resisitor that controls the fan motor speed and this seems to be a point of many heating and cooling problems it Dodge trucks. I think the replacement ones are a dealer only item bout $8.00.

 

I dropped out the motor and noticed it didn't spin very freely, the bottom end was very dirty, sprayed it out with some electrical cleaner and then you could see that it was the used brush material that falls down to the bottom bearing.
I couldn't see how much brush was left but there has to be a lot of wear.
I will lube it up tomorrow and see how long it lasts.
Hope this solves it!
Thanks,
Mark

 

I cleaned and lubed up the fan motor-it runs a lot quieter now a huge difference, seems to put out a lot more air flow also.
I was running the switch through the various positions and it stuck on blowing on the floor, seems like you can shut off the truck and start it back up and things work good for a while then slowly it starts blowing on the floor and stays there no matter what position you set it on. guess the next thing to do is replace the selector switch, can someone enlighten me on how to take it out of the dash?
Thanks,
Mark