What;s Wrong With My RAM Truck????

[mustang071]

Our 2005 Ram 3500 Diesel (5.9) SRW has been a great tow vehicle for our 7-ton 5th wheel trailer. And after 150 thousand miles, three years ago we had to replace a couple of leaky hoses in our air conditioner. No surprise there. Since that repair, the AC blows cold and steady, towing or not. EXCEPT.

During this past year, on our last three return trips to Texas- one from the Great Lakes and two from Colorado- the blower quits working at about 350 miles from home. The AC is constantly cold, but without the fan blowing, we get very uncomfortable and downright HOT in the cab driving home in the Texas heat. In fact, on the last two trips, the blower quit in exactly the same place, a few miles south of Amarillo heading down 287 towards Dallas.

Each time, we’ve managed to get a little action out of the AC fan IF we can keep the RPM high as we travel. But if we stop at a red light and the engine is at idle, we get nothing. Cracking the window seems to help the blower also, but engine speed seems to be the key. Once on our last trip when climbing a hill, the tranny dropped to low and the fan started working perfectly as the RPM climbed to about 3000. But that lasted for about 3 minutes before dropping back into pathetic, weeny mode.

The Dodge House is clueless; they said the system only needed service which was performed prior to our most recent travel, but that had no positive effect on this fan problem. The AC works perfectly around town and all during the trip, except for the very last 350 miles.
Has anyone out there in RV land had this issue? If so, how did you fix it? Help!

[mustang071]

Thanks to all of you for the replies.

The Dodge Tech (thinking a freeze-up) suggested low Freon and serviced the system. Then said if the problem continued to stop and let it sit for awhile before restarting. We did all that, but it had no positive effect. And, as far as I can tell, the blower motor continues to run but the airflow diminishes to almost nothing at low RPM.

The strange thing to me is that it doesn't do this any other time except the very end of our trips. Why wouldn't it happen when we started out or during the entire excursion of two weeks?

[gkainz]

Blend door failure was a recurring theme for a while on the 2nd and 3rd gen RAMs but I thought they were a "broke and stayed broke" problem, not one that works for a while and then doesn't.

[Huntindog]

Moser wrote:
I have the same year truck, the problem that is common with those is the door to recirculate the air will break. My fan worked fine, however there was insufficient cooling, thought it needed recharging, had it checked and that was fine. I came across other people having this issue, I checked the door and found mine had broken and was not allowing the air through. I removed the door and it has worked perfect since. Plan on replacing it someday. It is easy to check, remove the glovebox and you will be able to see the door. You should be able to see if it moves by putting the AC on max.

I would agree to that possibility, except it works great for long stretches of time. That points to a freeze up. Possible other parts would be resistors etc... But the same detractor from that thinking is again.... It works great for long periods of time.

[Huntindog]

Iraqvet05 wrote:
I had a 2500HD that would stop blowing cold air at stop lights and at low speeds. The blower fan would still blow but the air was hot. It took me a few weeks of research but I found out the fan clutch had failed, causing the evaporator to freeze up.

I cannot fathom how that could be.
A clutch that doesn't engage with enough force (normal wear failure) will not pump enough freon to freeze the evap.

One that has locked up (Not a normal occurance) will be much more likely to freeze at highway speed... In fact most systems cannot make a evap freeze at idle. They just do not pump enough freon fast enough for this to occur.

[Moser]

I have the same year truck, the problem that is common with those is the door to recirculate the air will break. My fan worked fine, however there was insufficient cooling, thought it needed recharging, had it checked and that was fine. I came across other people having this issue, I checked the door and found mine had broken and was not allowing the air through. I removed the door and it has worked perfect since. Plan on replacing it someday. It is easy to check, remove the glovebox and you will be able to see the door. You should be able to see if it moves by putting the AC on max.

[mich800]

If it is the fan that is the issue trying to diagnose the AC is just over complicating it. It would do the same thing on heat. Could be switch, wiring, resistor or fan motor. Time to get the meter out. I am leaning towards the fan motor as a bad resistor will typically allow full fan speed but nothing lower.

This is assuming manual hvac controls and no auto climate control and the fan is not running. But not necessarily clear from the OP.

[beergardens]

It isn’t clear in the original post whether the blower motor actually quits running, or if it continues to run but the airflow diminishes. Determining this is a key part of diagnosing this.

[Iraqvet05]

I had a 2500HD that would stop blowing cold air at stop lights and at low speeds. The blower fan would still blow but the air was hot. It took me a few weeks of research but I found out the fan clutch had failed, causing the evaporator to freeze up.

[dodge_guy]

Fans And blower resistors are common in those year trucks. I've also run across a few that had a burnt connector under the TIPM (underwood fuse box). Should be a simple problem to find.

[SweetLou]

What does it do if you pull over, turn off the truck for a few minutes, then start it up again? If it blows normal, then what ever electrically resets the blend door is your issue. I have had that now in 2 Rams and a 2 Fords

[GordonThree]

ScottG wrote:
Sounds like low freon level is causing the evaporator coil to freeze up.
It will be worse when humidity is high or eng speed is low.

I don't know about freon level but I agree sounds like the evaporator is freezing up.

I have seen this in a fleet I support, but they're F150s. AC works great for a bit and slowly fades to nothing.

[Huntindog]

DP

[Huntindog]

ScottG wrote:
Sounds like low freon level is causing the evaporator coil to freeze up.
It will be worse when humidity is high or eng speed is low.

Highly unlikely. Low freon level would result in poor performance. The system blows cold. Therefore, the freon level is perfect, or close to it.

You may be on to something with the icing of the evaporator idea though. The system should have some sort of switch (probably a low pressure or temp) that cuts the compressor off to prevent this.
In my mind this is the most likely cause. The OP can test his theory out without any tools or even lifting the hood. When it happens, simply turn the AC of for a few mimutes. If it is iceing, then it will melt, then work perfectly when it is turned back on, until it ices up again.

I am not sure if this is a orfice tube or expansion valve system.

If it is an expansion valve system, then that may be acting up.
This is a more involved fix though.

I would look for a compressor cutout switch. They are cheap at 15.00 or so, and easy (5 min) to install.

[ScottG]

Sounds like low freon level is causing the evaporator coil to freeze up.
It will be worse when humidity is high or eng speed is low.

[ib516]

I'd try a new blower fan/motor assembly. They aren't very expensive, and super easy to change out. A few screws under the dash and it's out. Could also be the resistor/fan speed control. That is also easily accessible right beside the blower. 1AAuto.com has a video on it if you're not handy.