Okay, here's a stumper.

2004 RAM 1500 5.7 Quad cab. Great truck ... A/C works great, blows hard and cold, for about 45 minutes, and then the airflow out of the vents starts getting weaker, to the point where, about after an hour of use, no air comes out.

The fan spins just fine, but something is clogged down by the passenger footwell. When this happens, the underside of the HVAC box is wet with condensation.

After searching DodgeForum, and Youtube in general, all signs point to the recirc/blend door, except that IT LOOKS JUST FINE !!! (I took the blower motor, and looked).

If I let the truck sit for 20-30 minutes, and then get back on the road, the A/C starts blowing great again (for the next 45 minutes, anyway).

Anybody seen this before? It's a head-scratcher!

Thanks in advance!

vindio

 

Sounds like it's icing up. Could be over or under charged. Take it to a ac shop. Don't use that can crap.

 

That's a good lead ... question though: does that explain the weaker air flow out of the vents?

 

Yup, just like the ac in your house, ice blocks air flow thru the evap core.

 

As soon as the flow shuts down, turn off A/C and turn on the heat. If flow resumes in short order, it's icing up.

 

Thank you, both of you guys. Looking to have the system recharged up this week. Will report back!

v

 

Sound just like the problem I had in my 05 Durango iceing up and that is exactly what is happening and when it does it blocks the air flow until it deices.
On the durango there is a fix for this adding a resistor to a wire on the main control on the dash. Adding the resistor makes the compressor cycle on and off for a longer period to keep it from iceing up. I pulled the dash AC control found the wire added the resistor and all was good never had the problem again.

***Locate the evaporator temperature sensor signal wire its on the AC/Heater control panel you will need the wiring manual for your truck.
Then add a 470ohm resistor in line with the wire that is connected to the temp sensor signal wire. Cut wire and add 470 ohm resistor in line with this signal wire. This will make your compressor cycle off for a longer period and keep it from freezing.
You can also add a switch across this resistor to bypass it. Only need to do this if you want to so you dont have to take the AC control panel off again if something else is causing this. This info was taken from my Durango service bulletin for this exact problem of AC freezing.

I came across this bulletin has anyone done this and what wire and where is it located to add the 470 ohm resistor?


This is for a 2005 durango should work for the ram just need to find correct wire
24-004-10 -2-
PARTS REQUIRED:
Qty. Part No. Description

1 68064996AA Kit, Resistor
Kit includes; 1 470 ohm resistor, 2 wire shrink wraps and
2 splice crimps.


REPAIR PROCEDURE:
1. Remove and disconnect the ATC or MTC control head. Follow the detailed service procedures
available in DealerCONNECT/TechCONNECT, Refer To Group 24 - Heating & Air Conditioning > Controls,
Front> Controls, A/C & Heater Removal Procedures.
2. Using the wiring diagrams available in DealerCONNECT/TechCONNECT locate the evaporator
temperature sensor signal wire. Cavity 10 of the C2 black 12 - way connector for ATC systems.
Cavity 2 of 20 - way black C1 connector for MTC systems.
3. Measure 76mm (3 inches) down from end of ATC/MTC connector and cut the evaporator temperature
sensor signal wire.
4. Using the 2 splice crimps and 2 wire shrink wraps from resistor kit p/n 68064996AA, splice in
the 470 ohm resistor. Follow the detailed wiring procedures available in DealerCONNECT/TechCONNECT,
Refer To the Wiring Tab > 8W-01 - Wiring Diagram Information > Wire > Standard Procedure.

NOTE: Be sure to use the splice crimps and shrink wrap on wires and resistor.

5. Install the ATC or MTC control head. Follow the detailed service procedures available in
DealerCONNECT/TechCONNECT, Refer To Group 24 - Heating & Air Conditioning
> Controls, Front> Controls, A/C & Heater Installation Procedures.
6. Using the wiTECH™ or StarSCAN® erase all DTC.

POLICY:
Reimbursable within the provisions of the warranty.

TIME ALLOWANCE:



Labor Operation No: Description
Amount

24-35-51-90 Kit, resistor install. (B)
0.4 Hrs.

Good luck

 

Reporting back ... turns out you guys were right: low on refrigerant. I recharged it, and it's no longer icing up (and working properly).

Thank you all for the detailed suggestions. Motor on!

v