Having trouble getting heat on drivers' side

Hi,

The easiest way to determine if the heater core is plugged is this. Start the engine and turn on the heater. Allow the engine to reach operating temperature and then feel both heater hoses. One will be hot and the other a slight bit cooler, but still hot. If they are both hot, the core isn't the issue.

Since you are getting heat on one side, I feel the problem has nothing to do with the heater core. There is only one, so you wouldn't get any heat if it were plugged.

Next, the idea that airflow is from the floor in the defrost position is an issue with a mode door. That is what determines the airflow direction. Is that what is happening? The temperature being off is the blend actuator.

Take a look at the pic below and let me know if the blend door actuator I highlighted has been checked. Also, I highlighted the two mode door actuators. If the airflow directions are incorrect, we need to inspect them as well.

Let me know.

Take care,

Joe

See pic below.

Hi,

If you allow the engine to run at operating temperature, the heat will transfer into both heater core hoses. However, if the core is plugged, one will be much hotter.

The idea that you get heat in the vehicle, the core doesn't sound plugged.

I need to confirm something. Does this truck have a dual or single-zone system? If you look at the pic below, you'll see the two different actuators. One is for the left and the other is for the right.

Try this. Disconnect the mode door lever and move it manually to see if the door feels to be moving and if it changes the temperature entering the vehicle.

Let me know.

Joe

This truck like many newer vehicles uses a parallel flow heater core. In those flushing is almost impossible because of the way the coolant flows across them. Think of it like two roads that run side by side. The core then has say 60 cross roads that join those two main roads. The problem is that it only takes about 5 of those roads to handle all of the coolant flow across the core, So if the rest of the core is plugged the hoses would still get hot and flushing would show nothing wrong. However, a common symptom of a plugged core in a dual zone system is to lose heat on one side of the vehicle because they more or less split the core so one end feeds each side of the vehicle. In this case the driver's side is also the end of the heater core that doesn't have the hoses attached to it and it has plugged up. The coolant Chrysler used in those days had a bad habit of breaking down in about 2 years and would develop these strands of goo in it over time, those strands would build up in areas of lower flow, like the far end of the heater core and then it would solidify there. The end result would be the core gradually stops working as it plugs. The reason why the air is colder on defrost is because like most cars built after the mid 90's the defrost system also cycles the A/C on to help dry out the air coming through the system by acting as a dehumidifier. That keeps you from suddenly having condensation or even ice forming on the interior of the glass if the conditions are right. So in your case the heater core is partly plugged, on defrost the air comes into the HVAC case, through the colder A/C core where it cools way down and should condense out any moisture, then through the heater core to heat it up to warm the cabin or defrost the glass. With the core partially blocked the colder air doesn't warm up, instead it stays colder than the outside air because of the way the system works.
This didn't happen a lot in older vehicles because they used a serpentine coolant flow through the core. On them the coolant went into one half of the core and flowed to the opposite end, then transferred across in that ends tank to return up the other side of the core. So, in those it took coolant flowing through the core to get both hoses hot. This is why you were told it is no longer a valid test. The attached images show the two types of heater core. The one in your truck is the second one with the large yellow area showing the blocked side, the upper section is still free flowing, so you have heat on one side only.
I have seen reverse flushing with an air boosted flush gun work on them but it's not a sure thing.
Instead, the repair is to replace the heater core.
This is similar as you have to remove the dash and HVAC case to remove the heater core.
https://www.2carpros.com/articles/replace-heater-core

1. Disconnect and isolate the battery negative cable.
2. Drain the engine cooling system.
3. Recover the refrigerant from the refrigerant system.
4. Disconnect the liquid refrigerant line fitting from the evaporator inlet tube. Discard the O-ring seal and install plugs in, or tape over the opened liquid refrigerant line fitting and evaporator inlet tube.
5. Remove the accumulator. Discard the O-ring seals and install plugs in, or tape over the opened refrigerant line fittings and evaporator outlet tube.
6. Disconnect the heater hoses from the heater core tubes. Install plugs in, or tape over the opened heater core tubes.
7. Remove the powertrain control module (PCM) from the engine compartment to gain access to the HVAC housing retaining nuts.
8. Remove the two nuts from the HVAC housing mounting studs in the engine compartment.
9. Remove the instrument panel from the vehicle.
10. Remove the bolt that secures the HVAC housing to the floor bracket located in the center of the vehicle.
11. Remove the two nuts from the HVAC housing mounting studs in the passenger compartment.
12. Remove the HVAC housing from inside the vehicle. Take care not to allow any remaining coolant to drain onto the vehicle's interior.

If possible use a flush tool. They use shop air regulated down along with the water pressure, so it really stirs up the crud in the core. Reverse flush it then swap back and forth a few times, you may get enough out to make it work. The attached are some of the common ones, they are not hard to make using a garden hose spray nozzle and a couple fittings or other pieces. I have used my OTC unit for a lot of years. About 35 PSI air works as a start unless you have high water pressure. Then you want to regulate them both to prevent damaging the core.

Hi,

Thanks for the update. As far as the cold air on the driver's side floor with the defroster on, have you checked the mode door actuator? That is what is responsible for airflow direction. Something may not be closing fully or loose.

This vehicle has two mode actuators. One is for defrosting to the floor, and the other is from panel to floor.

I attached a pic of the mode door actuator that controls the defroster to floor operation. Make sure it is tight. If it is, remove it and inspect for anything that could be preventing the actuator from fully moving the door into the correct positions.

Let me know what you find.

Take care,

Joe

See pic below.