Windshield has a hazy film

Hi and thanks for using 2CarPros.

It sounds like you have a heater core issue. Is the coolant level dropping or is the passenger side floor wet? Do you notice a sweet smell in the vehicle such as coolant?

What happens is the core will leak, create steam composed of coolant, and it will fog the windshield. It isn't real easy to keep clean.

If you determine the heater core is the problem, and based on your description it is, here is a link that shows in general how one is replaced. Note: If you are only getting the typical fog on the windshield, make sure you have the system set on fresh air. That will help.

https://www.2carpros.com/articles/replace-heater-core

Here is a test for the heater core which may require removal. Pictures 1 and 2 correlate with these directions.
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Heater Core - Pressure Test
Use the Radiator/Heater Core Pressure Tester to carry out the pressure test.

1. NOTE: Due to space limitations, a bench test may be necessary for pressure testing.

Clamp off the heater hoses.

2. Disconnect the heater water hoses from the heater core.
3. Install a short piece of heater water hose, approximately 101 mm (4 inches) long on each heater core tube.

Picture 1

4. Fill the heater core and heater water hoses with water and install Plug BT-7422-B and Adapter BT-7422-A from the Radiator/Heater Core Pressure Tester in the heater water hose ends. Secure the heater water hoses, plug and adapter with hose clamps.
5. Attach the pump and gauge assembly from the Radiator/Heater Core Pressure Tester to the adapter.
6. Close the bleed valve at the base of the gauge. Pump 138 kPa (20 psi) of air pressure into the heater core.
7. Observe the pressure gauge for a minimum of 3 minutes.
8. If the pressure drops, check the heater water hose connections to the core tubes for leaks. If the heater water hoses do not leak, remove the heater core from the vehicle and carry out the bench test.

Heater Core - Bench Test
1. Remove the heater core from the vehicle.
2. Drain all of the coolant from the heater core.
3. Connect the 101 mm (4 in) test heater water hoses with plug and adapter to the core tubes. Then connect the Radiator/Heater Core Pressure Tester to the adapter.
4. Apply 138 kPa (20 psi) of air pressure to the heater core. Submerge the heater core in water.

Picture 2

5. If a leak is observed, install a new heater core.

Here are the directions for replacing the heater core. The attached pictures correlate with these directions. Note: if the heater core needs replaced, the AC system will need evacuated and recharged when the work is done. See directions.

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HEATER CORE AND EVAPORATOR CORE HOUSING

Picture 3

Picture 4

Removal and Installation

NOTE:
- The heater core and evaporator core are not individually serviced. They are serviced only with the heater core and evaporator core housing.

- If a heater core leak is suspected, the heater core must be leak tested before it is removed from the vehicle. See: Heating and Air Conditioning > Component Tests and General Diagnostics
- Installation of a new suction accumulator is not required when repairing the air conditioning system except when there is physical evidence of contamination from a failed A/C compressor or damage to the suction accumulator. See: Accumulator HVAC > Service and Repair

All vehicles
1. Recover the refrigerant.

2. Drain the engine coolant. See: Cooling System > Service and Repair
3. Remove the instrument panel.

5.4L (4V) vehicles

4. Remove the supercharger

Picture 5

5. Disconnect the heater hose fittings at the rear of the RH cylinder head and position the heater hoses aside.

All vehicles
5. Disconnect the heater core inlet and outlet hoses at the heater core.
6. Remove the 2 evaporator fitting nuts and disconnect the evaporator core fitting.
- Discard the O-ring seals.
- To install, tighten to 8 Nm (71 lb-in).

7. Remove the 2 exterior heater core and evaporator core housing nuts at the dash panel.
- To install, tighten to 7 Nm (62 lb-in).

8. Detach the antenna cable from the heater core and evaporator core housing.
9. Remove the interior heater core and evaporator core housing nut.
- To install, tighten to 5 Nm (44 lb-in).

10. Remove the heater core and evaporator core housing.
11. To install, reverse the removal procedure.
- Install new O-ring seals.
- Lubricate the refrigerant system with the correct amount of clean PAG oil.

12. Fill the engine cooling system. See: Cooling System > Service and Repair
13. Evacuate, leak test and charge the refrigerant system.

Let me know if this helps or if you have other questions. Note: If the fog on the windshield seems slippery or slimy, either the core is bad or you have a hose leaking to the core.

Take care,
Joe

It could cause an issue on all windows that receive air flow from the system. Is there any smell associated with it? Do you notice any steam from the defroster? Also, check the coolant level under the hood to see if it has lost any.

Yep. It really sounds like the heater core. The waxy substance is residue from coolant steam. And the smell, most likely it is coolant. You are losing coolant, but don't see a leak outside because it's leaking under the dash. If you wait long enough, I bet the top of the carpet starts getting wet with coolant.