servo turned to max but heater does not work ?

Most heater systems are operated by engine vacuum. This vacuum is used to actuate servos to move the temperature adjustment doors inside the heater plenum. If engine vacuum is not present the heater will not operate properly. To test for this condition remove the vacuum feed line from one of the vacuum servos. With the vacuum feed line removed insert a vacuum test gauge. If no vacuum is present, open the hood and inspect all small vacuum lines from the engine to the firewall and repair as needed. If a hissing noise is present under the dash when the engine is running a vacuum leak exists and must be repaired to restore heater function.

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Another possibility can be low coolant.Check the coolant level.If its low, get the coolant refilled.

Remove the reservoir cap and add coolant to the Full-Cold line, if a very short time after you refill the coolant reservoir the coolant level is low, there is a leak in your car’s cooling system.

Engine coolant is used to heat the heater core and if the vehicle is low on coolant the heater core will stop working. The heater cannot produce heat due to the lack of heat from the engine coolant. Even if the engine is not over heating the coolant level can still be low.

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Another possibility can be faulty heater control valve:---

The heater control valve is used to shut off hot coolant from entering the core when the heater is in the off position. A heater control valve can be actuated by either a vacuum line or a cable from the vacuum heater control valve to the heater core. This hose should be warm; if not the heater control valve is stuck and needs to be replaced.

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Another possibility can be faulty heater core:---

Start by checking the coolant. As we already said coolant is what warms the heater core. So if the coolant is low, there may not be a sufficient amount of warmth to transfer heat to the air in the passenger compartment.Once the coolant is full, feel the heater hoses that go through the firewall. With the engine at normal operating temperature, BOTH of the heater hoses should be hot to the touch. If only one is hot, this indicates there is is a blockage in the heater core or there is air trapped in the heater core.One hose hot, one cold, points to a plugged heater core.If this is the case,try flushing the heater core.There are no valves in the heater core; it is free flow at all times.Also check the head gasket. just because there is no water coming out of the exhaust dos,nt mean the head gasket is ok.How much pressure is in the system?.Are the water hoses very hard when the engine is hot?.......air in the system will stop the heater from working.------------Also try this procedure to clean the block in the heater core.If there is any:--- Put in a cleaner, Prestone, and drive car few hours.Then check if nNo success. Then get cleaner made by Gunk.You can get it from any local auto part store. Drain heater core, leave both heater hoses attached to the heater. Remove other ends of both hoses from the tubes on the thermostat housing and raise these ends above the heater core. Pour Gunk cleaner in one hose and add water until cleaner started to come out other hose. Leave this sit 4 hours and back flush heater core in both directions. Next back-flush block and radiator in both directions. Water should come out of tube on the thermostat housing that has a hose attached to the outlet of the heater core.If not coming then Flush water directly into this tube about 15 to 20 times and you will hear a thud of water coming out.. Back flush block and radiator again and this time water should out the tube previously blocked. But if problem is same and no difference.Then is faulty heater core.Its causing the problem and it needs to be replaced.Also check the radiator,if its blocked then get the radiator back flushed too.

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To remove heater core out.Follow this procedure:----

1. Disconnect the negative battery cable.

Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

1. Drain the engine coolant into a suitable container.

2. Disconnect the heater hoses at the firewall in the engine compartment.

3. Remove the instrument panel assembly.

4. Remove the air inlet assembly as follows:

   1. If necessary, tag and disconnect the vacuum connectors.

   2. Remove the air inlet studs, the inlet assembly and if necessary the gasket.

5. Tag and disconnect all necessary vacuum lines.

6. From inside the engine compartment, remove the heater assembly studs.

7. Remove the blower motor resistor as follows:

   1. Unplug the resistor electrical connection.

   2. Unfasten the screws and remove the resistor.

8. Once the resistor is removed it will uncover a stud inside the heater core housing. Remove this stud.

9. Remove the rear case screws, the heater assembly and the seals.

To install:

1. Install the seals, the heater assembly and the rear case screws.

2. Install the stud inside the heater core housing and tighten to 17 inch lbs. (1.9 Nm).

3. Install the blower motor resistor as follows:

   1. Place the resistor in position and tighten the screws to 17 inch lbs. (1.9 Nm).

   2. Attach the electrical connector to the resistor.

4. Working inside the engine compartment, install the heater assembly studs. Tighten the studs to 17 inch lbs. (1.9 Nm).

5. Attach and disconnected vacuum lines.

6. Install the air inlet assembly as follows:

   1. If removed, install the inlet assembly gasket.

   2. Install the inlet assembly and the studs. Tighten the studs to 40 inch lbs. (4.5 Nm).

   3. Attach all unplugged vacuum connectors.

7. Install the instrument panel assembly.

8. Attach the heater hoses to the core tubes at the engine compartment firewall.

9. Refill the engine cooling system.

10. Connect the negative battery cable, start the vehicle and check for coolant leaks.

utility models

Be sure to consult the laws in your area before servicing the air conditioning system. In most areas, it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician. Also, it is quite likely that you will not be able to purchase refrigerant without proof of certification.

Discharging, evacuating and charging the air conditioning system must be performed by a properly trained and certified mechanic in a facility equipped with refrigerant recovery/recycling equipment that meets SAE standards for the type of system to be serviced. If you don't have access to the necessary equipment, we recommend that you take your vehicle to a reputable service station to have the work done. If you still wish to perform repairs on the vehicle, have them discharge the system, then take your vehicle home and perform the necessary work. When you are finished, return the vehicle to the station for evacuation and charging. Just be sure to cap ALL A/C system fittings immediately after opening them and keep them protected until the system is recharged.

1. Have the A/C system evacuated by a certified technician using approved equipment.

2. Disconnect the negative battery cable.

3. Remove the instrument panel.

4. Remove the cowls, unplug the washer lines from the hood.

5. Unplug the underhood lamp electrical, if equipped, then remove the hood.

6. Remove the antenna and the PCM.

CAUTION Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

Drain coolant into a suitable container and remove the coolant recovery reservoir.

1. Disconnect the coolant hoses from the heater core at the firewall in the engine compartment.

2. Remove the right headlamp assembly. Tag and unplug all necessary electrical connections.

3. Remove right side fender.

4. Remove the battery, battery tray, and the wheel house panel.

5. Disconnect the A/C lines from the evaporator.

6. Unfasten the heater box shield retainers and remove the shield.

7. Unfasten the heater core mounting bolts from the engine compartment and remove the heater core fasteners from inside the vehicle.

8. With the aid of an assistant inside the vehicle, gently pry back on the heater box while removing the evaporator housing assembly to ensure clearance of the stud.

9. Remove the heater case, core and the seals.

To install:

1. Install the seals, core and case.

2. With the aid of an assistant inside the vehicle, pull forward on the heater box to make sure the evaporator core is in the correct position.

3. Install the heater case fasteners. Tighten the bolt/screw to 40 inch lbs. (4.5 Nm) and the stud to 40 inch lbs. (4.5 Nm).

4. Install the evaporator housing mounting bolts and tighten the bolt/screw to 40 inch lbs. (4.5 Nm).

5. Install the heater box shield and tighten the retainers to 19 inch lbs. (2.2 Nm).

6. Attach the A/C lines to the evaporator.

7. Install the wheel house panel, the battery tray and the battery. Do not connect the battery cables just yet.

8. Install the outer fender and attach all electrical connections that were disconnected.

9. Install the right headlamp assembly.

10. Attach the heater hoses to the heater core and install the coolant recovery reservoir.

11. Fill the cooling system.

12. Install the PCM and the antenna.

13. Install the hood, attach the hood lamp electrical connection and the washer lines. Install the cowls.

14. Install the instrument panel.

15. Connect the batter cables, start the vehicle and check for leaks.

16. Instrument panel removal.

    1997-99 Models

    CAUTION<>when performing service around the air bag system components or wiring, the air bag system MUST be disabled. Failure to do so could result in possible air bag deployment, personal injury or unneeded air bag system repairs.

    1. Disconnect the negative battery cable.

    2. Disable the air bag system.

    3. Set the parking brake and block the wheels.

    4. Disconnect the parking brake release cable from the parking brake lever.

    5. Unfasten the screws that retain the Data Link Connector (DLC) instrument panel left side sound insulator. Feed the DLC through the hole in the sound insulator.

    6. Unfasten the right side sound insulator panel screws and remove the panel.

    7. Unfasten the screws that attach the instrument panel left side sound insulator to the knee bolster and cowl panel.

    8. Unfasten the nut that attaches the left side sound insulator to the accelerator pedal bracket.

    9. Unplug the remote control door lock receiver module electrical connector.

    10. Remove the door lock receiver module from the left side sound insulator. Remove the left side sound insulator.

    11. Unfasten the screws that attach the instrument panel center sound insulator to the knee bolster, instrument panel, heater assembly and floor duct.

    12. Remove the center sound insulator.

    13. Unfasten the screws that attach the courtesy lamp to the knee bolster.

    14. Unfasten the screws that attach the knee bolster to the instrument panel.

    15. Disconnect the lap cooler duct from the knee bolster.

    16. Unplug the lighter electrical connection and remove the knee bolster.

    17. Unfasten the steering column-to-instrument panel nuts and lower the column.

    18. Unfasten the screws that attach the instrument panel accessory trim plate to the instrument panel.

    19. Remove the trim plate and unplug all necessary electrical connection.

    20. Remove the heater and/or A/C control assembly.

    21. Remove the radio and the storage compartment assembly (if equipped).

    22. If necessary, remove the instrument cluster.

    23. Unfasten the left and right instrument panel pivot bolts and the panel lower support bolt.

    24. Unfasten the speaker grilles retaining screws and remove the speaker grilles.

    25. Remove the windshield defroster grille using a flat-bladed prytool. Start at one end of the grille and work your way down the grille.

    26. Unfasten the four instrument panel upper support screws.

    27. Tag and unplug all necessary electrical connections.

    28. Remove the instrument panel from the vehicle.

    To install:

    1. Rest the instrument panel on the lower pivot studs.

    2. Attach the electrical connections.

    3. Install but do not tighten the four upper instrument panel support screws.

    4. Install the left and right panel pivot bolts. Tighten the bolts to 102 inch lbs. (11.5 Nm).

    5. Install the panel lower support bolt. Tighten the bolt to 102 inch lbs. (11.5 Nm).

    6. Tighten the upper support screws to 17 inch lbs. (1.9 Nm).

    7. Install the windshield defroster grille and the speaker grilles.

    8. Install the radio and storage compartment assembly (if equipped).

    9. If removed, install the instrument cluster.

    10. Install the heater and/or A/C control assembly.

    11. attach the electrical connections to the instrument panel accessory trim plate.

    12. Place the trim plate in position and install its retaining screws. Tighten the screws to 17 inch lbs. (1.9 Nm).

    13. Place the steering column into position and install its retaining nuts. Tighten the nuts to 22 ft. lbs. (30 Nm).

    14. Attach the lighter electrical connection and the lap cooler duct to the knee bolster.

    15. Place the knee bolster into position and install its retaining screws. Tighten the Torx® head screws to 80 inch lbs. (9 Nm) and the hex head screws to 17 inch lbs. (1.9 Nm).

    16. Place the courtesy lamp in position and install its screws. Tighten the screws to 17 inch lbs. (1.9 Nm).

    17. Place the instrument panel center sound insulator in position. Install the screws that attach the center sound insulator to the knee bolster, instrument panel and the floor duct. Tighten the screws to 17 inch lbs. (1.9 Nm).

    18. Install the screw that attaches the center sound insulator to the heater assembly. Tighten the screw to 13 inch lbs. (1.5 Nm).

    19. Install the remote control door lock receiver module to the instrument panel left side sound insulator.

    20. Attach the door lock receiver electrical connection.

    21. Install the nut that attaches the left side sound insulator to the accelerator pedal bracket. Tighten the nut to 35 inch lbs. (4 Nm).

    22. Install the screw that attaches the left side sound insulator to cowl panel. Tighten the screw to 13 inch lbs. (1.5 Nm).

    23. Install the screws that attach the left side sound insulator to knee bolster. Tighten the screw to 17 inch lbs. (1.9 Nm).

    24. Feed the DLC through the hole in the sound insulator, place the DLC in position and install its retaining screws. Tighten the screws to 21 inch lbs. (2.4 Nm).

    25. Install the right side sound insulator and tighten the screws

    26. Connect the parking brake release cable to the lever.

    27. Enable the air bag system.

    28. Connect the negative battery cable.

        
        

        
        

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