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Is it necessary to evacuate the freon from the car's air-conditioning system prior to removing the heater plenum and replacing the heater core?

Dealer had to replace the heater plenum because of a broken blend door. The service manager said that it would not be necessary to remove the freon.

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NO they do not interconnect plumbing .

Posted on Apr 20, 2015

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2 Answers

Why must i discharge the air conditioning refridgerant prior to removal of the heater core on a 2003 c230 mercedes 1.8l coupe.


The reason in why you must evacuate the a/c system with an a/c machine before you can remove the heater core is because the evaporator is located inside of the heater core box assembly. So before the heater core box assembly can be removed the a/c system must be evacuated then you can disconnect the a/c lines that go through the firewall to the evaporator.

Jul 01, 2015 | 2004 Mercedes-Benz C230 Kompressor

1 Answer

Picture diagram or written detailed instructions on how to replace heater core in a 92 ford taurus?


I have done this in an '86 Sable which is very similar. It is a very long process (an 8-10 hour job as listed by Ford Service).

Basically, you are going to have to drain the coolant, evacuate the air conditioning system of refrigerant, disconnect the battery, disable the airbag system (if applicable), remove the panel under the steering wheel, drop the steering column, remove the dashboard, cut the A/C plenum and remove the A/C evaporator, remove the heater core.

This is a very big job for a do-it-yourselfer, but it has been done. I highly recommend buying a Chilton manual or borrowing from a library. Some libraries have the Chilton manuals available for viewing online.

Good luck from Detroit, MI

P.S.: When I did all that on my Sable, it turned out that the heater core wasn't leaking... the hose clamps were loose and a hose was shooting coolant through the firewall into the heater plenum! D'oh!

Oct 25, 2011 | 1992 Ford Taurus

1 Answer

How to remove heater core on a 1994 isuzu pickup


Removal & Installation

Fig. 1: When installing the new heater core take great care not to bend or damage the fins or tubing
[IMG]http://i665.photobucket.com/albums/vv17/technovative/Isuzu-Pickup-Heater-Core.gif[/IMG]
Click here if image doesn't display.
  1. Disconnect the negative battery cable.
  2. Drain the engine coolant into a suitable container. CAUTION
    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 quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.
  3. Disconnect the heater hoses. Be careful not to damage the core by pulling on the hose to remove. Cut the hoses if they will not come off easily.
  4. Remove the instrument panel.
  5. Disconnect the resistor assembly.
  6. If possible, disconnect and move the duct (non air conditioning) or the evaporator housing (air conditioning) to the right to gain clearance for the heater unit. If equipped with air conditioning, do not disconnect air conditioning system until absolutely necessary. Refer to Section 1 for discharging, evacuating and recharging the system.
  7. Remove the instrument panel stay and heater unit.
  8. Disassemble the heater unit by removing the duct, mode control case, core assembly and heater core. To install:
  9. Assemble the heater unit by installing the duct, mode control case, core assembly and heater core.
  10. Install the heater unit and instrument panel stay.
  11. Connect the duct (non air conditioning) or the evaporator housing (air conditioning) to the heater unit. Evacuate and recharge the air conditioning system if the system was discharged to remove the evaporator assembly.
  12. Connect the resistor assembly.
  13. Install the instrument panel as outlined in this section.
  14. Connect the heater hoses. Be careful not to damage the core by pulling on the hose.
  15. Refill the engine coolant into a suitable container.
  16. Connect the negative battery cable and check for leaks.

Jan 30, 2011 | 1994 Isuzu Pickup

1 Answer

Replacing the heater core, how do i do it


The dash panel has to be removed along with the steering wheel and steering column to access the plenum box. The plenum box then has to be removed to get to the heater core. This requires evacuating the AC system, draining the radiator, disconnecting all lines and removing the box. Replacing the heater core is simple when you get to this point.

If the problem is lack of heat(not a physical leak), the problem is more likely with the blend doors on the explorer. This is a very common fail mode.

Jan 20, 2011 | 1996 Ford Explorer

1 Answer

Need to replace heater core? how do i remove old one and replace new one?


Here are the instructions with a diagram. If you need to enlarge the diagram save it to your picture files and then enlarge it there.

1. Disconnect battery ground cable, then drain cooling system. See: Engine, Cooling and Exhaust\Cooling System\Service and Repair

2. Disconnect heater hoses from heater core. Plug heater hoses and core fittings to prevent coolant spillage.


3. Remove bolt located below windshield wiper motor, attaching left end of plenum to dash panel.


4. Remove nut attaching upper left corner of evaporator or heater case to dash panel.
5. Disconnect vacuum control system supply hose from vacuum source, then push grommet and hose into passenger compartment.

6. Remove all instrument panel retaining screws and pull instrument panel back as far as possible without disconnecting any wire harnesses.
7. Loosen right door sill plate and remove side cowl trim panel.

8. Disengage temperature control cable housing from bracket on top of plenum. Disconnect cable from temperature blend door crank arm.

9. On models w/Automatic Temperature Control (ATC) , remove cross body brace and disconnect wiring harness from temperature blend door actuator and disconnect ATC sensor tube from evaporator case connector.
10. Disconnect vacuum harness at vacuum connector near floor air distribution duct.

11. Disconnect white vacuum hose from outside recirculating air door vacuum motor.
12. Remove two hush panels.

13. Remove one plastic push fastener retaining floor air distribution duct to left end of plenum. Remove left screw and loosen right screw on rear face of plenum. Remove floor air distribution duct.

14. Remove two screws from rear side of floor air distribution duct to plenum. To remove right screw, it may be necessary to remove the two screws attaching lower panel door vacuum motor to mounting bracket.

15. Remove push fastener attaching floor air distribution duct to left end of plenum, then remove floor air distribution duct.
16. Remove two nuts located along lower flange of plenum.
17. Carefully move plenum rearward, so that heater core tubes and plenum case upper stud clear openings in dash panel, then remove plenum from vehicle by rotating upper portion of the plenum forward, down and out from under instrument panel. It may be necessary to carefully pull lower edge of instrument panel rearward while plenum is being removed from behind instrument panel.
18. Remove retaining screws from heater core cover, then the cover from plenum assembly.

19. Remove retaining screw from heater core inlet and outlet tube bracket.


Heater core removal and installation diagram.




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20. Pull heater core and seal assembly from plenum assembly.
21. Reverse procedure to install.

Jan 06, 2011 | 1993 Mercury Grand Marquis

1 Answer

Need to find out how to replace a heater core on a 1999 chevy c 1500 pic-up.


You might not want to try this if you are not mechanically inclined.Plus you also nee to partially remove the instrument panel and the steering wheel and you will also need to evacuate the freon from the a/c system.After the instrument carrier is out of the way you have to remove the hvac plenum and disassemble it to remove the heater core.About a seven hour job for an experienced technician.Are you sure you want to tackle this?

Nov 06, 2010 | 1999 Chevrolet Silverado 1500

3 Answers

Looking to replace heater core


Cherokee, Grand Cherokee, 1999-2005

Removal & Installation
  1. Disconnect and remove the negative battery.
    CAUTION After disconnecting the negative battery cable, wait 2 minutes for the driver-s/passenger-s air bag system capacitor to discharge before attempting to do any work around the steering column or instrument.
  2. Drain the cooling system into a clean container for reuse.
  3. Remove the instrument panel by performing the following procedure:
    1. Turn the steering wheel in the straight-ahead position.
    2. Remove the knee blocker from the instrument panel.
    3. Remove the steering column; do not remove the air bag module, the steering wheel or switches from the steering column.
    4. From under the driver-s side of the instrument panel, disconnect the following items:

      Instrument panel wiring harness connector from the 100-way wiring harness connector at the left side of the inner panel. Side window demister hose at the heater/air conditioning housing demister/defroster duct on the driver-s side.
    5. Remove the glove box.
    6. Reaching through the glove box opening, disconnect the following items:

      Two halves of the heater/air conditioning system vacuum harness connector. Instrument panel wiring harness connector from the heater/air conditioning system wiring harness connector. Instrument panel wiring harness connector from the passenger-s side air bag module wiring harness connector. Side window demister hose at the heater/air conditioning housing demister/defroster duct (passenger-s side). Two halves of the radio antenna coaxial cable connector. Two instrument panel wiring harness connectors from the passenger air bag ON/OFF switch wiring harness connector. Passenger-s side air bag ON/OFF switch wiring harness from the retainer clip on the plenum bracket that supports the heater/air conditioning housing just inboard of the fuse block module. Two lower passenger-s side air bag module bracket-to-dash panel nuts.
    7. Remove the upper cover from the instrument panel.
    8. Remove the 3 instrument panel-to-door hinge pillar screws.
    9. Remove the 4 upper instrument panel-to-dash nuts.
    10. Using an assistant, remove the instrument panel from the vehicle.
  4. If equipped with air conditioning, discharge and recover the air conditioning system refrigerant.
  5. Disconnect the refrigerant lines from the evaporator. Plug the refrigerant openings to prevent evaporation.
  6. Disconnect the heater hoses from the heater core tubes.
  7. Disconnect the heater/air conditioning system vacuum supply line connector from the T-fitting near the heater core tubes.
  8. In the engine compartment, remove the 5 heater/air conditioning housing-to-chassis nuts. If necessary, loosen the battery hold-downs and reposition the battery for access.
  9. Remove the cowl plenum drain tube from the heater/air conditioning housing stud; it-s located behind the cylinder head on the cowl.
  10. From the bottom of the heater/air conditioning housing, remove the floor duct.
  11. On the passenger side, remove the heater/air conditioning housing-to-plenum bracket screw.
  12. Pull the heater/air conditioning housing down far enough to clear the defrost/demist and fresh air ducts, then, rearward far enough to clear the mounting studs and the evaporator drain tube to clear the dash panel holes.
  13. Remove the heater/air conditioning housing assembly from the vehicle.
  14. Remove the heater/air conditioning housing upper case.
  15. Lift the heater core from the lower half of the heater/air conditioning housing.
To install:
  1. Assemble the heater core into the lower half of the heater/air conditioning housing.
  2. Install the heater/air conditioning housing upper case.
  3. Install the heater/air conditioning housing assembly to the vehicle.
  4. On the passenger-s side, install the heater/air conditioning housing-to-plenum bracket screw.
  5. At the bottom of the heater/air conditioning housing, install the floor duct.
  6. Install the cowl plenum drain tube to the heater/air conditioning housing stud; it-s located behind the cylinder head on the cowl.
  7. In the engine compartment, install the 5 heater/air conditioning housing-to-chassis nuts.
  8. Connect the heater/air conditioning system vacuum supply line connector to the T-fitting near the heater core tubes.
  9. Connect the heater hoses to the heater core tubes.
  10. Connect the refrigerant lines to the evaporator.
  11. If equipped with air conditioning, evacuate and charge the air conditioning system refrigerant.
  12. Install the instrument panel by performing the following procedure:
    1. Using an assistant, install the instrument panel to the vehicle.
    2. Install the 4 upper instrument panel-to-dash nuts.
    3. Install the 3 instrument panel-to-door hinge pillar screws.
    4. Install the upper cover to the instrument panel.
    5. Reaching through the glove box opening, connect the following items.

      Two lower passenger-s side air bag module bracket-to-dash panel nuts. Passenger-s side air bag ON/OFF switch wiring harness to the retainer clip on the plenum bracket that supports the heater/air conditioning housing just inboard of the fuse block module. Two instrument panel wiring harness connectors to the passenger air bag ON/OFF switch wiring harness connector. Two halves of the radio antenna coaxial cable connector. Side window demister hose at the heater/air conditioning housing demister/defroster duct (passenger-s side). Instrument panel wiring harness connector to the passenger-s side air bag module wiring harness connector. Instrument panel wiring harness connector to the heater/air conditioning system wiring harness connector. Two halves of the heater/air conditioning system vacuum harness connector.
    6. Install the glove box.
    7. Under the driver-s side of the instrument panel, connect the following items:

      Side window demister hose at the heater/air conditioning housing demister/defroster duct on the driver-s side. Instrument panel wiring harness connector to the 100-way wiring harness connector at the left side of the inner panel.
    8. Install the steering column.
    9. Install the knee blocker to the instrument panel.

  13. Connect and remove the negative battery.
  14. Refill the cooling system.
  15. Run the engine to normal operating temperatures; then, check the climate control operation and check for leaks.

Hope helps (remember rated this).

Jun 25, 2010 | 2001 Jeep Grand Cherokee

1 Answer

Hearter core removal


  1. Disconnect the negative (-) battery cable.
  2. Drain the engine coolant into a suitable container.


CAUTION 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 quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.
  1. Disconnect the heater hoses. Be careful not to damage the core by pulling on the hose to remove. Cut the hoses if they will not come off easily.
  2. Remove the instrument panel.
  3. Disconnect the resistor assembly.
  4. If possible, disconnect and move the duct (non air conditioning) or the evaporator housing (air conditioning) to the right to gain clearance for the heater unit. If equipped with air conditioning, do not disconnect air conditioning system until absolutely necessary. Refer to for discharging, evacuating and recharging the system.
  5. Remove the instrument panel stay and heater unit.
  6. Disassemble the heater unit by removing the duct, mode control case, core assembly and heater core.

To install:
  1. Assemble the heater unit by installing the duct, mode control case, core assembly and heater core.
  2. Install the heater unit and instrument panel stay.
  3. Connect the duct (non air conditioning) or the evaporator housing (air conditioning) to the heater unit. Evacuate and recharge the air conditioning system if the system was discharged to remove the evaporator assembly.
  4. Connect the resistor assembly.
  5. Install the instrument panel as outlined in this section.
  6. Connect the heater hoses. Be careful not to damage the core by pulling on the hose.
  7. Refill the engine coolant into a suitable container.
  8. Connect the negative (-) battery cable and check for leaks.

Jan 20, 2010 | 1996 Isuzu Trooper

1 Answer

How do I change the heater core in my 1984 grand marquis? I dont have a manual


you have to remove the plenum case behind the dash. I will provide 94 gr marquis. don't have 84.



---------------------------------------------------------------------------------------
Section 12-03A: Air Conditioning System—Manual A/C-Heater 1994 Crown Victoria/Grand Marquis. Workshop Manual
REMOVAL AND INSTALLATION Heater Core Removal
  1. Remove the heater air plenum chamber assembly as outlined.
  2. Heater Air Plenum Chamber Removal
    1. Disconnect battery ground cable .
    1. Disconnect the heater water hoses from the heater core tubes. Plug the ends of the heater water hoses to prevent coolant loss.
    1. Plug heater core tubes securely to prevent coolant leakage from heater core during heater air plenum chamber removal.
    1. Remove three nuts located below the windshield wiper motor (17508) retaining the LH end of the heater air plenum chamber to the dash panel .
    1. Remove one nut retaining the upper LH corner of the A/C evaporator core housing to the dash panel .
    1. Remove LH and RH lower instrument panel insulators.
    1. Disconnect two vacuum supply hoses from vacuum source. Push grommet and vacuum supply hose into passenger compartment.
    1. Remove all instrument panel retaining screws and pull the instrument panel back as far as possible without disconnecting any wire harnesses.
    1. Loosen the RH door sill plate and remove the RH side cowl trim panel.
    1. Remove cross body brace and disconnect wiring harness from A/C electronic door actuator motor (19E616) and disconnect the sensor tube from the evaporator case connector.
    1. Disconnect the vacuum jumper harness at the multiple vacuum connector near the heater outlet floor duct.
    1. Disconnect the white vacuum hose from the heater and A/C air inlet duct door vacuum control motor.
    1. Remove two hush panels.
    1. Remove one plastic push fastener retaining the heater outlet floor duct to the LH end of the heater air plenum chamber . Remove LH screw and loosen RH screw on the rear face of the heater air plenum chamber and remove the heater outlet floor duct .
    1. Remove two nuts from the two studs along the lower flange of the heater air plenum chamber .
    1. Carefully move heater air plenum chamber rearward to allow heater core tubes and the stud at the top of the heater air plenum chamber to clear holes in the dash panel. Remove heater air plenum chamber from vehicle by rotating the top of the heater air plenum chamber forward, down and out from under the instrument panel . Carefully pull lower edge of instrument panel rearward as necessary while rolling the heater air plenum chamber from behind the instrument panel .
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  1. Remove the four retaining screws from the heater core cover (18B300) and remove the heater core cover from the heater air plenum chamber assembly.

    Heater Core Removal


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    Item Part Number Description 1 390092-S2 Screw (2 Req'd) 2 18658 Heater Core Case Seal 3 18476 Heater Core 4 18570 Heater Dash Gasket 5 18471 Heater Air Plenum Chamber 6 18B300 Heater Core Cover
  1. Pull the heater core assembly from the heater air plenum chamber assembly.
Installation
  1. Carefully install heater air plenum chamber assembly into the heater air plenum chamber assembly. Visually check to ensure that core seal is properly positioned.
  1. Position the heater core cover and install the four retaining screws.
  1. Install the heater air plenum chamber assembly as outlined.

Feb 27, 2009 | 1984 Mercury Grand Marquis

1 Answer

Jeep grand cherokee 1999


check wjjeeps.com for information. Changing the heater core requires complete removal of the dash panel and plenum box. To do this you have to remove the steering wheel, steering column, evacuate and recharge the refrigerant system and drain the radiator. I would only consider changing the heater core if it is physically leaking into the passenger compartment. If the problem is heat transfer to the HVAC system only, the problem is more likely with the blend doors. Check heatertreater.net for pictures and diagnostic information.  http://www.wjjeeps.com/hvac_ip_remove.htm 

This website gives detailed instructions on how to remove the dash as part of getting to the heating/air conditioning system. 
Be aware that you should dedicate at least a whole weekend to this project minimally. 

Yes. Its a tough job. You have to remove the dash panel, including the steering wheel and steering column and then remove the plenum box which involve evacuating the refrigerant system and draining the radiator. Once you get the heater box out, replacing the heater core will take about 10min and then you have to put it all back together and recharge the AC and fill the radiator. 

If you are seeing leak problems with the system, you will have to go through this process. If the problem is lack of heat and/or AC control, the problem is more likely the blend door. This is a common fail on the Cherokee. You can get diagnostic information and an inexpensive fix on the HeaterTreater web site. Follow my user name to my Bio Page for a pointer or just search heatertreater on any search engine. ford4me 

Feb 09, 2009 | 1999 Jeep Grand Cherokee

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