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'00 300m - very little heat from heater

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Nov 22, 2015.

  1. MoPar~Man

    MoPar~Man Active Member

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    I noticed this last winter, and since we've had an abnormally cold day today I'm still seeing this. Temperature guage shows that engine is up to temperature but I'm getting little more than luke-warm heat from the vents. Outside air temp was about 25 f.

    Is there something in or under the dash that can cause this (a door, flap, link or solenoid) or could this be caused by the water pump (impeller has become disconnected with drive shaft) such that the impeller still turns, but not as fast as it should. ?
     
  2. floridaman2013

    floridaman2013 Active Member

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    Check temp of hoses in and out from heater core, feel by hand if you need. if one side a lot cooler, core might need flushing or back flush too. Always check your heater control doors for proper operation also, but see if both hoses are pretty hot first, as this is simple and doesn't cost any money.
     
  3. dana44

    Ad-Free Member

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    That, and check the fluid level at the radiator and don't believe the level at the overflow. Quite often there is enough fluid in the engine to not harm it, but the level in the radiator is low so no fluid in the heater core itself, thus cooler heater. When verifying the level, make sure the heater is turned on heat full blast so the fluid flows through and removes air from the heater core itself (it is, after all, a small radiator).
     
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  4. MoPar~Man

    MoPar~Man Active Member

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    Is the heater hose inlet/outlet accessible ("feelable") from under the dashboard?

    Is it true that if there is coolant at the level of the engine thermostat that there could be no coolant in the heater lines?

    I know that some cars have a vacuum-controlled valve in the engine compartment that allowed or prevented hot coolant from entering the heater core - does the 300m have such a valve?
     
  5. MoPar~Man

    MoPar~Man Active Member

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    I tried the 3-button ATC test (set temp for 75, press 3 buttons) and when the display stopped flashing and returned to normal mode - no codes were displayed. Nothing to indicate that the test had finished - it just returned to a normal-looking display. During the test I heard motors or doors opening and closing, the AC went on and then off, air blowing through different vents, etc. If this test accurately tests the blend door or gate, then I guess mine must be working.
     
  6. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    You can feel both heater hoses underhood while engine is warm to see if both are hot. They should be. If not, and engine temperature reads normal, heater core may be clogged.
     
  7. valiant67

    valiant67 ...

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    It was common in vehicles of that vintage for the heater cores to plug. I've never had an LH car but the Neons and Dakotas I've had benefited from a heater core flush.
     
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  8. ImperialCrown

    ImperialCrown Moderator
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    A reverse-flush may work if the core is restricted by soft debris. Hard deposits and corrosion may not remove with a flush.
    The reverse-flush flows the opposite direction of normal flow and might push out some restriction.
    Because of the expense and difficulty in replacing a heater core, I would try it first. A garden hose under fairly low pressure can be used. Perform a complete flush if it hasn't had one in a while.
    The ATC probably doesn't use a Max-A/C in-line water valve to close the heater core flow. Diagnose the cooling system first.
     
  9. MoPar~Man

    MoPar~Man Active Member

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    If the heater hoses are about an inch in diameter, located side-by-side high in the middle of the fire wall, then there isin't enough room between the engine intake manifold and the ledge under the windshield for me to get my hand in there to feel them (at that location anyways). Maybe elsewhere.

    And where do I disconnect them in order to flush the heater core? There isin't enough room for me to get to the band clamps at the firewall.
     
  10. ImperialCrown

    ImperialCrown Moderator
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    The wiper arms, cowl screen and wiper linkage can be removed for better access to the heater hoses and the steering gear area.
    The cab-forward design made components in the firewall area difficult to get at, but having the wiper frame out of the way gives you enough room.
    See p. 8K-17 here for 'wiper frame assembly' removal:
    http://oskin.ru/pub/chrysler-dodge/...2000_LH_LHS_300M_Concorde_Intrepid/ELH_8K.PDF
    It may look difficult to remove this assembly the first time around, but it can be easily removed in a few minutes once you know how.
     
  11. MoPar~Man

    MoPar~Man Active Member

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    So here's what I know:

    Added about a cup's worth of antifreeze to the plastic coolant fill-tank (or overflow tank, what ever it's called) this morning before going anywhere. That brought the level in the tank right up to the neck of the tank. After a 10 minute drive (ambient outside temp about 32f) dashboard temp guage was at the 3/8 mark (that's where it always is when the engine is up to temperature, exactly 3/8 mark). Interior temp control set to "Hi" (full heat). Floor and dashboard heat selected. Fan set to midpoint speed. Air blowing out of center vents feels barely warm. Park the car, engine still running, open the hood. I can get my hand around the driver's side heater hose, in some places it's too hot to hold constantly, in other places I can, but just barely. On the passenger side, I can get a thumb and finger around that hose near the firewall, and it's too hot to keep in continuous contact.

    Should I trust the ATC diagnostic that the blend door is working? Is it easier to monkey with that, and leave the core flush as a last resort, or should I just move right to a core flush?

    (can I assume that the heater core fins don't need cleaning if the A/C blows cold?)
     
  12. Int

    Int Active Member

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    In addition to adding coolant you should bleed any air out. The bleeder valve is front and center on the engine.

    I have the same engine in my R/T. If the coolant level is low I get little to no heat at idle but about normal heat while moving. Adding coolant without bleeding can cause the added coolant to simply run out of the overflow in the plastic tank.
     
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  13. floridaman2013

    floridaman2013 Active Member

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    Since you stated that both in and out heater hoses are too hot to hold for long says to me the heater core is getting the hot water but not blowing the air through it into the right spots. Time to check the heatr/ac box and vents to see where it going.
     
  14. MoPar~Man

    MoPar~Man Active Member

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    So right now I've got most of my dashboard apart, the center console completely removed. Needed to remove the center console so that I could slide out the forked rear floor vent supply tube so I could remove the riser for the supply tube so that I could access one of the 3 screws holding the blend door motor.

    I have the blend door motor hanging (still connected to it's electrical connector) and performed the 3-button ATC test. I watched the motor gear turn in one direction and then back again during the test. After the test, the ATC displayed coded 23 and 32. (I figured out how to show the second code by figuring out what the "panel mode button" was. That's the button you press to get air out of the dashboard vents (ie - the opposite of the floor vents).

    So I assume that the ATC gets feedback from a sensor inside where the blend door is, and naturally it's not going to be moving right now. Code 23 is "Blend Door Actuator Feedback Failure", code 32 is "Blend door Actuator Stall Failure". In the unlikely event that someone knows the answer, I'll ask if getting both those codes is normal when the blend door motor is disengaged from the door. ?

    Prior to taking anything apart, the ATC test gave no codes.

    I tried to use a variety of objects to see if I could insert something into the star-shaped hole to try to turn the blend door manually, but there wasn't enough space in that area for me to do that. I was able to get a finger on the bearing or gear or what-ever it is in that hole that engages the motor shaft and push up on it - there was a little play, maybe 1/16 inch and it moves easily enough up and down.

    So unless I'm wrong, it doesn't seem I can do anything else in terms of trying to get a look at the innards of the blend door area or the heater core itself without taking the entire dashboard (what the service manual calls the instrument panel assembly).

    Can the entire air-handling unit (figure 28 on page 25 of the hvac section of the manual) be removed without taking the instrument panel out?

    Is there any point in doing any investigating from the windshield air-intake area (and as far down as is possible to see or reach) to see if there's anything interfering or causing lack of heat (or too much outside air) entering heater box?
     
  15. MoPar~Man

    MoPar~Man Active Member

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    So with the blend door motor back in, the ATC diagnostic gives no codes.

    One thing I notice is that with the fan set to some constant setting (say the mid point) and with the mode set to upper vent (air coming out the dashboard vents), AC is set to off, no defrost or anything like that, and if I run the temp control from "Lo" to "Hi", the fan speed changes abruptly at some point as I'm changing the temp. Engine is still cold, ambient temp is 50 - 55f. Fan is blowing air about twice as hard when the temp is set to Lo and as I raise the temp up to Hi the fan speed seems to slow (or, less air is coming from the vents). I don't know if the fan motor is running slower or if there's something obstructing air flow as the blend door forces more air through the heater fins, and is this reduction expected or is it related to my lack-of-heat problem.

    In other words, without changing the fan speed control there is more air blowing out the vents when the temp control is set Lo vs when it's set to Hi.
     
  16. ImperialCrown

    ImperialCrown Moderator
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    The position (feedback) sensor is inside the actuator, hence the 4 wires. 2 wires the run the motor forwards or backwards (polarity swaps) and 2 for the position sensor.
    Without the stops of the blend door, the actuator probably ran from end-to end (too far) when it was off.
    See p. 273 in the body diagnostics manual. Component locations and wiring diagrams are at the back of the manual. There is a lot of information about how tests are run and faults set in this manual.
    http://oskin.ru/pub/chrysler-dodge/...ntrepid/LH_Body_Diagnostic_Manual/ELH_BDY.PDF
    The BCM also can store ATC fault codes, but you may not be able to read those without an advanced scan tool.
     
  17. MoPar~Man

    MoPar~Man Active Member

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  18. ImperialCrown

    ImperialCrown Moderator
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    All HVAC housings are somewhat similar, but PL is Neon and that pdf could be misleading. You want LH.
    I get Chrysler parts and service manual information from the oskin.ru website.
     
  19. patricklynch

    patricklynch Mopar starship captain

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    Things that look impossible under the hood suddenly become fairly easy once this cross piece is removed. It's surprisingly easy, and I've had enough repairs this year to know. Removing this is the only way to get to the heater core hoses, the rack and pinion, inner tie rod ends, fuel lines going up to the throttle body and more. I've been having heater issues with my 2002 Concorde ever since I got it three years ago. The only shop that had any luck at least partially unclogging my heater core told me that the LH core tubes are smaller than the old stuff and easier to clog. I don't know if that's true or not, but it wouldn't surprise me. One thing I do know, it would have nice if that core could have been removed/replaced without having the drop the whole dashboard. I guess it isn't much worse than pulling the heater box from a '67 Sport Fury. I know car makers are going to do what's most convenient for them but you'd think certain parts like heater cores would be put somewhere more service friendly for their own repair techs if not us.
     
  20. Doug D

    Doug D Virginia Gentleman

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    Unfortunately, replacing the heater core on many vehicles requires removing the dash to access the HVAC box, not to mention having the freon evacuated prior to doing the work. (Might as well replace the evaporator while you have it apart).

    I did have one vehicle that had easy access to the heater core - a 1993 Aerostar. Simply remove the heater hoses at the firewall (quick disconnects), remove the glove box, remove the panel behind the glove box and low and behold there's the heater core. It was recommended to use new quick disconnects for the heater hoses though. It was the one thing on that van Ford did right.
     
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