Hello, Allpar Forums member or visitor! If you were a member, you would not see this ad!

Register or log in at the top right of the page...

  1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

It's winter, so heater problem is back ('00 300m)

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Dec 20, 2016.

  1. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    So we've had a week or two of very cold temp's around here (5f at night, maybe a high of 10 or 12 f some days). Temps that in a "normal" winter we might see in late January.

    I've stuck a temp sensor in the center grill of the dashboard vent of my '300m and have the temp control set to "Hi" and the fan set to maybe 25% speed. I' have 3 readings so far, (outside temp / inside vent temp):

    50/104
    32/94.5
    12/82.4

    These are in (f). Inside temp is when engine has been up to full temp (as indicated by engine temp guage) for at least 20 minutes. 3 points, but very linear line. For every increase / decrease of 1 degree f of outside temp, there is a change of about .5 degree in the max heat that I get out of interior center vent. Interior air temp inside car is (I would guess) no colder than maybe 50f when these readings are made. Car is kept in heated garage overnight so the car interior temp is at least 50 - 55f when I start my short morning commute of about 5 - 10 minutes.
     
  2. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,948
    Likes:
    3,336
    I wish I had readings this good. What is wrong, in your opinion?

    First, with colder temperatures, it will take longer to get the heater core up to a given temperature. Second, the higher the fan speed, the faster the heat transfer (or rather, the cooling) of the heater core. So it's possible at high fan speeds to make the heater core temperature drop. With colder outside air flowing over it and a higher fan speed, the block and radiator cannot transfer heat fast enough to keep up. So I don't see anything wrong.

    Currently my heater core is clogged, and I'm driving 40 miles each way to work with virtually no heat, so if you want to trade until spring....
     
    Doug D likes this.
  3. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    I should add that my readings were taken when the "closed-loop" (recirculation) air setting was NOT engaged. How the system controls the air-blend door in response to the desired interior set-point (including "Hi" setting) and exterior temp - and whether this response can ever become faulty - is something I'd like to know.

    > Currently my heater core is clogged, and I'm driving 40 miles each way to work with virtually no heat, so if you want to trade until spring....

    Is that your Daytona, or Dakota?

    Trust me. A weak breeze of 82 f is not all that warm and doesn't do much inside when it's 12f outside.

    One thing I notice is that the interior vent temp will drop a degree or two when I park the car but keep it idling. In other words, any extra exterior air that I'm forcing through the air intake system while driving (ie - cooling effect) is not lowering the interior vent temperature as much as being parked but with the engine running at idle. So a higher engine RPM is giving me a slightly warmer vent temp despite the cooling effect (if there is one) of the car moving forward at city driving speeds.
     
  4. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,948
    Likes:
    3,336
    You said your commute is 5-10 minutes. At those temperatures, and that short a trip, you are never going to get the maximum heat possible out of the core.

    My 84 Daytona is the one with a clogged core. My 92 Dakota has a replacement core that I put in last year, and can start a brush fire, so much heat comes out of it. At highway speeds, I don't even need the fan on to be smothered in heat.
     
  5. Doug D

    Doug D Virginia Gentleman

    Joined:
    Aug 10, 2000
    Messages:
    12,231
    Likes:
    1,720
    I agree with Bob. A relatively short 5-10 minute trip doesn't really allow the engine to get up to complete operating temperature. Yes, it may have heat, but it's not at full capacity yet. I have a 90 minute commute, and I sometimes make a stop for fuel/coffee about 5 minutes from the house. On a cold 20 F morning the heat in my truck is just starting to get warm. And that's letting idle for 30 seconds to a minute after starting, then putting it in gear and going. It takes another 10-15 minutes to get good heat.

    I don't have a temp sensor to place in the vents, but I'd venture my 2006 Ram 1500 puts out about 85-90F heat (possibly hotter) in 20 F temperatures after 20 minutes (it's usually at operating temp by then). It can quite toasty in the cab (keep in mind its a quad cab) such that I have to reduce the heat and cut the fan speed back. IF I think of it I may pick up a small temp sensor to place in the vents to see what the actual heat output is.

    I feel for you Bob. In the January 2003 the heater core in the '92 Acclaim began to leak (had ~301K miles). I T'd the heater lines together bypassing the core. I ended up driving it for about 6 weeks until I found a inexpensive '90 Acclaim for $300 (only 110K miles, but had peeling paint). During that 6 weeks I was driving the '92 I hada blanket on my lap and gloves on. I really froze when I had to use the defrost (AC still worked) to help clear the windshield.
     
  6. LouJC

    LouJC Active Member

    Joined:
    Oct 7, 2014
    Messages:
    522
    Likes:
    371
    I agree with the point that you are not driving long enough for the engine to even fully warm up and you will never get the max heat the system is capable of producing under those conditions. I'd make sure first that your engine is reaching normal operating temp (I use an IR temp gun for checking this at the thermo housing) and that there are no small coolant leaks (this can be a cause of air in the system, which will cause low flow through the core and a lack of adequate heat transfer). We had this on our '98 ZJ Jeep when there was a rad leak, then I fixed that with a new rad. A few years later had it again, when the heater core leaked. However, with a new rad and core, that Jeep gets really toasty inside, quite fast!
     
  7. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    I have a 5 - 10 minute commute to work in the AM. The car (the entire car) has been warmed to 50 - 55 f in the garage overnight. I mention that because the weak amount of heat that the heater is apparently capable of generating *at any time* is not a big issue for at least half the driving I do in the winter. The temp readings I gave earlier are for when I've been driving for an extended period of time during other parts of the day (I though I mentioned that the temps were measured after at least 20 minutes of the engine being at full operating temperature). There are no coolant leaks. The radiator is less than 2 years old, and hence the coolant is also less than 2 years old. The rad hoses are roughly 6 years old (that's when I had the timing belt changed, along with replacing the water pump and thermostat just because why not).

    One thing I notice about the air-recirculation mode (closed cabin air recirculation) - it seems that the A/C comes on when I set it to that mode. Standing still at, say, a stoplight, hitting the air-recirc mode to on seems to increase the engine idle speed slightly, the fan blower blows a little stronger (even though I don't touch the fan speed knob), I smell that "A/C smell" in the air, and get the physical sense that the A/C compressor was activated. Now I don't know if that's supposed to happen when the air-recirc mode is turned on. I'm thinking that only other people with 300m or LHS would know the answer (maybe Intrepid too?).
     
  8. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
    Level 2 Supporter

    Joined:
    Jul 10, 2002
    Messages:
    29,948
    Likes:
    3,336
    My wife's 2012 Chrysler 200 turns on the A/C automatically when you activate the Recirc and turn the fan on. You have to turn the A/C off manually in that case.
     
  9. Doug D

    Doug D Virginia Gentleman

    Joined:
    Aug 10, 2000
    Messages:
    12,231
    Likes:
    1,720
    Has it always been this way? Or something you've noticed lately? Does the heat not feel hot enough? Maybe it's just that way. I had a '79 Monza that while the heat was adequate, could struggle to put out heat in bitter temperatures (sub zero) and did okay in sub freezing temps (below 32 F). By contrast our current vehicles ('06 Ram and '10 Journey) can eventually roast you out with ambient temps below 20 F. (We rarely see sub zero temps here in VA - coldest I remember in recent history is about 0-10 F)
     
  10. peterjon1

    peterjon1 Well-Known Member

    Joined:
    Aug 14, 2004
    Messages:
    1,121
    Likes:
    81
    A couple possibilities come to mind. Perhaps your heater core is partially plugged, or maybe the blend door is not functioning correctly.
     
    floridaman2013 likes this.
  11. Doug D

    Doug D Virginia Gentleman

    Joined:
    Aug 10, 2000
    Messages:
    12,231
    Likes:
    1,720
    I can't remember for sure since I parted with the cars several years ago, but I sort of recall that when I would put it on Recirc, on the Acclaims I had ('90 and '92) it automatically engaged the AC. Perhaps I'm thinking of something else. I do agree that if the AC is engaged (for AC operation or defrost) the heated air is "different".

    About the only things I can think of regarding the heated air temp are low coolant level, partially clogged heater core, or a blend door issue. Maybe back flushing the core (gently) will remove any built up crud. The car is 16 years old.
     
  12. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    > Has it always been this way? Or something you've noticed lately?

    Last winter was mild, but the previous two were nasty. This is probably the 4'th or 5'th winter where this weak-heat problem has been noticable.

    > Does the heat not feel hot enough?

    No. The Hi setting is (presumably) full-blast heat, and in the summer when I've tried that (without measuring it) it is VERY hot. The temp. of the air coming out of the vent is definately proportional to ambient.

    I just finished a 2-hour highway ride tonight. Car was soaking in out-door temps for past 3 days, so it was about 30f at the start. Ambient outdoor temp during the trip was 28-30 f. By about an hour into the trip I would say that the cabin interior was "pleasant" - maybe a degree or two colder than I would have liked. I had the air set to floor and dash vents, temp set to "Hi", fan set to 25%. Dash center air temp (sensor stuck inside vent louver) read 95f pretty much constantly. Despite having temp set to Hi during entire 2-hour trip, cabin interior reached I would say 68 - 70f during the first hour of the trip and didn't climb any higher. Overhead info display sez I'm getting 28 - 30 mpg during this trip (slight tailwind). This it typical of what I see on the highway. My speed is cruise-control set to 70 mph.

    Something else I notice - is the fan knob or decal around the knob supposed to light up to give some indication of the knob position? I'm not seeing anything to indicate fan-knob position during night driving.
     
  13. Doug D

    Doug D Virginia Gentleman

    Joined:
    Aug 10, 2000
    Messages:
    12,231
    Likes:
    1,720
    I'm not sure about your model but there is probably small bulbs behind the control panel that have probably burnt out. All but one or two of them have burnt out on my Ram.
     
  14. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    > is the fan knob or decal around the knob supposed to light up to give some indication of the knob position?

    Ok, I've taken the hvac panel off the dashboard and yes, there are 3 extremely small incandescent bulbs that provide back-light for the 6 rocker buttons and 1 bulb specifically for the fan knob. And while there are 2 surface-mounted LED's on the board for the front and rear defrost indicators, there is no sane reason I can think of that these 4 other lamps were chosen to be incandescent rather than LED bulbs. I'm going to replace this bulb with one of the dozens and dozens of led's in my horde of electronic parts bins - anyone know what value dropping resistor I should use? What's the voltage on the bus that powers these lights?
     
  15. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    The voltage these little bulbs get is 9.5 V (engine not running) and 10.75 V (engine running at idle). I chose a Cree 5 mm round led (c535a-wjn-cu0v0231) which is probably out of production but spec wise it's got a voltage drop of 3.2v and current of 20 ma. So I chose a resistor of 390 ohms and soldered it directly to the PCB. The fan knob indicator now has a slight blue tint to it, a little different than the greenish tint from the other indicators.
     
  16. peterjon1

    peterjon1 Well-Known Member

    Joined:
    Aug 14, 2004
    Messages:
    1,121
    Likes:
    81
    So is there actually more air movement, or does it just sound louder (which it will, because a flap has opened under the dash to draw air from in the interior.)
    In my Stratus, center vent temps on full heat are 140 deg F or higher, blower set on 2 or 3. This is with all airflow directed to the vents. I recall the system is designed to direct more heat toward the floor, if both the floor and dash vents are in use.
    Are you sure that your engine is reaching full temp of 195F?
     
  17. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    > > Standing still at, say, a stoplight, hitting the air-recirc mode
    > > to on seems to increase the engine idle speed slightly, the fan
    > > blower blows a little stronger (even though I don't touch the
    > > fan speed knob),
    >
    > So is there actually more air movement, or does it just sound louder

    It feels like there is slightly more air movement in recirc mode.

    During steady state, flat highway driving, hitting recirc mode (which I do when I pass a certain landfill) knocks 1 or 2 MPG off the fuel economy reading, which again tells me the A/C compressor kicks in for some reason.

    > Are you sure that your engine is reaching full temp of 195F?

    Dashboard temp indictor dial is marked off in 1/8 increments, with the last 7/8 increment colored with red background. The needle always points to the 3/8 line, always, winter or summer. In 16 years of owning this car I've never seen it at any other location to indicate what I have to believe is normal operating temp.

    I'm going to see if I can tape a couple of temp sensors to the heater inlet and outlet hoses at the firewall and rig it up so I can read the temps while driving.
     
  18. peterjon1

    peterjon1 Well-Known Member

    Joined:
    Aug 14, 2004
    Messages:
    1,121
    Likes:
    81
    Ok, so it seems like engine temp is good, and slightly more air movement in recirc is ok, meaning there is not a drastic difference, which could show problems in the ductwork. AC on in recirc is desirable, because the air needs to be purged of the moisture that will build if less fresh air is being introduced. As an illustration, I had a van in which the recirc door became stuck, and the AC was broken. In cold weather, the windows would fog rapidly, so I had to open a window until I fixed the recirc door. It will be telling to see the heater hose temps.

    This "One thing I notice is that the interior vent temp will drop a degree or two when I park the car but keep it idling. In other words, any extra exterior air that I'm forcing through the air intake system while driving (ie - cooling effect) is not lowering the interior vent temperature as much as being parked but with the engine running at idle. So a higher engine RPM is giving me a slightly warmer vent temp despite the cooling effect (if there is one) of the car moving forward at city driving speeds" makes me think the heater core may be nearly plugged, needing higher RPMs to force more coolant flow.

    Interesting tidbit, I had a Spirit that had a plugged heater core. It was plugged with rubber particles from the inside of the radiator hoses. Hoses looked fine on the outside, but they were coming apart inside.

    Random thought, does the 300M have a control valve in the heater lines that could be malfunctioning?
     
    #18 peterjon1, Dec 30, 2016
    Last edited: Dec 30, 2016
  19. Doug D

    Doug D Virginia Gentleman

    Joined:
    Aug 10, 2000
    Messages:
    12,231
    Likes:
    1,720
    I'm pretty sure the control valve was gone on most models by 2000. My '90 Acclaim had it while the '92 Acclaim I had did not. Both had the 2.5L engines. There was no control valve in my '00 T&C Ltd 3.8L either.
     
  20. MoPar~Man

    MoPar~Man Member

    Joined:
    Jul 9, 2014
    Messages:
    130
    Likes:
    9
    I don't think there's any control valve in the 300m, which means hot coolant flows through the heater core all the time, even in the summer.

    I have put temp sensors on the heater hoses, wrapped with a few turns of electrical tape. Initial readings show hose A at 140f and hose B at 133f (hose A closer to passenger side). Outside ambient at 37f. Engine was up to temp after short round-trip, but not for very long, but had been idling for 5 min. I'll see how these numbers change under other conditions...
     

Share This Page

Loading...