Almost non-existent heat

Discussion in 'General Motoring' started by Wayne, Dec 6, 2007.

  1. Wayne

    Wayne Guest

    I recently purchased a 99 Saturn SL 5spd SOHC from a private owner. I am
    having problems with the heater. I can drive 25 miles and still have almost
    no heat. It takes forever to clear a frosty windshield. The previous owner
    said he flushed the cooling system and put in a lower thermostat. Would
    that be the problem with the heater or is it unrelated? If it is a
    thermostat, where is it located on the Saturn? Thanks in advance for your

    Wayne, Dec 6, 2007
  2. Wayne

    Oppie Guest

    No reason I can think of to use a different temperature thermostat than
    stock. The ECU is set to expect a given temperature and below that, it calls
    for mixture enrichment (akin to the choke on carbureators). What is the
    engine temperature? You can have a shop read out the Coolant temperature
    from the obdii or simply feel the radiator hoses to see how hot they get. If
    the block temperature is in range, then look for fouling / blockages inside
    the heater core. Feel the hoses going to the heater core and see how warm
    they are in relation to the radiator hoses. There should also be a
    temperature difference between the heater inlet and outlet hoses. This is
    where one of those neat Infrared thermometers is really nice - point the
    laser dot on the surface to be measured and read the temperature from the

    Does the heat control knob have a normal feel? It operates a flap that
    either forces all the air though the heater core (hot) or arround it (cold).
    If something is wrong here, the heater core may not be getting the airflow
    expected. In this case, you will get a low temperature differential on the
    core inlet and outlet hoses.

    Some vehicles also had a booster pump in the heater coolant line. I have
    this on my L series. I disconnect it (electrically) in the summer (long
    story) and re-connect it in the winter. If I forget to re-connect it, takes
    a much longer time to heat up the cabin.

    Hope this helps
    Oppie, Dec 6, 2007
  3. Wayne

    Bob Shuman Guest

    The lower thermostat value is certainly not helping you here. Replace it
    with the original value. That said, the other obvious culprits could be low
    coolant level, or trapped air in the system. If none of these is the issue,
    then you will need to check for a blockage in the system.

    Good luck.

    Bob Shuman, Dec 7, 2007
  4. Here is another datapoint. I had some problems with the heat in my 1995
    SW1 when I bought it. I was able to track it down to a bad thermostat
    housing, see this thread:

    Last May I put in a new radiator due to a small crack in the plastic
    housing. Last week when I was driving the car to the junkyard it had
    the best heat it had ever had. So it kept me warm for it's last trip.
    (and one of the rear wagon side windows was gone, and the car was still

    David Teichholtz, Dec 7, 2007
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