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 help!
-Wayne
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 display.
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
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
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:
-David
Wayne wrote:
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