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

"Wayne" <wayne (AT) spam (DOT) com> wrote

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

"Wayne" <wayne (AT) spam (DOT) com> wrote

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:

http://groups.google.com/group/rec.autos.makers.saturn/browse_thread/thread/ce616b2ceac09dd3/dd31221b8ce15223?hl=en&lnk=st&q=teichholtz+heat+sa turn#dd31221b8ce15223

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
warm!)

-David



Wayne wrote: