OK, did a archive search, a few posts on the problem but no real
information.
If your main heater (the one in the dash) only works on the high
speed then the resistor pack has failed. The dealer may ask for $30
or more for a new resistor pack but the thermo fuse itself is widely
available and costs about $1. While it is possible that the resistors
are burned out it is also possible that the thermo-fuse (AKA TCO,
thermal cut off) has blown. This is easy to replace after you remove
the glove box.
1. Disconnect the ground cable at the battery. Safety first!
2. Remove the glove box.
3. There is a 4 position connector just to the left of the blower
fan motor. Under this connector is the resistor pack. Remove the
connector.
4. Remove the single screw that fastens the pack to the blower
housing and remove the pack.
OK, if the resistor pack is all burnt up you will need a new one. But
if all looks good but there is no continuity between terminals 1&4
then the thermo-fuse is blown.
thermo-fuses are available from many electronic supply houses. Look
on the side of the old thermo fuse for a temp rating. Mine was rated
for 216c. Pretty hot! Radio shack lists only low temp units, Don't
use anything with a lower rating. I recommend equal or higher, but
not too much higher. Newark electronic carries them, price less then
a dollar. The package will have instructions and may say not to
solder but to crimp it on. Thats up to you, I bought two :) and had
no problem soldering the first one. Cut the old thermo fuse off,
clean the resistor leads and solder the new one in place. Just use
good soldering practices (heat sinks) and tin the resistor leads
first.
