When I turn on the heater and set it to the temperature I want, it goes off when it reaches the temperature. It is not merely in standby, it is off. It beeps repeatedly (when it shuts itself off after being on for a few minutes) at odd intervals. I have tried not setting a temperature for it, and it still goes off after a few minutes of being on. When it shuts off, it will not stay on when I try to turn it back on. I just bought it today. I don't see how it could have a clogged filter or anything, but I have no diagram of the heater or troubleshooting tips to help me sort this out.

answer is in instructions
Save-Smart®
Press () to activate the Save-Smart®Function.
1.Set the thermostat to desired temperature using the +/-
buttons (Note: The default Save-Smart®temperature is 72 ? F)
2.When you reach the temperature at which you want to
set the unit, the set temperature will flash several times
and then the display will return to indicate the current
room temperature and will gradually change as the
room temperature changes.
3.When the air temperature is less than the set temperature,
the heater will run in HIGH heat.
4.Once the thermostat reaches the set temperature the heater
will automatically switch to LOW heat to save energy.
5.When the air temperature reaches 4? above the set temperature,
the heater will turn off. The Heater will cycle off and on in the LOW
mode to maintain the set temperature.
All this happens automatically with Lasko Save-Smart®Technology.
To deactivate the Save-Smart®function, press Save-Smart®
again or (hi/lo) for continuous high/low heat.

AUTOMATIC TEMPERATURE CONTROL(Figure 3)
The automatic temperature function will only operate on "High" heat.
You cannot set the temperature automatically when the unit is in the low heat mode.
1.To set the room at a specific temperature press the () or()buttons
to the desired temperature. The display will now reflect the () and the temperature will be flashing. The Heater is now in Auto Temperature Mode.
2.When you reach the temperature at which you want to set the unit, the set temperature will flash several times and then the display will return to indicate the current room temperature and will gradually change as the room temperature changes. NOTE: the temperature display does not indicate the temperature of the heated air being emitted by the heater.
3.Once the room temperature reaches 2 degrees above the set temperature, the Heater will shut off. Once the room temperature reaches 1 degree below the set temperature, the Heater will turn back on and continue to cycle off and on to maintain the set temperature.
4.This function will cancel if the ()button is pressed. The Heater will now be in High heat and run continuously.
NOTE:It is normal for the Heater "fan" to run for approximately 15 seconds when the Heater shuts off after reaching the set temperature.Press the () and() buttons at the same time to change the display to ° Celsius. Press the same two buttons together again to change the display
back to ° Fahrenheit.

The Little Giant units use a Unitrol gas valve very similar to a water heater in the home. #1,urn the Unitrol gas valve to the "PILOT" position to ignite the pilot. Depress the plunger and hold it down then push the spark igniter button until you can see the pilot flame ignite.
You have a lit pilot so this is not a problem for you.
The pilot light stays on continuously by design.
Once the pilot flame is established, you then turn the on/off/pilot valve to the "ON" position and set the thermostat to the desired temperature range., it should then fire its main burner until the desired temperature is reached. Once the temperature is reached, the main burner will shut off and the heater will go into a standby mode with the pilot flame still burning.
If you have turned the pilot valve to on and set the temperature high, it should come on, if not a new gas valve is required, they can be very difficult to replace due to rust.and most cases require a new unit,

No one ever said new means good. Try another thermostat. Make sure it is the recommended temp for the vehicle. I would spend the extra money to buy a dealer thermostat. What controls temp is restriction of flow thru the system until a set temperature is reached and the thermostat opens. Has to be a thermostat.

It is supposed to. When the heater reaches the temperature you set, it goes off and the indicator light goes off too telling you the heater is off. Soon the temperature drops again and the heater, and the indicator light, comes back on.----This is the working procedure.------ The pressure switch, float switch all needs to be inspected.------- Also what is the exact brand and model of your heater.This will help, to get exact cause of the problem. --------- Keep updated, thanks.Helpmech.

6000 simply means Broken fuser heater lamp wire
The temperature does not reach 100°C/212°F after the fuser heater lamp has been turned on continuously for 30 s. The temperature does not rise by 1°C/1.8°F after the fuser heater lamp has been turned on continuously for 5 s during printing. 35/37 and 45/47 ppm printers (EUR/USAmodel):
Fuser thermistor M detection temperature does not rise by 1°C/1.8°F
after the fuser heater lamp has been turned on continuously for 10 s during warm-up or at standby.Fuser thermistor S detection
temperature does not rise by 1°C/1.8°F after the fuser heater lamp has been turned on continuously for 5 s during warm-up or at standby.
Poor contact in the fuser thermistor M connector terminals.Reinsert the connector (See page P.1-5-19).Fuser thermistor M installed incorrectly.
Check and reinstall if necessary (See page P.1-5-19).Thermal cutout
triggered.Check for continuity. If none, replace the thermal cutout (See page P.1-5-19). Fuser heater lamp installed incorrectly. Check and reinstall if necessary (See page P.1-5-19).Broken fuser heater lamp wire. Check for continuity. If none, replace the fuser heater lamp (See page P.1-5-15).

how do you know it is dropping 100 degrees ?
If the set temperature is 350-400 the heaters will work untill the thermostat will read that the temperature is reached - after that the heaters will shut down and the temperature will drop...and after few minutes when the temperature goes below thw set point (in this case 350-400) the heaters will turn on again - this will happen for the duration of the timing you have selected (example 45 minutes)

thanks for the info. care to try again?

6000 Broken fuser heater lamp wire
The temperature does not reach 100°C/
212°F after the fuser heater lamp has
been turned on continuously for 30 s.
30/31 ppm printer (EUR/USA model):
The temperature does not rise by 1°C/
1.8°F after the fuser heater lamp has
been turned on continuously for 5 s during
printing.
35/37 and 45/47 ppm printers (EUR/USA
model):
Fuser thermistor M detection
temperature does not rise by 1°C/1.8°F
after the fuser heater lamp has been
turned on continuously for 10 s during
warm-up or at standby.
Fuser thermistor S detection
temperature does not rise by 1°C/1.8°F
after the fuser heater lamp has been
turned on continuously for 5 s during
warm-up or at standby.
The temperature does not rise by 1°C/
1.8°F after the fuser heater lamp has
been turned on continuously for 5 s during
printing.
Poor contact in the
fuser thermistor M
connector terminals.
Reinsert the connector (See page P.1-5-19).
Fuser thermistor M
installed incorrectly.
Check and reinstall if necessary (See page
P.1-5-19).
Thermal cutout
triggered.
Check for continuity. If none, replace the
thermal cutout (See page P.1-5-19).
Fuser heater lamp
installed incorrectly.
Check and reinstall if necessary (See page
P.1-5-19).
Broken fuser
heater lamp wire.
Check for continuity. If none, replace the
fuser heater lamp (See page P.1-5-15).

The heater shuts off when it reaches two degrees above the set temperature and turns back on when it is two degrees below.