I have a ventless gas wall heater in the basement. Should I let the pilot light burn all thevtime, even in the summer when I am not using the heater?

call a gas fitter for the repair
could be a freezing of the gas because of a blockage that is restricting gas flow
gas is not a diy repair

Make Sure Pilot Flame Is Long and Blue and hitting Thermocouple Head Good---If Thermocouple Head Is Too Short (from wear) Check Length and Configuration and Purchase New One From Hardware Store Or Related (like home depot) IF ALL LOOK OK, CHECK FOR A SWIFT AIR DRAFT (that will blow out pilot) My Dog Walks By And BLOWS Mine Out.

Blow the thermocouple out with an air compressor while the unit is off. Another way to clean it is with a CO2 BB gun. Make sure it's not loaded! lol!

my vanguard ventless gas space heater making a toxic smell

Hi clean out tiles with air line clean pilot / if still goes out check thermocouple

weak pilot flame: should wrap around therocouple.
blue flame with yellow tip not yellow and lazy.
if flame good replace thermocouple

Try to take pilot assembly apart and clean real good. This will work most of the time. If it does not work for you, you will need to replace the gas valve. It's expensive but I'm about positive that cleaning it will fix it. Gas burns dirty and after a couple seasons a scale builds up that causes this problem. It's pretty common and nothing to worry about after it's cleaned. Good luck.

make sure you have the gas valve knob on turned to pilot while pressing that down while pushing the spark it should light or it is tripped on a safety like rollout switch or oxygen depletion sensor if equipped which all ventless heaters are

I have several of these heaters in my rent houses and love them. The most problem I have is not being able to ignite the pilot with the user control igniter. Remove the screws that hold the front cover in place along with the front cover. Hold the pilot control down and ignite with a lighter. Keep the pilot engaged until thermocouple is warm enough to keep pilot gas flowing. If it will light this way then you need to blow out the pilot orifice. It seems that every year I have to go in after the summer season when the heater is off and clean the pilot/orifice lines with high pressure air. I believe spiders/bugs/dust block pilot orifice when it is not in use. You can also tell that orifice is blocked when you don't get a good blue pilot flame with pressure behind it allowing the flame to submerse the thermocouple. If the the thermocouple is not getting enought heat it will turn pilot gas off for safety reasons.