My glowarm ventless heater keeps going out after being on for a few minutes what can I do to fix it

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!

You wont hear gas coming through until you depress the control knob. Otherwise try another tank. The ball valve may be stuck in the one you're using.

A can of air, vacuum and a long thin brush. Blow out any debris in burners and at the pilot assembly while running the vac. Brush all parts you can get too. Unscrew the pilot line from gas valve and blow in tube with can of air. Fire up heater and check for CO.

Ventless Gas logs, Vanguard, VS30PR. Propane gas
Pilot light stays lit various times, sometimes for several days then other times for a few minutes. Lights best when temp outside is below freezing. Pilot flame appears to receive too much air. How do you adjust the pilot flame? Is this done using two screws marked A & E? Do you have suggestions?
Thanks,
Ed

I would look closely at pilot flame, if flame is lazy and yellow,repace the OD S pilot assembly.You can order from 1-800-654-8534

The thermocouple may be worn out.
The thermocouple may have come loose from the valve.
The ODS pilot may be clogged with dust or lint and may need to be cleaned with air(less than 30psi)
The valve or regulator may be faulty.

if it makes a kind of grinding noise then the internal brushes for the motor are going bad, if it rattles and vibrates a lot then the fan blades have been knocked out of balance.

check the regulator.

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.