Dyna-Glo 8001ss runs OK on 1lb tank but shuts down...

Question

The heater runs ok with the 1 lb tank, no problems whatsoever, but very intermitent with the 20 lb tank. Sometimes it runs for 10-15 minutes or longer, other times it continues to shut down as soon as I move from pilot to run. I can hear a faint click sound when it shuts off but can't figure out what it is or what might be causing that. The hose from the 20lb tank appears to be clear of blockage. I have tried 3 different tanks with the same results.