if it runs off a "jump pack" [battery] it's a battery or cable problem re-check all your connections, sounds like the cables are not tight on the terminals or you've gotten bad batteries or hooked it up backwards
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics