Hello i have an older co ray vac low intensity tube heat system that I have been working on. It has 2 Linier burners on the branches. (4"tube) One I can't get the main burners to lite, only the pilot. my vac is between 4 and 4.5 " on the end with ristrictor plate in place. Gas pressure is ok. If i jumper out the flame switch the main burners kick on. I have replaced the mercury flame sensor with no luck. The tip of the flame switch glows red looking at it from the sight glass in the burner tube. I have made sure that the connections are good going from the switch to the main valve. I have cleaned the pilot and sparkplug orffices through the burner. it has a new air filter. I have nothing to go off of as far as btu's model number goes. the tags are nowhere to be found. Everyone i have talked to about this just tells me to give my customer co-ray-vacs number to schedule a service call with them. whitch as much as it shames me todo so I am willing to except defiet. but not until Ive tried everything i can. Any thoughts?