take the plastic side cover off.
you don't . customer service is terrible. out of stock on circuit boards that go bad and no answer when they will be available.
REPLACE MAIN BOARD..I AM ON MY 3RD FOR SAME THING....
I would recommend referring to your manual here is the link https://drive.google.com/file/d/0B51URkAbkqnhMzczUGtndDh0MGs/view. You can also contact ProCom Heating 1-866-573-0674
The main board is junk..you will need to replace it..
Hello, Thank you for your message. We apologize for the delay is response. Please reference the instructions in the manual for troubleshooting the C1 code. If you are unable to fix the unit, please give us a call at 866-573-0674 Monday - Friday from 8am to 5 pm CST for further assistance with the product. Please let us know if we may assist you further, Procom Heating
Manual is at: https://www.usaprocom.com/customer-service-center/product-manuals/. My 1st c9 was a bad motor, My 2nd c9 was the air pump vane began to rub. if you are lucky you may be able to adjust the tolerance - page 17 of the manual - and get it running. My advice however is to find a new heater, mine has been nothing but trouble.
Your question makes no sense. you use either Diesel or Kerosene. Ina closed space through diesel will choke you out though, Kerosene burns much cleaner