--- title: What happens during a normal operating cycle of a Velit gas or diesel air heater description: What happens during a normal operating cycle of a Velit gasoline or diesel air heater from startup to shutdown. --- [Skip to content](https://help.velitcamping.com/help-articles/what-happens-during-a-normal-operating-cycle-of-a-velit-gas-or-diesel-air-heater#main-content) ![Velit](https://help.velitcamping.com/hs-fs/hubfs/460684741_1701809850568731_4111707878241104706_n.jpg?width=150&height=150&name=460684741_1701809850568731_4111707878241104706_n.jpg) - [SHOP](https://velitcamping.com/) - [CONTACT US](https://velitcamping.com/pages/contact) - [HELP CENTER](https://help.velitcamping.com/help-articles) - SUBMIT TICKET Show submenu for SUBMIT TICKET - [Heater Support Ticket](https://velitcamping.com/pages/heater-tech-support-request) - [AC Support Ticket](https://velitcamping.com/pages/ac-tech-support-request) Open main navigation Close main navigation - [SHOP](https://velitcamping.com/) - [CONTACT US](https://velitcamping.com/pages/contact) - [HELP CENTER](https://help.velitcamping.com/help-articles) - SUBMIT TICKET Show submenu for SUBMIT TICKET - [Heater Support Ticket](https://velitcamping.com/pages/heater-tech-support-request) - [AC Support Ticket](https://velitcamping.com/pages/ac-tech-support-request) - [Back to Velit Website](https://velitcamping.com/) [Back to Velit Website](https://velitcamping.com/?hsLang=en) How can we help you? - There are no suggestions because the search field is empty. 1. [Velit Customer Support](https://help.velitcamping.com/help-articles?hsLang=en) 2. [FAQs](https://help.velitcamping.com/help-articles/faqs?hsLang=en) 3. [Velit Air Heater FAQs](https://help.velitcamping.com/help-articles/faqs?hsLang=en#velit-air-heater-faqs) May 11, 2026 # What happens during a normal operating cycle of a Velit gas or diesel air heater ## After pressing the center button 2S (seconds) to start, what is supposed to happen with the heater as it starts up, runs, and shuts down? ### **PRESS 2S (seconds) TO START** On the Thermostat Controller, press the center button down for two seconds to start the heater. You may also use the phone app to start the heater with the power button at the bottom of the screen. ### **Fan** Starts Immediately Once the heater is started, the fan motor begins turning the fans immediately. The fan speed will vary depending on firmware version and settings. ### **Glow Plug** Heating roughly 45 Seconds During the first approximately 45 seconds, the glow plug will be slowy heating red hot. This is high amperage draw phase of startup of 10-15+ amps.  ### After approx. 30 to 60 seconds: **Fuel Pump** Clicking Begins Only once the glow plug has had time to be slowly heated to get red hot, will the fuel pump begin clicking to dose the atomized fuel onto the hot glow plug. ### **Combustion**, Heat Produced Once the atomized fuel is ignited, the fans, along with the continuous pulse of the fuel pump keep the flame alive.  ### **Glow Plug** Turns Off Once the temp sensor detects warmth, the glow plug is turned off and the power draw goes down significantly. ### **Fan & Fuel Pump** maintain combustion flame, producing heat The heater will continue to run with just the fuel pump and the fans until thermostat reaches set ambient temp. Or will run continually in manual mode. ### Heater **Shutdown** When the heater reaches set temp or is turned off, that is accomplished by the fuel pump stopping, allowing the flame to go out. ### Heater **Cooldown** The fans remain running to cool the heat exchanger and heater internals to a safe temp. Cooldown time depends on various factors, always allow the heater to run a complete cooldown cycle. ### Heater **Restart** When the ambient temp drops approximately 5 degrees below the set temp, the heater will restart itself following the same order as above, beginning with fans and glow plug heating.   **Possible improper startup scenario:** If the combustion step above does not happen, or is interrupted, the heater will slow down, attempt to heat the glow plug, and restart itself 1 more time. If it is unable to restart, it will throw an E02 combustion interruption. This is almost always caused by improper fuel delivery due to issues with fuel lines.   Useful video:   - [Troubleshooting](https://help.velitcamping.com/help-articles/troubleshooting?hsLang=en#main-content) - [Heater Troubleshooting](https://help.velitcamping.com/help-articles/troubleshooting?hsLang=en#heater-troubleshooting) - [A/C Troubleshooting](https://help.velitcamping.com/help-articles/troubleshooting?hsLang=en#a-c-troubleshooting) - [Product Manuals](https://help.velitcamping.com/help-articles/product-manuals?hsLang=en#main-content) - [Velit Air Heater Manuals](https://help.velitcamping.com/help-articles/product-manuals?hsLang=en#velit-air-heater-manuals) - [Velit Air Conditioner Manuals](https://help.velitcamping.com/help-articles/product-manuals?hsLang=en#velit-air-conditioner-manuals) - [FAQs](https://help.velitcamping.com/help-articles/faqs?hsLang=en#main-content) - [Velit Air Conditioner FAQs](https://help.velitcamping.com/help-articles/faqs?hsLang=en#velit-air-conditioner-faqs) - [Velit Air Heater FAQs](https://help.velitcamping.com/help-articles/faqs?hsLang=en#velit-air-heater-faqs) - [Comvolt Power Station FAQ](https://help.velitcamping.com/help-articles/faqs?hsLang=en#comvolt-power-station-faq) - [General](https://help.velitcamping.com/help-articles/general?hsLang=en) - [Shipping & Fulfillment](https://help.velitcamping.com/help-articles/shipping-fulfillment?hsLang=en) - [Product Questions](https://help.velitcamping.com/help-articles/product-questions?hsLang=en#main-content) - [Velit Air Heater Product Questions](https://help.velitcamping.com/help-articles/product-questions?hsLang=en#velit-air-heater-product-questions) - [Velit Air Conditioner Product Questions](https://help.velitcamping.com/help-articles/product-questions?hsLang=en#velit-air-conditioner-product-questions) [![Velit](https://help.velitcamping.com/hs-fs/hubfs/460684741_1701809850568731_4111707878241104706_n.jpg?width=150&height=150&name=460684741_1701809850568731_4111707878241104706_n.jpg "Velit")](https://velitcamping.com?hsLang=en) Copyright © 2026,