Velit Gasoline Air Heater Build (4kW)

Written By James & Kaity

Why are diesel heaters so common in North America when most vehicles run on gas?

Velit’s gasoline heater is a great option for those looking to simplify their setup and avoid having to bring diesel (in addition to gasoline and propane).

Here's a step-by-step guide on how to install a Velit gasoline air heater into a Harbor Freight case:

Disclosure: Some of the links in this article may be affiliate links, which means we will receive a small commission, at no additional cost to you, if you decide to make a purchase through one of our recommended partners. We only promote products and services we genuinely believe in. Thank you for your support!

Materials Needed:

Tools Needed:

  • Drill + assorted bits

  • Screwdriver set

  • Hole saws (1 inch, 2 inch, 3 inch)

  • Stepped drill bit

  • Hammer/vice (for bending the mounting plate)

  • Metal bandsaw (for cutting the mounting plate and MAF sensor adapter)

    • Could also use a hacksaw

  • (Optional) 3D printer

Note: Most of the parts and tools we used can be found on our Amazon Storefront.

Step 1: Prepare the Apache 3800 Case

  1. Set the heater inside the case and mark the locations of the air intake and hot air output.

  2. Using a 3 inch hole saw, drill holes in each side of the case.

Step 2: Modify the Heater Mounting Bracket and Output Adapter

  1. Cut the excess flange off of the MAF sensor adapter.

    • This allows the flange to sit snugly against the top of the hole we drilled earlier (see 1st photo below).

  2. Align the adapter with the 3 inch output hole drilled earlier, mark bolt locations and drill holes for mounting.

  3. Bolt the MAF sensor adapter on the hot air output side.

    • a dryer vent hose easily attaches to the MAF sensor adapter plate using the 3” silicone hose coupler and included hose clamp.

  4. Cut the heater mounting plate to fit in the case and bend to create a 90 degree mount.

  5. Drill holes in the case for mounting the modified bracket.

  6. Bolt the heater into the case using the supplied hardware.

Step 3: Install the Exhaust

  1. Drill a 2 inch hole for the exhaust port on the same side of the case that the hot air output is on.

  2. Drill 3 mounting holes for the port flange.

  3. Cut the included exhaust pipe to length.

  4. (Optional) Use fiberglass heat sleeve to insulate the exhaust pipe.

  5. Using muffler sealer, install the exhaust pipe between the heater and the exhaust port using the included hose clamps.

Step 4: Install the Air Intake

  1. Drill a 1 inch hole for the air intake on the opposite side of the case from the exhaust.

  2. Mount the 3D printed adapter for the air intake hose (not included).

    • If you cannot 3D print the flanged hose mount, simply feed the air intake hose through the case.

  3. Cut the included air intake hose to length.

  4. Secure the air intake hose with the included hose clamps.

Step 5: Install the Fuel Pump and Hoses

  1. Drill a hole in the front of the case to mount the fuel pump bracket to.

  2. Install the fuel pump, ensuring proper orientation per manufacturer’s instructions.

  3. Connect output of fuel pump to input of the heater using 3/16 inch fuel hose.

  4. Connect fuel hose from the input of the fuel pump to the included fuel filter.

  5. Connect hose from the fuel filter to your fuel source.

    • In our case, we are using the included fuel pickup tube/stand pipe installed in the cap of our Rotopax container.

    • The fuel line can be connected and disconnected with a 4AN dry brake connector from Racetronix (QDS-0504A).

  6. Drill a notch in the lip of the case to pass the fuel line through when operating the heater.

Step 6: Install the Electrical

  1. Drill a hole for the 5 pin bulkhead connector just above the air intake port.

  2. Drill 4 small holes for the connector mounting screws.

  3. Cut the provided heater harness and solder both sides of the connector making sure all wires are correctly lined up.

    • 3 wires go to the remote

    • 2 wires go to a 12 volt power source

    • note: the Velit heater draws about 10 amps at startup. Keep this in mind when choosing a power source.

Step 7: Test the System

  1. With your fuel line connected to a gas tank, power the heater on.

  2. If your fuel line is longer than a few feet, you may have to prime the pump.

    • Navigate to the pump priming area of the menu and prime as needed.

  3. Once the fuel pump is primed, navigate to Power mode and hold the knob down for 2 seconds.

  4. As the heater starts up, check for leaks (both fuel and exhaust).

  5. Once you’re satisfied that the system is producing heat and there are no leaks you’re all set!

James & Kaity