How to Clean a Velit Gas or Diesel Air Heater

Before thinking about taking any steps for "cleaning" your Velit gas or diesel air heater, you should first address the cause for any soot buildup. What conditions have led to the heater having a buildup of soot? When all running conditions are right, these heaters can clean themselves and run for thousands and thousands of hours without any significant soot builup. Rather, it is sub-prime running conditions or a combination of factors that cause soot to buildup and if not addressed, will lead to an inoperable heater requiring complete disassembly.

What leads to soot buildup in a Velit Gas or Diesel heater?

Improper Fuel Delivery - This is the #1 cause of soot buildup, issues with fuel lines. 9 times out of 10, issues with our heaters are not with the internals of the heater assembly, and are actually, rather, to do with fuel lines and fuel delivery. This can be from out-of-spec installation fuel line routing/design, or it can develop over time from external factors such as heat, moisture, vibrations, or any other number of factors that can impact the fuel lines after installation.
That's it. It's almost ALWAYS issues with fuel delivery that causes soot buildup. There are a number of other smaller factors that can compound fuel delivery issues but in general if you are seeing black smoke out of the exhaust, or suspect soot buildup, you likely need to order some fuel line and consider remaking or altering your fuel delivery/fuel lines.

See this KB article for help with proper fuel line design and installation: Troubleshooting Fuel Line / Fuel Delivery Issues with Velit Gasoline / Diesel Air Heaters

When should you consider cleaning a Velit air heater?

If your heater is brand new, and after initial installation or shortly after, it's very unlikely your heater is sooted up, but could still be having fuel delivery issues.

An intermittent puff of black smoke out of the exhaust pipe every few seconds is not really cause for concern. Pulling the exhaust pipe and inspecting the exhaust port would give you a good idea of the soot amount. If there is 1-2mm of soot buildup on the inside of the exhaust outlet port, there might be a little soot, but if there is 3-5+ mm of soot inside the exhaust outlet, it's likely very sooted up and needs cleaning.

If you are seeing sustained heavy black smoke out of the exhaust, this is also a sign of a heavily sooted up heater.

Good news is soot does not hurt the heater, and it can be cleaned and made to run as good or better than new.

What is the "cleaning mode" on a Velit air heater

This mode does not actually clean the heater or the soot from the heater. All this mode does is heat the glow plug extra hot and runs the fan, to clean the glow plug. This can be useful in a flooded or over-primed situation to dry the glow plug to allow it to get red hot for ignition/combustion.

In general, "cleaning mode" is not something you will need to use at all for normal heater operation. Many Velit air heater users never use this mode. Furthermore, the glow plug actually performs this self-cleaning heating cycle when shutting down in cooldown mode.

How to clean soot from a Velit Air Heater

1. Preventative: Run the heater on Manual Mode

Run on manual mode high for 20+ minutes as a preventive measure against soot buildup. These heaters when fuel delivery is correct, will self-clean themselves by running on high. If heaters only ever run for a short time-5-10 minute cycles, on a lower fan/pump speed, they never really get the chance to "stretch their legs" and burn hot and blow out the dry soot dust.

2. Quick Clean Method with Intake/Carb Cleaner Spray

This method is proven to work, BUT, there are some considerations to be advised of before deciding to use the "quick clean" method with spray.

Again, if your heater is brand new, it's unlikely to be an issue with soot, rather, fuel delivery issues that need to be addressed for the heater to run correctly. And the below spray clean method can be somewhat messy, and should be avoided if unneccessary.

The spray method is typically in the scenarios where you need to get the heater running and are otherwise unable to perform a full disassembly and cleaning of the heater.

3. Proper disassembly and dry brush cleaning of Velit air heater

Important: Do not fully unscrew the Glow Plug SET SCREW! This screw only needs to be turned 180 degrees and loosened to remove the glow plug. If you remove this screw all the way you run the risk of losing the ball bearing.

If you suspect or know your heater is sooted up and want to properly clean it out then the way to do that is through disaseembly. Done this way, you can simply use a large dry brush to knock the soot out of the fins of the heat exchanger, which is messy, but you do not need to use any cleaner spray in the inside of the heat exchanger; rather, dry brush gets large deposit out sufficiently enough.

There are only about 10-11 screws for the disassembly of the entire heater. This can be intimidating, but actually, these heaters are very simple and this is relatively easy to do once you have the heater removed from the mounting plate.

Inside the combustion/burn chambers is where you want to make sure they are the most clean. The outer burn chamber can be dry-brushed and cleaned with paper towels. The inner combustion/burn chamber with the screen can be spray cleaned and allowed to dry with Intake/Carb cleaner available from auto parts stores. Be gentle with the screen behind the glow plug port.

Conclusion

If you are struggling with a sooted-up heater, it is very likely 100% in your control to clean and repair that heater if you need it functioning. It is possible through following the instructions in this article to have your heater working properly like new or better tonight.

Address fuel delivery issues. Clean the heater, recommend full disassembly if excess soot is suspected, and reassemble, and the heater should run like new. It is very rare for internal components to fail on these heaters in reality, from what we see in our support channels.

Again, 9 times out of 10, heater owners suspect something is wrong with the heater, but in reality 9 times out of 10, it's an issue with fuel delivery/installation that can be addressed and resolved within your own means.