Your diesel heater spins up, maybe puffs some smoke, then shuts down after two attempts. Here is the exact elimination sequence our factory service engineers use — work top to bottom, and you will find the culprit in about 10 minutes. (Seeing an error code on the controller? Jump straight to the complete error-code guide.)

⚠️ Work with the heater off and cooled down. Exhaust must always terminate outside the vehicle.

Watch: what a correct manual start looks like

Compare your heater against this normal start on the ComfortStart controller — 35 seconds.

Step 1 — Power: does anything happen at all?

Nothing on the controller? Check the fuse in the power harness, power to the control unit, and every connector for corrosion. 12V systems must read above 10V under load (24V: above 20V) — a tired battery is the #1 cause of winter no-starts. Voltage drop across the harness must not exceed 1V.

Step 2 — Fuel: is the pump clicking?

The fuel metering pump should tick rhythmically during the start phase. No clicking? Check its connector and wiring, check if the pump is frozen, and check for a blocked fuel line. First start of the season or after running dry: the line must re-prime — run two or three start cycles to bleed air, and check the line for air bubbles at every joint.

Step 3 — Air paths: intake and exhaust clear?

Two start attempts with no exhaust smoke at all usually means no fuel OR blocked pipes. Check the exhaust for ice (reroute if it forms a U where condensation freezes), and the combustion air intake for mud, snow or insect nests. Keep 300 mm clear below the exhaust outlet.

Step 4 — Smoke but no fire: glow pin

Smoke means fuel is arriving but not igniting — that points at the glow pin. Measure its resistance at room temperature: 12V air heater 0.42–0.7 Ω, 24V 1.2–2.0 Ω (coolant-heater glow pins differ: 12V 0.4–0.6 Ω). Out of range, or heavy carbon on the pin? Clean or replace it (genuine Kyocera glow pin). While it is out, clean the vent holes and combustion tube airways.

Step 5 — Fuel quantity test

Detach the fuel line at the heater, run it into a 100 ml graduated cylinder, bleed the system, then run the pump for exactly 5 minutes at full power and measure. Short of spec? Check pick-up pipe, filter and connections, then replace the filter or pump.

Step 6 — Ignites, then dies: flame sensing and beyond

If it lights but shuts down, the flame sensor is not seeing the flame: replace the glow pin first; if the pin measures fine, the ECU is the likely fault. Frequent stops while driving? Reroute intake/exhaust ends toward the rear of the vehicle. Wrong (summer) diesel gels in cold — confirm your fuel grade matches the temperature.

Still stuck?

Email kevin@hlnind.com with a photo of your setup and a video of the start attempt — our engineers answer personally, usually within a day.

About HLN — For 50+ years HLN has built diesel air and hydronic heaters as original equipment for major truck, bus and RV manufacturers (YuTong, SANY, XCMG and two Fortune-500 truck makers), with CE / ECE R122 / R10 certification. Shop heaters: Aerolyn 2kW, Aerolyn 4kW, Aquano 5K hydronic.