Webasto Thermo Top C: The Complete Guide to This Popular Parking Heater
2026 Update: New Glow Plug Models and Improved Burner Availability
Since this guide was first published in March 2026, IntelliGenParts has added several new Thermo Top C part numbers to our inventory. We’ve also seen a significant increase in demand for the 1322644C glow pin (replacement for the discontinued 1322644B) and the 92335D burner chamber, which is now back in stock after a long shortage.
Updated 2026 Best Sellers (In Stock Now)
- 91370B Glowpin 12V — fits Webasto Air Top 3500/5000 ($14.90)
- 9005931B Glowpin 24V — for Thermo 90ST ($14.90)
- U4847 12V Water Pump — Thermo Top C/E/Z ($30)
- 92335D Heater Chamber Burner — Thermo Top C ($36)
- 9024802A Fuel Pump with Damper — universal fit ($19.98)
What is the Webasto Thermo Top C?
The Webasto Thermo Top C is one of the most popular diesel-fueled parking heaters used in RVs, trucks, boats, and off-grid cabins across North America and Europe. This guide covers everything you need to know to keep your Thermo Top C running reliably for 10+ years.
The Thermo Top C (also called TTC or TT-C) is a compact diesel-powered coolant heater manufactured by Webasto in Germany. It uses the vehicle’s fuel tank and circulates heated coolant through the engine block or cabin heater core, providing:
- Engine pre-heating in cold weather (down to -40°C)
- Cabin heating without idling the engine
- Pre-heated coolant for faster defrost
- Reduced engine wear and fuel consumption
The TTC has been in continuous production since the 1990s and is fitted as OEM equipment by Mercedes-Benz, Volkswagen, Ford, and many RV converters in North America.
Common Thermo Top C Models & Part Numbers
| Model | Voltage | Power Output | Common Use |
|---|---|---|---|
| Thermo Top C | 12V | 5.2 kW | Cars, small RVs |
| Thermo Top C | 24V | 5.2 kW | Trucks, commercial vehicles |
| Thermo Top E | 12V / 24V | 4.4 kW | Cars, vans |
| Thermo Top Z | 12V / 24V | 3.5 kW | Smaller vehicles, marine |
The 5 Most-Replaced Thermo Top C Parts (2026 Data)
After supplying hundreds of service shops and individual RV owners, we’ve identified the components that fail most often:
1. Glow Pin / Glow Plug
Failure rate: Very high (1-3 years typical life)
Symptoms: Heater won’t start, fault code 12
OEM dealer: $40-60 | IntelliGenParts: $14.90 (60% off)
Cross-reference: 91370B, 9005931B, 82306B, 1322410A
2. Water Pump / Circulation Pump (U4847)
Failure rate: High (3-5 years)
Symptoms: Poor heat output, gurgling sounds
OEM dealer: $80-120 | IntelliGenParts: $30
Shop: U4847 12V | U4847 24V French version
3. Fuel Pump (9024802A)
Failure rate: Medium (4-6 years)
Symptoms: Hard starting, no fuel delivery, error code 11
OEM dealer: $50-80 | IntelliGenParts: $19.98
Shop: 9024802A with damper | 9024802A English version
4. Heater Chamber / Burner (92335D)
Failure rate: Low (8+ years) but serious when it fails
Symptoms: White smoke, fuel smell, carbon buildup
OEM dealer: $80-150 | IntelliGenParts: $36
Shop: 92335D Heater Chamber Burner
5. Flame Detector / Sensor
Failure rate: Medium (3-5 years)
Symptoms: Heater starts then shuts down after 30 seconds, error code 04
OEM dealer: $50-90 | IntelliGenParts: $14.90
Shop: 1322644C Glow Pin Sensor 24V | 1322407A Sensor
How to Diagnose Common Thermo Top C Error Codes
| Error Code | Meaning | Likely Fix |
|---|---|---|
| 02 | No flame detected | Replace flame detector + glow pin |
| 04 | Flame goes out during operation | Flame detector or fuel issue |
| 11 | Fuel pump failure | Replace fuel pump (9024802A) |
| 12 | Glow plug failure | Replace glow pin (91370B) |
| 14 | Overheat shutdown | Check water pump + coolant flow |
| 15 | Heater overheat sensor triggered | Check coolant level + water pump |
FAQ: Thermo Top C Common Questions
How long does a Thermo Top C last?
With proper maintenance, a Thermo Top C will last 10-15 years. Most failures are consumable parts (glow plug, fuel pump, water pump) rather than the main unit.
Can I run my Thermo Top C on biodiesel?
Webasto officially approves B7 (7% biodiesel) blends. B20 and higher blends require modified seals and are not recommended.
Why does my heater shut off after 30 seconds?
99% of the time this is a failed flame detector (part #1322407A) or glow pin. Both are $14.90 at IntelliGenParts and take 15 minutes to replace.
Where is the serial number on a Thermo Top C?
On the data plate on the side of the unit. Send us a photo via WhatsApp and we can identify the exact parts you need.
Shop Thermo Top C Parts
Browse our complete Webasto parking heater parts collection or contact our team for a wholesale quote. We ship from stock to Canada and the US in 7-12 business days.