Webasto Thermo Top C vs Thermo Pro 90: Which One Do You Need? (2026 Comparison)
Webasto Thermo Top C vs Thermo Pro 90: Which One Do You Need? (2026 Comparison)
Last updated: August 2026 • Reading time: 8 minutes
Choosing between the Webasto Thermo Top C and the Thermo Pro 90 is one of the most common decisions RV owners and truck operators face when replacing a failed parking heater. Both are excellent products from Webasto, but they target different use cases.
This guide from IntelliGenParts Co. will help you decide which one fits your needs — and where to source OEM-quality replacement parts at wholesale prices.
Quick Comparison Table
| Feature | Thermo Top C | Thermo Pro 90 |
|---|---|---|
| Heat output | 5.2 kW | 9.0 kW |
| Fuel consumption | 0.10-0.24 L/h | 0.18-1.10 L/h |
| Voltage options | 12V / 24V | 12V / 24V |
| Weight | 5.9 kg | 13.5 kg |
| Dimensions (L x W x H) | 310 x 145 x 175 mm | 595 x 245 x 220 mm |
| Best for | Cars, small RVs, vans | Large RVs, trucks, buses, boats |
| Typical price (new unit) | $800-1,200 | $2,000-3,000 |
| Common failure parts | Glow pin, water pump | Glow pin, fuel pump, control board |
When to Choose the Thermo Top C
The Thermo Top C is the right choice if you need to:
- Heat a small cabin (cars, vans, pickup truck campers, Class B RVs)
- Pre-warm an engine in moderately cold weather (down to -30°C)
- Save space and weight (5.9 kg vs 13.5 kg for the Pro 90)
- Save on fuel (consumes 0.10-0.24 L/h vs 0.18-1.10 L/h)
- Replace a failed OEM unit in a passenger vehicle (Mercedes Sprinter, VW Transporter, Ford Transit)
Top Thermo Top C Parts (In Stock at IntelliGenParts)
- 91370B Glowpin 12V — $14.90
- 9005931B Glowpin 24V — $14.90
- U4847 12V Water Pump — $30
- 92335D Heater Chamber Burner — $36
- 9024802A Fuel Pump with Damper — $19.98
When to Choose the Thermo Pro 90
The Thermo Pro 90 is the right choice if you need to:
- Heat a large cabin (Class A/C RVs, buses, boats, expedition vehicles)
- Pre-warm a heavy-duty engine in extreme cold (down to -40°C and below)
- Run the heater for extended periods (6+ hours continuously)
- Heat both cabin and engine simultaneously
- Replace a failed unit in commercial trucks (Volvo, Scania, MAN)
Key Mechanical Differences
While both heaters look similar in concept, they differ significantly in design:
Combustion System
The Thermo Pro 90 uses a larger burner chamber (similar to 92335D for the TTC) that requires more fuel and air per cycle. This is why the Pro 90 is roughly 2.3x heavier than the TTC.
Water Pump
The Thermo Top C uses the smaller U4847 water pump, while the Pro 90 uses the larger U4840 or U4850 circulation pump. Both are stocked at IntelliGenParts.
Glow Plug
Both units use similar 12V/24V glow plugs, but the specific part numbers differ:
- Thermo Top C: 91370B, 9005931B, 1322644C, 1322410A, 1322415A
- Thermo Pro 90: 9021593B, 1322644C, 9005931B (shared with TTC)
Control Board
The Thermo Pro 90 has a more sophisticated control board with diagnostic display. The Thermo Top C uses a simpler ECU that often just blinks fault codes via LED.
Cost of Ownership Comparison (5-Year)
| Item | Thermo Top C | Thermo Pro 90 |
|---|---|---|
| Heater unit (new) | $1,000 | $2,500 |
| Glow plug replacements (3x) | $45 | $60 |
| Water pump (1x) | $30 | $80 |
| Fuel pump (1x) | $20 | $45 |
| Burner (1x) | $36 | $120 |
| 5-year fuel cost (1h/day) | $365 | $1,200 |
| 5-year total | $1,496 | $4,005 |
Prices based on IntelliGenParts wholesale rates. OEM dealer prices would be 60-80% higher.
Can I Convert a TTC to a Pro 90?
No. The mounting points, fuel system, exhaust, and wiring harness are all different. You cannot upgrade a Thermo Top C to a Thermo Pro 90 in place. If you need more heat output, you must replace the entire unit.
Can I Use the Same Parts?
Some parts are shared (glow plugs, certain gaskets), but most are not interchangeable. Always check the part number against your specific model before ordering. Send us a photo of your data plate and we’ll identify the correct parts for you.
FAQ
Is the Thermo Pro 90 worth the extra cost?
Only if you need the higher heat output. For most passenger vehicles and small RVs, the Thermo Top C is more than adequate and significantly cheaper to run.
Can I install a Thermo Top C in a large Class A motorhome?
Technically yes, but it will struggle to heat a large cabin in extreme cold. Most Class A motorhomes use the Thermo Pro 90 or even larger Webasto units (DBW 2010/2020).
Which one is more reliable?
Both are extremely reliable when maintained. The Thermo Top C is simpler and has fewer parts to fail. The Thermo Pro 90 has more advanced features but slightly more complex electronics.
Shop Parts
Browse our complete Webasto parts collection or contact us for a wholesale quote on bulk orders.
FAQ
What is the main difference between Thermo Top C and Pro 90?
Heat output: TTC is 5.2 kW, Pro 90 is 9.0 kW. Pro 90 weighs 13.5 kg vs 5.9 kg for TTC. Pro 90 is for large RVs/trucks; TTC is for cars/vans/small RVs.
Can I use the same parts in both heaters?
Some parts are shared (certain glow plugs, gaskets) but most are different. Always check part numbers against your specific model before ordering.
Which is more fuel-efficient?
Thermo Top C: 0.10-0.24 L/h. Pro 90: 0.18-1.10 L/h. The TTC uses less fuel because it produces less heat.
Is the Pro 90 worth the extra cost?
Only if you need the higher heat output for a large cabin or extreme cold. For most passenger vehicles and small RVs, the TTC is more adequate and significantly cheaper to run.