Webasto Thermo 90 Glow Pin and Sensor 1322644C 24V: Failure Symptoms, Replacement, and Where to Buy
*Published on the IntelliGenParts Blog. Reading time: ~9 minutes.*
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## The 6 AM Call From the Driver
It is always the same call. A dispatcher in Edmonton. A long-haul trucker outside Saskatoon. A bus depot manager in Hamburg. The story is identical:
*”Three trucks won’t start this morning. All Webasto Thermo 90s, all 24-volt. Heater cycles, glow plug lights, but no combustion. Or it fires for 30 seconds and shuts down. Diagnostic tool shows F 00012 ‘ignition failure’ on two of them, F 00011 ‘flame sensor’ on the third. Dealer wants $90 a part and a week for delivery. I have loads to move.”*
The 24V Webasto Thermo 90 and 90ST are workhorse heaters — they are under the cabs of thousands of long-haul trucks, buses, and commercial vehicles across North America and Europe. They are also notorious for a specific failure pattern in cold weather: the combined glow pin and flame sensor assembly. OEM part number 1322644C. When it fails, the heater does not start. And the part is one of the more expensive dealer items.
This guide explains what the 1322644C does, why it fails, how to swap it in under 25 minutes, and how to make sure you are buying the right replacement.
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## What the 1322644C Actually Does
The 1322644C is unusual in the Webasto parts catalog because it combines two functions in a single field-replaceable assembly: the glow pin (ignition) and the flame sensor (combustion monitoring).
On most Webasto air heaters these are two separate parts — you can replace the glow pin without touching the flame sensor. On the Thermo 90 / 90ST and the DBW 2010 / 2016 (all 24V water heaters), the combustion chamber is too compact for separate components. The glow pin and the flame sensor share a single housing, a single mounting point, and a single set of leads. The part that fails is the assembly. The part you replace is the assembly.
### The Glow Pin Function
A 24V ceramic glow pin — silicon nitride element, Inconel 600 sheath — brings diesel to ignition temperature within 8-12 seconds of start-up. The ceramic element reaches 1,000°C+ in that window, which is hot enough to ignite the diesel-air mixture in the combustion chamber.
The glow pin is the most electrically stressed component in the heater. Every start cycle pushes 8-10 amps through a heating element that goes from room temperature to 1,000°C in 12 seconds. Over thousands of cycles, the element degrades.
### The Flame Sensor Function
A separate ionization electrode, integrated into the same housing, monitors the flame during operation. The ECU applies a small AC voltage to the electrode and measures the current flow through the ionized combustion gases. A healthy flame conducts a stable, low current. A failing or absent flame drops the current to zero. The ECU reads this signal continuously and aborts the cycle if the signal becomes unstable.
The flame sensor is the part that catches most problems: a bad burner, contaminated fuel, restricted combustion air, or a glow pin that lights but cannot sustain combustion.
### Why They Are Combined
The 24V Thermo 90 / 90ST combustion chamber is small and tightly packaged. Webasto’s engineers put the glow pin and the flame sensor in a single housing to save space and simplify the wiring harness. The trade-off is that a failure in either function takes out both, and a single replacement fixes both.
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## Why the 1322644C Fails
The 1322644C is a wear item. It works in a hostile environment: 1,000°C combustion temperatures, diesel vapor, vibration, and 8-10 amp electrical pulses every time the heater starts. The most common failure modes, in order of frequency:
### 1. Glow Pin Ceramic Cracking (45% of failures)
The silicon nitride ceramic element is brittle. It expands and contracts with every start cycle. After 1,500-2,500 cycles, micro-cracks develop in the ceramic. The element either opens (no current flow) or shorts to the sheath (uncontrolled current draw). Either way, the glow pin stops working.
### 2. Carbon Build-Up on the Glow Pin (25% of failures)
The glow pin sheath runs at 1,000°C in a sooty combustion environment. Carbon deposits build up on the surface, insulating it from the diesel. The pin takes longer to reach ignition temperature. Start times stretch. Eventually the pin cannot ignite reliably in the time the ECU allows.
### 3. Flame Sensor Electrode Erosion (20% of failures)
The ionization electrode is a small metal rod exposed to the combustion flame. Over thousands of hours, the tip erodes from the high-temperature ion bombardment. The electrode becomes too short or too thin to pick up a stable ionization signal. The ECU throws F 00011.
### 4. Wiring / Connector Failure (10% of failures)
The leads from the 1322644C to the ECU are short and exposed to vibration. The connectors can corrode, especially in marine and off-road applications. A bad connection mimics a bad assembly. Always inspect the connectors before replacing the part.
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## The 5 Symptoms You Will See
The 1322644C usually gives you warning before it fails completely. Watch for:
1. **Hard starting in cold weather** — start time stretches from 60 seconds to 3-5 minutes. In extreme cold, the heater fails to start at all.
2. **Error F 00012 (ignition failure)** — the ECU attempts to ignite, does not see a stable flame within the start window, and aborts.
3. **Error F 00011 (flame sensor fault)** — the flame sensor loses signal. The heater starts and then shuts down.
4. **Heater starts but shuts down after 2-3 minutes** — the classic “intermittent” failure pattern. Combustion begins, runs briefly, then the flame sensor loses signal.
5. **White smoke and raw diesel smell** — the glow pin is too weak to fully ignite the mixture. Diesel vapor escapes unburnt.
If you see any combination of these — especially F 00012 and F 00011 together — the 1322644C is the prime suspect. On a 24V Thermo 90 / 90ST, the combined code is diagnostic.
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## DIY Replacement Guide (8 Steps, ~20 Minutes)
> *Photo placeholders: [P1] tools laid out, [P2] old vs new assembly, [P3] glow pin and flame sensor leads, [P4] combustion chamber access, [P5] mounting nut, [P6] new assembly installed, [P7] wiring reconnected, [P8] successful cold start.*
### Tools You Need
– T20 Torx driver
– 10 mm open-end wrench (for the mounting nut)
– Flat-blade screwdriver
– Multimeter (for testing the old assembly)
– Nitrile gloves
– Clean lint-free rags
– Torque wrench (4 Nm range)
### ⚠️ Safety Warnings
– **Disconnect both battery terminals.** 24V commercial systems have high available current. A short during install is a serious fire risk.
– **Let the heater cool completely.** The combustion chamber and glow pin stay hot for up to 10 minutes after shut-down.
– **Cap the fuel line.** A diesel leak is a slip hazard and a fire risk.
– **Do not touch the new glow pin with bare fingers.** Skin oils cause hot spots and premature failure. Hold the assembly by the metal connector end only — use the gloves.
– **Do not over-torque the mounting nut.** The ceramic glow pin is brittle. Torque to 4 Nm — no more. Over-tightening cracks the element.
### Step 1 — Confirm the Failure Mode
Plug in a Webasto diagnostic tool (Thermo Test or compatible) and check the error log. F 00012 with F 00011 on a 24V Thermo 90 is diagnostic for the 1322644C. If you only see F 00012, the glow pin is the prime suspect; if you only see F 00011, the flame sensor may be failing. Either way, the assembly is replaced as a unit.
### Step 2 — Remove the Heater (Recommended)
Most Thermo 90 installations are under-floor on trucks or in engine bay compartments on buses. Removing the heater to a clean bench is the safest approach. Disconnect the fuel line, wiring harness, coolant hoses (for water heaters), and mounting bolts.
### Step 3 — Access the Glow Pin + Sensor
The 1322644C is mounted to the burner assembly, accessed by removing the combustion air intake cover (typically four T20 screws). Set the screws aside. The glow pin is the cylindrical part protruding into the combustion chamber. The flame sensor lead is a single wire on a separate terminal.
### Step 4 — Disconnect the Wiring
Disconnect the 2-pin glow plug connector — press the release tab, do not pull on the wire. Disconnect the single-pin flame sensor lead. Inspect both connectors for corrosion. If either is green or pitted, clean it with electrical contact cleaner before reassembly. A bad connector mimics a bad assembly.
### Step 5 — Test the Old Assembly (Optional but Recommended)
Use a multimeter to measure the resistance across the two glow plug terminals. A healthy 24V glow pin reads 1.5-3.0 ohms. Infinite resistance means the coil is open. Out-of-range resistance (less than 1 ohm or more than 5 ohms) means the element is degraded. The flame sensor is harder to test in the field — most mechanics replace the assembly as a unit.
> *[P2 photo placeholder: old assembly next to new, side-by-side. Old shows carbon build-up on the glow pin tip and slight electrode erosion.]*
### Step 6 — Remove the Old Assembly
Unscrew the 10 mm mounting nut holding the 1322644C to the burner. Withdraw the assembly straight out — do not bend it. The ceramic glow pin is brittle. Set the old assembly aside.
### Step 7 — Install the New 1322644C
Drop the new assembly into the mounting hole. Hand-tighten the mounting nut, then torque to 4 Nm (do not over-tighten). Reconnect the 2-pin glow plug connector until it clicks. Reconnect the single-pin flame sensor lead. Verify both connections are seated.
> *[P6 photo placeholder: new 1322644C seated in the mounting hole, mounting nut in place.]*
### Step 8 — Reassemble and Test
Reinstall the combustion air intake cover (four T20 screws, 2.5 Nm). Reinstall the heater in the vehicle. Reconnect the fuel line, coolant hoses, ducting, and battery. Power up and run a cold start.
A successful install shows clean combustion within 60-90 seconds, no error codes, stable heat output. Run for 15 minutes, then re-check the diagnostic log.
> *[P8 photo placeholder: control panel showing green LED, no error code, heat output.]*
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## Where to Buy — and What to Look For
The 1322644C is a popular 24V replacement. The challenge is sorting the OEM-equivalent suppliers from the cheap-cop crowd. Here is what to look for:
### What Matters
– **Ceramic silicon nitride glow pin.** Cheaper replacements use a metal-coil glow pin that burns out in 800 hours instead of 2,500.
– **Inconel 600 sheath.** Standard nickel sheath burns through at 700°C; Inconel holds to 1,000°C+.
– **Integrated flame sensor.** The 1322644C must be a single assembly. If a supplier is selling the glow pin and the flame sensor as two parts, it is not the right replacement.
– **2-pin glow plug + 1-pin flame sensor connector.** The original uses separate connectors for the two functions. A combined 3-pin connector is a copy.
– **12-month warranty minimum.** A supplier that will not stand behind the part for a year is telling you something.
### Red Flags
– “Universal glow pin for Webasto” — be specific or be suspicious.
– Price below $15 — at that point you are looking at a metal-coil copy that will not last a winter.
– No specification sheet, no material declaration, no test data.
– No returns on electrical parts.
### Why IntelliGenParts
– $25-40 retail, wholesale tier for workshops.
– 12-month warranty, no restocking fees.
– Ceramic silicon nitride glow pin, Inconel 600 sheath.
– Same-day shipping from EU and North American warehouses.
– Bilingual technical support (English / German).
– ISO/TS 16949 manufacturing.
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## Cost Comparison: Dealer vs Aftermarket vs IntelliGenParts
| Source | Part Price | Shipping | Lead Time | Warranty | Total Year-1 Cost |
|—|—|—|—|—|—|
| Webasto Dealer | $70-100 | $20-40 | 2-4 weeks | 12 months | $90-140 |
| Amazon / eBay (no-name) | $15-30 | Free-15 | 3-7 days | 30-90 days | $60-180 (re-install labor if it fails) |
| IntelliGenParts (retail) | $25-40 | Free over $200 | 1-3 days | 12 months | $25-40 |
| IntelliGenParts (wholesale 20+) | $18 | Free | 1-3 days | 12 months | $18 |
The math is straightforward. The dealer is the most expensive option by a factor of three. The cheap Amazon option is false economy if it fails in three months. IntelliGenParts sits in the middle on price and at the top on warranty and support.
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## Frequently Asked Questions
### How long does a 1322644C last?
2,000-3,000 operating hours under normal conditions. In a commercial truck running the heater 1-2 hours per shift, that is 3-5 years. Long-haul trucks running the heater overnight will see shorter intervals.
### Can I replace just the glow pin or just the flame sensor?
No. The 1322644C is a single combined assembly. The glow pin and flame sensor share a housing and a mounting point. You replace them together.
### What is the difference between 1322644A, 1322644B, and 1322644C?
The A, B, and C suffixes are minor revisions. The C suffix is the current production version and is fully backward-compatible with all earlier revisions. The connector pinout and mounting are unchanged.
### My heater has F 00012 but not F 00011. Is the glow pin the only problem?
Probably the glow pin, but on a Thermo 90 / 90ST the assembly is replaced as a unit. If the glow pin has failed, the flame sensor is not far behind. Replace the whole 1322644C.
### Can I install a 12V version in my 24V system?
No. The 12V and 24V glow pins have different coil resistance (0.3-0.6 ohms for 12V vs 1.5-3.0 ohms for 24V). Using a 12V pin on a 24V system will cause the coil to burn out in minutes. We stock a 12V variant — check the catalog or email us.
### Will this fit a DBW 2010?
Yes. The DBW 2010 and DBW 2016 share the same 1322644C glow pin + sensor assembly. The connector and mounting are identical.
### What is the typical failure pattern in extreme cold?
The glow pin takes longer to reach ignition temperature. The ECU’s start window is fixed (typically 90-120 seconds). When the glow pin cannot ignite within that window, the ECU throws F 00012. In cold weather, the failure happens faster because the diesel is thicker, the combustion chamber is colder, and the glow pin is already degraded.
### Where can I get technical support if I get stuck?
Email **raven@intelligenparts.cn** with photos of the install and a description of the issue. Our technical team replies within one business day. For fleet and wholesale customers, we also offer video call consultation.
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## The Bottom Line
If your 24V Webasto Thermo 90, 90ST, or DBW 2010 / 2016 is throwing F 00012 or F 00011 in cold weather, the glow pin + sensor assembly is the most likely cause. A replacement 1322644C from IntelliGenParts costs $25-40, installs in 20 minutes, and comes with a 12-month warranty. Total self-install cost: under $50. Total dealer-install cost: over $150.
Stock the part. Train your mechanics. Stop sending drivers home in the cold.
— *The IntelliGenParts Team*