Webasto Glow Plug Replacement: Step-by-Step Guide (2026)

Last updated: August 2026

The glow plug (also called glow pin) is the #1 failure part on the Webasto Thermo Top C. This guide from IntelliGenParts Co. walks you through the complete replacement procedure. With our $14.90 OEM-quality glow plugs, you can do this job in 15 minutes for 60% less than dealer prices.

When to Replace the Glow Plug

Replace your glow plug if you see any of these symptoms:

• Heater won’t start (LED flashes code 12)
• Heater starts but shuts down after 30 seconds (code 04 or 07)
• White smoke from exhaust on cold starts
• Heater takes 2-3 tries to start
• Annual maintenance (replace every 2 years preventively)

Tools You’ll Need

• 8mm socket wrench
• 10mm socket wrench
• Flathead screwdriver
• New glow plug (part numbers below)
• Clean rag
• Work light
• 15-20 minutes

Part Numbers & Compatibility

Not sure which one? Send us a photo of your data plate to raven@intelligenparts.cn or WhatsApp +86 13093623263.

Step-by-Step Replacement

Step 1: Safety First

• Turn off the heater (control panel or remote)
• Wait 15 minutes for the unit to cool down (it can be 200°C+ during operation)
• Disconnect the negative battery terminal
• Locate the heater (usually under passenger seat, in engine bay, or in trunk)

Step 2: Access the Glow Plug

The glow plug is located on the top of the combustion chamber, accessible from above. You may need to remove a cover or heat shield:

1. Remove any plastic cover on top of the heater (usually 2-3 screws)
2. Locate the cylindrical glow plug screwed into the combustion chamber
3. The plug has one wire connector on top

Step 3: Disconnect the Wire

• Gently pull the wire connector straight up (do not twist)
• If stuck, use a small flathead screwdriver to pry the tab
• Set the wire aside — it does not need to be removed from the heater

Step 4: Remove the Old Glow Plug

• Use an 8mm socket to unscrew the glow plug (turn counter-clockwise)
• It may be tight if the unit has been running hot — use steady pressure, not force
• Once loose, unscrew by hand the rest of the way
• Pull the old plug out — it will be black/sooty (this is normal)

Step 5: Inspect the Glow Plug

A failed glow plug typically shows one of these signs:

• Broken coil (visible gap in the heating element)
• Heavy carbon buildup on the tip
• Corroded electrical connector
• Melted or deformed housing

If the glow plug looks normal, the problem may be elsewhere (flame detector, fuel pump, control unit).

Step 6: Install the New Glow Plug

• Remove the new glow plug from packaging — do NOT touch the heating element with bare fingers (oils reduce lifespan)
• Screw in the new plug by hand (clockwise) until snug
• Use the 8mm socket to tighten — but do NOT over-tighten (max 8 Nm / 6 ft-lbs)
• Reconnect the wire connector (should click into place)

Step 7: Reassemble and Test

1. Replace any covers or heat shields
2. Reconnect the battery
3. Turn on the heater via control panel or remote
4. Watch for successful ignition (10-30 seconds)
5. Run for 15-20 minutes to verify proper operation

What to Do If the Heater Still Won’t Start

If replacing the glow plug doesn’t fix the issue, check these in order:

1. Flame detector (50% of the time) — also worn out, replace at the same time
2. Fuel pump (30% of the time) — check for diesel flow, replace if needed
3. Coolant level (10%) — heater may overheat without enough coolant
4. Wiring harness (5%) — check for corrosion at the connector
5. Control unit (5%, rare) — needs Webasto diagnostic tool

Pro tip: Always replace the flame detector and glow plug at the same time. They have similar lifespans, and replacing both saves you a second teardown in 6 months.

FAQ

How often should I replace the glow plug?

Every 2 years preventively, or when symptoms appear. The glow plug is a consumable like spark plugs in a car engine.

Can I clean the old glow plug instead of replacing it?

No. Once the heating coil is damaged, cleaning won’t restore it. Always replace.

Why are IntelliGenParts glow plugs so much cheaper than dealer?

We source directly from ISO 9001 certified manufacturers in China. The parts are form-fit-function identical to OEM but cost 40-60% less because we skip the dealer markup. All parts carry a 1-year warranty.

What if I install the wrong glow plug?

Wrong voltage (12V vs 24V) will cause immediate failure. Wrong part number for your specific model may not fit or may burn out prematurely. Always verify part number with photo of your data plate.

Need Help?

Send us a photo of your Thermo Top C data plate to raven@intelligenparts.cn or WhatsApp +86 13093623263. We’ll identify the correct glow plug and ship within 24 hours.

Browse all Webasto Thermo Top C parts at IntelliGenParts.

FAQ

How often should I replace a Webasto glow plug?

Every 2 years preventively, or when symptoms appear (won’t start, code 12, white smoke on cold starts). The glow plug is a consumable like spark plugs.

Can I clean a glow plug instead of replacing it?

No. Once the heating coil is damaged (broken, corroded, or heavily carbon-fouled), cleaning won’t restore it. Always replace.

What tools do I need to replace a glow plug?

Just an 8mm socket wrench, 10mm socket (for cover), flathead screwdriver, and a clean rag. The job takes 10-15 minutes.

What happens if I install the wrong glow plug?

Wrong voltage (12V vs 24V) will cause immediate failure. Wrong part number may not fit or burn out prematurely. Always verify part number with a photo of your data plate.