Parking Heater Not Working? Troubleshooting Tips

Hello everyone!

I've had a Webasto ThermoTop auxiliary heater for about 2 years. It always worked perfectly - until last week. The heater no longer defrosted the windows after 30 minutes. I noticed that the radiator was also warm. I then replaced the thermostat.
Unfortunately, I've now discovered that the heating system itself isn't working correctly: It doesn't run continuously; instead, it shuts off several times during operation and makes the normal noises associated with shutting down. However, it then restarts again. In the meantime, the vehicle's ventilation system turns on for a few seconds multiple times – it should actually be running constantly above 30°C! After 30 minutes, the coolant is only lukewarm.

Has anyone ever had a similar problem? I installed the heating system myself and I had hoped to become an expert in heating systems . But maybe I need to reconsider that and go to the Webasto service center...

Thank you very much and best regards,
Till.

Okay, three scenarios come to mind:

1. Somewhere, the water flow is obstructed. The heating system is heating itself up to the shut-off temperature (85°) without overheating, and then enters a regulated pause.

2. The flame extinguishes due to insufficient fuel/air/etc. However, I believe the heating system only makes one attempt to restart in this case and then shuts down if the flame goes out again.

3. If you have a thermostat or a backflow preventer for your heating system, it might be stuck or malfunctioning.

If necessary, take it to a Webasto dealer (usually a Bosch service center) and have them read the error codes. There might be a clue there.


'I also had a Thermo Top in my previous car, which worked perfectly for 4 years. Then it was stored in a closet for 6 months, and now it's working again. I never had any problems with it, and it started up immediately after installation, despite the long storage period.'

'In the current vehicle, there's an Eberspächer heater installed. There were some issues with air bubbles, which caused the overheating protection to activate. After adjusting the position of the check valve, those problems were resolved, and the heater now works perfectly.'

grumble... as I'm just hearing (a grinding noise), PC fans are definitely not as reliable... hmph...

CU Gremlin.

Hello,
I'm almost certain there are air bubbles in the system, and the auxiliary heater is shutting off due to overheating. I have an Eberspächer auxiliary heater, and I'm experiencing the exact same problem right now!

Best regards,
Achim

@Achim:
How does the error manifest itself in your Eberspächer system?
Ich bilde mir ein das meine D5W SC nicht genügend heizt. Heute hab ich das Ding bei -10° 1 Stunde laufen lassen. Danach war es im Auto ~15° und der Motor war laut Anzeige bei 1/4. Der Wagen ist ein Passat 3B mit AFN. IsIs that normal?

best regards
Ronny.

Okay, so here's what happened with mine: the heating system starts, the burner runs at maximum, and then after 30 seconds, it shuts down unexpectedly. Also, you could hear the water pump running without any water flowing.
The cause was the check valve. Its orientation was approximately like this: __|_|__. The pipes leading to the heating system went upwards and then curved downwards towards the heating system. Although the entire assembly was below the waterline, air was collecting there. I rotated the valve (it's now oriented like this: TT) and the problem was solved.

Regarding heating performance: DW5SC, this morning the temperature was -12°C. Climatronic set to 25°C. After 45 minutes, the car is comfortably warm, and the water temperature shows approximately 65°C (which corresponds to a real temperature of 52-55°C). Check the thermostat; the radiator should be cold. If necessary, switch the ventilation to recirculation mode (if possible).

@avoso

'Overheating should not occur; if it does, the heating system will go into fault mode and will NOT restart automatically, but will need to be reset (turned off and on again). Warning: After 3 consecutive overheating events, the Eberspächer system will lock itself and require a diagnostic device to be unlocked (whomever implemented this should suffer greatly). '

CU Gremlin.

My Thermo Top once had a faulty coolant pump. The heater ran for so long that it became too hot and shut itself off. However, it could be turned on again later.


Go to a Bosch service center that *actually* knows about Webasto systems, not just pretends to. They can use diagnostics to accurately determine the problem.

Interesting, but I need to re-examine the diagnosis.
Is there a way to read the error memory directly from the Eberspächer heater, similar to how you would use VAG.COM with a car?
Or does this only work with a special diagnostic device from Eberspächer?

best regards
Ronny.

Diagnosis is a weak point.

There is a PC program for Webasto, but I don't have any plans for an interface to connect it .

'With Eberspächer, the only options are using their proprietary diagnostic device OR a 7-day timer. I have no idea why they don't use a standard timer or the TP5 remote for diagnostics... They even display 'Err' on the screen, and since the error code is already a numerical code... GRUMBLE... Especially since the diagnostic cable already goes to the timer.'

CU Gremlin.

Hello!

Thank you for the many suggestions. While the theory about an air bubble seems very logical (and would also explain why the ventilation sometimes turns on for a few seconds), the heating system has been working perfectly until now, and I only opened the cooling system after the defect occurred.

Außerdem startet die Heizung mehrmals wieder von alleine, d. h. der Brenner pfeift wieder laut. Zwischendurch ist dann ein lautes Brummen zu hören, dass ich aus dem Nachlauf kenne - ich dachte immer es ist die Kühlmittelpumpe, dann wäre sie ja noch i. O.

Is there anything stored in the error memory if the heating system doesn't go into fault lock mode?

Perhaps another idea? Otherwise, I'll have to take it to a Webasto service center.
Regards, Thank you.
Till.

Hi,

'I once had a similar issue. In that case, the water pump was defective. It only heated the water in the auxiliary heater, and through diffusion, the water around the auxiliary heater also became warm (potentially including the radiator). However, the warm water wasn't being circulated, so it shut down normally because the water in the heater had already reached 90 degrees.'

The loud humming sound you hear after the system shuts off is usually the combustion air blower, which pushes cold air into the combustion chamber. You can confirm this by holding your hand in front of the air intake; you should feel a draft of air.

If you have some electrical knowledge, try disconnecting the pump from the central heating system and connecting it directly to 12 volts. It should noticeably start pumping water.

Regards,
Privately, I've been a Thermotop C driver for three years.

@avoso

'Overheating should not occur; if it does, the heating system will go into fault mode and will NOT restart automatically, but will need to be reset (turned off and on again). Warning: After 3 consecutive overheating events, the Eberspächer system will lock itself and require a diagnostic device to be unlocked (whomever implemented this should suffer greatly). '

CU Gremlin

Okay, in my case, what helped back then (I have the 4.D4WSC installed) was removing and reinserting the 3 fuses in the engine compartment for the heating system. That silly 'release' function is just for safety, so that nothing else breaks due to the customer's constant attempts to start it. }

Okay, so it worked perfectly in my Passat. But now, after almost 6.5 years, I think the heater is broken. It used to heat up to around 70°C. And even on the lowest setting, the interior is still quite warm.

Unfortunately, the car has been losing coolant for about a week, and it's displaying the 'F31' error code every time the engine is started.
'Does anyone have an explanation for this, or has anyone else experienced water loss? I'm starting to consider switching to a competitor, because mine initially had 7 faulty glow plugs and a broken control unit (after 1.5 years), but since then, it's been working fine... so far.'

So far.

Greetings to everyone.

Unfortunately, the car has been losing coolant for about a week, and it's displaying the 'F31' error code every time the engine is started.
'Does anyone have an explanation for this, or has anyone else experienced water loss? I'm starting to consider switching to a competitor, because mine initially had 7 faulty glow plugs and a broken control unit (after just 1.5 years), but since then, it's been working fine... until now.'


Okay, so '031' officially means: 'Interruption of combustion air blower motor.'

Solution: Check the wiring leading to the combustion air motor (electric motor) for continuity; if necessary, replace the electric motor.

Unfortunately, the car has been losing coolant for about a week, and it's displaying the 'F31' error code every time the engine is started.
'Does anyone have an explanation for this, or has anyone else experienced water loss? I'm starting to consider switching to a competitor, because mine initially had 7 faulty glow plugs and a broken control unit (after just 1.5 years), but since then, it's been working fine... until now.'


Since I can only guess that it's an Eberspächer product:

look: http://www.espar.com under technical manuals.

CU Gremlin.