Falling_Penguin
New Member
Hi all,
I’m looking for some informed guidance on a Webasto Thermo Top C / E diesel wet system (UK install).
Background / history
The previous owner removed the original Webasto control module (timer face) because he found the maximum run time irritating (around an hour).
In its place, a simple on/off switch was wired in.
With this switch fitted, the heater did previously run, and I clearly remember the fuel dosing pump clicking ~4–5 times per second during start-up, so I’m confident the switch wiring can command a start.
Current symptoms
On start command:
Combustion air fan spins up in stages (initial spin, higher speed, then winds down)
Heater body gets warm (presumably glow pin pre-heat)
Fuel metering pump does NOT click at all.
No obvious combustion (no sustained run, no exhaust smell).
The heater then aborts the start sequence.
Fuel system context
Previously, when checking the fuel supply, I found the tank standpipe / pick-up was barely passing fuel. I cleaned this out and restored fuel flow, and got the heater working again.
To eliminate the possibility of fuel starvation, I am:
...Replacing the tank standpipe
...Replacing the fuel supply line
...Replacing the inline fuel filter
Key questions / uncertainties
Control module vs lock-out
With the original Webasto control module removed, am I correct in thinking:
A simple on/off switch can start the heater, but cannot clear a fault lock-out if one has occurred?
If I buy a replacement Webasto timer/control module, would that:
Allow lock-out clearing from the module itself, or
...still require Webasto Thermo Test / diagnostics?
No pump clicking
Given that:
the heater runs fan + glow,
but the pump is completely silent,
does that point toward:
ECU suppressing pump output (soft/hard lock-out),
or an electrical issue to the pump,
rather than simple fuel restriction?
My current plan is:
Replace standpipe and fuel line/filter
Bench-test the fuel pump with a 12 V supply (for click test)
Restore a proper Webasto control module (timer)
Then look at diagnostics if needed
Does that sound sensible, or should diagnostics/control be restored before further hardware changes?
What I’m trying to avoid
Replacing parts blindly (especially the pump) if the real issue is:
control/ECU state, or
lack of a proper controller to reset faults.
Any experience-based advice from people familiar with Thermo Top C/E behaviour, especially around lock-out handling and control modules, would be much appreciated.
Thanks in advance,
Falling Penguin
I’m looking for some informed guidance on a Webasto Thermo Top C / E diesel wet system (UK install).
Background / history
The previous owner removed the original Webasto control module (timer face) because he found the maximum run time irritating (around an hour).
In its place, a simple on/off switch was wired in.
With this switch fitted, the heater did previously run, and I clearly remember the fuel dosing pump clicking ~4–5 times per second during start-up, so I’m confident the switch wiring can command a start.
Current symptoms
On start command:
Combustion air fan spins up in stages (initial spin, higher speed, then winds down)
Heater body gets warm (presumably glow pin pre-heat)
Fuel metering pump does NOT click at all.
No obvious combustion (no sustained run, no exhaust smell).
The heater then aborts the start sequence.
Fuel system context
Previously, when checking the fuel supply, I found the tank standpipe / pick-up was barely passing fuel. I cleaned this out and restored fuel flow, and got the heater working again.
To eliminate the possibility of fuel starvation, I am:
...Replacing the tank standpipe
...Replacing the fuel supply line
...Replacing the inline fuel filter
Key questions / uncertainties
Control module vs lock-out
With the original Webasto control module removed, am I correct in thinking:
A simple on/off switch can start the heater, but cannot clear a fault lock-out if one has occurred?
If I buy a replacement Webasto timer/control module, would that:
Allow lock-out clearing from the module itself, or
...still require Webasto Thermo Test / diagnostics?
No pump clicking
Given that:
the heater runs fan + glow,
but the pump is completely silent,
does that point toward:
ECU suppressing pump output (soft/hard lock-out),
or an electrical issue to the pump,
rather than simple fuel restriction?
My current plan is:
Replace standpipe and fuel line/filter
Bench-test the fuel pump with a 12 V supply (for click test)
Restore a proper Webasto control module (timer)
Then look at diagnostics if needed
Does that sound sensible, or should diagnostics/control be restored before further hardware changes?
What I’m trying to avoid
Replacing parts blindly (especially the pump) if the real issue is:
control/ECU state, or
lack of a proper controller to reset faults.
Any experience-based advice from people familiar with Thermo Top C/E behaviour, especially around lock-out handling and control modules, would be much appreciated.
Thanks in advance,
Falling Penguin