Eberspacher exhaust pitch changes while running

[Saltram31]

Been running the Eber DILC for 3 months without hiccups, but yesterday the exhaust started fluctuating in tone.(not the constant roar) There are no fault codes flashing up on the control unit and the warm air is constant through the vents. It occurrs after its been running for a while. Any ideas would be great.
TIA.

 

[Momac]

When the temperature set is achieved the controls adjust the heater accordingly.

 

[pcatterall]

Is the fluctuation duration short or long? If long then the previous response may apply as the heater does slow down or speed up to maintain temperature.
If its huffing and puffing with a short duration ( a few seconds rather than minutes) then look elsewhere. I do get that sometimes with heaters on test ( like a panting noise?) but often with no cause that I can find.
If you can feel or hear the pump clicking then see if this is changing or constant ( the pulse frequency should be in your handbook).
Sorry I cant help more.

 

[Saltram31]

Thanks for the replies. pcatterall you are spot on. It is short duration panting,as you desribe, which I only noticed yesterday.The pump frequency is constant. I'm thinking whether it requires a service.

 

[Saltram31]

Could it be fuel related? Blocked filter or water in fuel?

 

[owen-cox]

Could it be fuel related? Blocked filter or water in fuel?

i have seen this with dirt in the fuel the panting is usually in time with the pump and is due to non constant fuel flow. check the filter if fitted and also check the gauze on the inlet of the pump.

 

[Yngmar]

At full power, almost all the audible noise on my D5LC comes from the blower motor, rather than the combustion (I only hear that during startup). So pitch changes would indicate an electrical problem rather than a combustion one. Might just be a loose/corroded wire somewhere (they sure are prone to that, with their little automotive connectors everywhere). If it changes blower speed intentionally, it is accompanied by clicking of the relays on the circuit board on the heater (may not be the same on newer generation models) - and the metering fuel pump would tick slower to match.

 

[pcatterall]

Thanks for the replies. pcatterall you are spot on. It is short duration panting,as you desribe, which I only noticed yesterday.The pump frequency is constant. I'm thinking whether it requires a service.

I have observed this from time to time with different heaters on test. My bench set up is all good ( ie no pump or fuel supply or battery problems) it usually just 'goes away' so I have never been able to re-create it or get to the bottom of its occurrence.
If it only occurs from time to time and does not get worse or more frequent I would be inclined to ignore it!

 

[David2452]

Very common issue, usually simply cured by fitting a pulse damper. More sophisticated later heaters like Webasto Evo have pumps with a much smaller dosage but higher Htz which alleviates this. Problem is that earlier heaters, particularly Webasto had a pulse damper as standard so it didn’t matter but because it was plastic and therefor not usable on many installs it was removed from marine kits, Mikuni are the only maker that used a metal one usable on all installs.