Electric heat booster

[Aleksey]

Team,

An issue has been identified with the electric heat booster. Attempts to locate a fuse have been unsuccessful, despite online references suggesting fuse 75. No such fuse exists in the system. Is it possible the unit is wired directly? Are there specific operational parameters required for activation? Some sources indicate functionality is limited to cold weather conditions with the engine and AC engaged.

Guidance on initial troubleshooting steps would be greatly appreciated.

 

[DSM10000]

Welcome.

Letting us know the model of the vehicle would help with an answer

 

[mersum1es]

Usually those are large fuses, found in pre fuse box or somewhere separate in engine bay depending on which car,
Edit: If its W204, pre fuse box 150A fuse number 103...

 

[Trickythemerc]

The heater booster is a common failure as is the auxilliary water pump. Both these parts have failed on my 220 CDI, the water pump I have done but held off on the heater booster for now.

 

[Petrol Pete]

Can someone explain what we are discussing here please ? Is it the residual heat function that uses the warm water in the engine block to heat the cabin with the engine off ?

 

[DSM10000]

Can someone explain what we are discussing here please ? Is it the residual heat function that uses the warm water in the engine block to heat the cabin with the engine off ?

No idea as the OP has not provided accurate information as yet.

 

[Supernoodle]

I would think we're talking about a PTC (positive temperature coefficient) electrical heater. It's used to heat the cabin air before the the engine is up to temperature.

 

[Trickythemerc]

I think it will be the pre heat to aid defrosting ? Big lump of a thing on the block that helps bring the coolant up to temp before the stat opens.

 

[Petrol Pete]

OP , please come back to us with a little more information , someone on here will be able to help

 

[mersum1es]

'Heater boosters' were electrical heaters for coolant in W210/W203, after that It was PTC heater in air duct. Fitted only diesel model. Yeah, bit low initial information... again.

 

[DSM10000]

'Heater boosters' were electrical heaters for coolant in W210/W203, after that It was PTC heater in air duct. Fitted only diesel model. Yeah, bit low initial information... again.

My W211 diesel had one. It produces warm air very quickly from start up.

 

[Aleksey]

W204 220 CDI 2008.

Fuse 103 is located in the pre-fuse box. Due to bad weather, I couldn't check the fuse.

What usually fails? The fuse or the electric heat booster?

 

[Petrol Pete]

Still none the wiser .

 

[Chrishazle]

I also would love to know more about this facility, as having a 2008 S204 C220Cdi for 12 years now I have never been aware of a pre-heat facility, just accept that a diesel takes a lot longer for the heater to give heat to the cabin compared to my 2008 3L petrol SLK!

 

[mersum1es]

Heater element has several (6?) PTC units, to heat cagbin faster, because modern diesels are slow to warm up and produce extra heat (like gasser engines do). If one of PTC fails, you will get a fault code. Dropping 1-2 units probably goes unnoticed, but if it fails totally, AND you are cold conditions like below -15C there is a difference. I have not heard W211/W204 heaters would have failed to short circuit --> huge current draw, like older W210/W203 coolant heater often did.

 

[Petrol Pete]

Getting there .....slowly....