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Stan, Mercedes Technician
Category: Mercedes
Satisfied Customers: 3526
Experience:  Technical support engineer
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I have a C class 2.7 CDI saloon. I am told that the coolant

Customer Question

I have a C class 2.7 CDI saloon. I am told that the coolant water heater has gone short circuit and it has been disconnected while an new one is on order. The problem was the fault kept flattening the battery. The mechanic told me the feed goes straight to the heater.
Does this feed the heater via a relay ? which is energised on ignition and could the problem be the contacts on the relay are permanently closed i.e. knackered relay.
If I am correct where is the relay?
Submitted: 2 years ago.
Category: Mercedes
Expert:  Shantal-Mod replied 2 years ago.
Hello Steve,
I'm Shantal and I'm a moderator for this topic.
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Expert:  Stan replied 2 years ago.
Hello Steve,

the main positive cable on the heater unit is connected to the battery. There are no relays to switch off the power supply to it. The heater's internal electronics must stop the consumption of electricity when there is no signal from engine control unit.