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Discussion Starter #1
Now in my second Sprinter from the '99-05 era and I remember that when I hit the cab heater button on my last Sprinter it made a noise like Concord taking off, but sure enough the cab would get warm pretty darned quick.

On my current Sprinter the red light on the cab heater switch illuminates but there's no reassuring noise and, more imortantly right now, no cab heating. Not only that, but the engine takes a long, long, time to warm up, and in the current weather conditions the temp gauge barely moves off 40C, no matter how long the journey.

I'm guessing that the latter problem is a sticky thermostat, but having looked around various forums I'm stumped on the cab heater problem.

There is a large fused battery connector sitting unconnected in the engine compartment, but after I reconnected it the cab heater still didn't operate.

Does anyone have any recommendations on where to start fault finding?
 

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Discussion Starter #2
I managed to track down the UK agents of the cab heater manufacturer 'Eberspacher'. They have repair agents around the country, mainly in boat marinas as these heaters are used to provide cabin heating in small boats. Eberspacher gave me details of the nearest repair agent.

I went to Espar in Harleyford Marina, Marlow, Bucks. They took out the front n/s headlamp to get access to the cab heater and plugged in a diagnostic tool which identified a faulty flame sensor, which they replaced while I waited.

It all took about 2.5 hours to take out the headlamp, run the diagnostic, strip down the cab heater to replace the flame sensor and then refit everything.

Cost £135 for labour (very reasonable for the South-East of England), £46 for the flame sensor (seemed a bit pricey - I'm a gas engineer and your average boiler flame sensor is around 1/2 this), plus the dreaded VAT. Friendly service from Espar and they let me watch the entire procedure.

The cab vents now blow warm air about 3 minutes after starting the engine and the engine warms up much faster - now I just need to replace the engine thermostat!
 

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I have now replaced the thermostat, which has cured the cold running temperature problem completely.

When the cab heater is turned on the engine warms up to 40C in under two miles and the heating system is already blowing hot air by then.

I followed the procedure in the Peter Russek manual - the manual makes the job sound a lot easier than it is because of very tight wiring and piping over the top of the thermostat housing. This makes it very difficult to extract the bolts and then the housing even when the pipework etc., has been cleared away as far as cable and pipe lengths will allow.

In particular you need to remove the connector to the temperature sensor before you remove the thermostat housing, but curiously you have to put the connector back on before you refit the housing, or you won't have room to work it back on unless you have the tiny fingers of a 2 year old who has been using a grip developer since birth.

Instead of draining down the cooling system via the radiator or engine block, as the Russek manual suggests, I just put a bucket under the engine side bottom hose connection and removed the hose, which was a lot easier than trying to get to the drain points as the bottom hose jubilee clip screw was easily accessible from the top of the engine.

The job took about an hour altogether. I've seen it suggested elsewhere in other forums that the thermostat should be replaced every two years - not sure I'd want to do that!
 

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I've just changed my thermostat as well and it is quite fiddly but do-able. And your right about not draining down just undo the old stat and let the coolant drain into a bucket.

I'm running at 85degC now after two years at 50degC.

I wouldn't put too much effort into the eber heater as it warms up quick enough with a new stat, personal view.
 
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