Vito 111cdi Radiator Fan Issue

[northdude]

Hi I'm having an issue with the front radiator fan. 20 seconds after engine start up the fan starts and runs at full power until the engine stops.
Ive plugged it in to various code readers and its not bringing up any faults.
Mercedes want £168 per hour for diagnostic so just seeing if anyone on here has any suggestions or should I just bite the bullet amd take it to them. Any info will be much appreciated.

 

[EmilysDad]

if you give an idea of where in the country you are, I'm sure that someone will be able to recommend a trusted independent Merc specialist that won't cost you an arm & a leg!

 

[northdude]

I know of one specialist near me but heard really bad things about it.
I'm in the North East UK.
Thanks

 

[Kev555]

look at live data on one of them code readers and see what your temp sensor is displaying at cold. Theres possibly one sensor on the radiator itself that controls the fan which might be faulty

 

[northdude]

look at live data on one of them code readers and see what your temp sensor is displaying at cold. Theres possibly one sensor on the radiator itself that controls the fan which might be faulty

Yes my reader has live data. Thanks I'll check that out.

 

[sonic]

You could always put a switch in on the live feed, then turn it on when it gets hot.

 

[northdude]

You could always put a switch in on the live feed, then turn it on when it gets hot.

Yeah that's always an option. If it comes down to something like ECU then I'll probably do that. I'm hoping it's something simple but from what I've read online the fan can be triggered by a whole list of faults. I'm hoping it is just the temp sensor.

 

[Kev555]

Sensors and wiring loom are the first place to start after that it can get technical.

 

[northdude]

Ive just got back after being away and plugged my reader in to check the live data. On start up the coolant temperature was reading 15 degrees C but the air intake reading was 65 degrees! The ambient temp outside is 7 degrees C. Could this air intake sensor be the cause of the fan issue? And if so which sensor would this be?
Thanks

 

[northdude]

Would this be the ambient air temperature sensor?

 

[Kev555]

Not sure if the air intake temp triggers the fan, although I thought I saw a post before that somebody had the same issue with fan and had a faulty MAF. They changed the MAF sensor as I think thats where the ECU gets the air intake temp but dont quote me on it. Dont remember if changing the MAF cured the fan issue. If the MAF is faulty it needs changed anyways. Buy a good quality recommended brand or a genuine merc one

 

[northdude]

Thanks I'll do some digging to confirm. I've got MAF cleaner so might try cleaning it tonight and seeing if that does anything. I'll start hunting for a new sensor in the meantime.

 

[M80]

Mercedes > Mercedes EPC Online > nemigaparts.com

Parts catalogs. Spare parts catalog Mercedes EPC Online. Mercedes.

nemigaparts.com

This might help point you toward the sensor.
Pretty sure there is the ambient temp sensor as part of the MAF, on the air filter intake.
There should be another temp sensor on the intercooler pipework.
I don't know how either might affect the fan.

I've no personal experience, but seem to remember reading that AC issues can cause the fan the run continually??

 

[northdude]

Yeah I'm not having an issue with the ambient air temp, those readings are fine. The ambient air sensor is located near the bumper from what I've read. There is no AC fitted on the van.
The coolant temperature readings are also normal so it's either the MAF or another hidden sensor. I'm going to pop in to MB now and ask some questions. Hopefully will clarify

 

[M80]

ambient air sensor is located near the bumper

True, my mistake.

 

[northdude]

So I've been to Mercedes and the guy said there's nothing on it that records the air intake temp! He said the fan will also do that if the DPF is blocked. Now im confused

 

[northdude]

So how am I getting a reading on my live feed for intake air temp

 

[M80]

Is there a sensor code,
you might look that up on Google.

 

[supernoodle]

I haven't seen a MAF that isn't a TMAF for a long time....disconnect it and if you get a fault code for the inlet temp you know the MB man was talking rubbish...

 

[northdude]

Good idea mate I'll do that tonight.