C350e radiator fan running constantly

[miles_trooper]

Hi, I have had a 2016 C350e for just under a month, it's been fine so far but since the hot weather last week (may be coincidence) it seems to have a problem where the cooling fan runs near constantly at full speed. It does this almost immediately from starting the car, even before the petrol engine has started. It slows down somewhat when you are stationary but picks up again as soon as you start moving. It stops as soon as you turn the car off though, and I haven't heard it running when it's off.

There are no errors or warnings shown, and the engine/coolant temp in the center of the dash suggests the engine is not overheating - it gets up to about 90 degrees when the engine is running, but no more - and the fan runs even when the engine is cold eg I've run on battery only from start.

I'm unsure if the cooling system is also used to help cool the battery/hybrid motor as well though, or whether the temperature on the dash is for the engine or the coolant temp and whether it would include any heat produced by the hybrid system.

The only other thing I've noticed is that the air con (which worked happily in the hot weather last week) no longer seems to produce decently cold air.

Any ideas what this could be?

And if anyone has any suggestions for a decent Mercedes independant in central Bedfordshire, that would be great! I tried Millenium Mercedes in Bedford, but they can't work on Hybrids.

 

[mioba]

Hybrids is relatively new tech and the know how is with the dealers or with good indies who have access to MB databases otherwise it takes years for the info to trickle down.
Dealer could be best bet.

 

[FiveAlive]

Adding together the observations (cooling fan running constantly, air con not as good as it was), could it be a fault in the air con? The cooling fan can be turned on to draw air through the air con condenser in front of the radiator, so they might be related. As a quick test, try turning the air con off and see if the cooling fan stops.

 

[miles_trooper]

Hybrids is relatively new tech and the know how is with the dealers or with good indies

@mioba Yeah that's why I was hoping to find a good indie, my experience of Merc dealers pre-sale was so woeful I have no interest in giving them my money unless I absolutely have to. I guess for a car that's well out of warranty I was surprised though that an indie wouldn't have had a little exposure to them but hey. They said something about not being certified so maybe that's an additional cost or something.

Adding together the observations (cooling fan running constantly, air con not as good as it was), could it be a fault in the air con?

@FiveAlive that's a good shout. I had seen the secondary unit in front of the main radiator but hadn't twigged that was for the air con. I did try A/C on and off while driving around but will have another look at it this evening and maybe switch off climate completely and see what happens. Maybe it's just lost gas and that's that cause I don't know. My last car (Land Rover) had a habit of rusting through air con pipes and losing all the coolant, but I'd hoped a newer car might not suffer that yet.

 

[mioba]

Air con gas level could be low, or a leak in the system which will be picked up by a decent ac place as they have to evacuate and hold under negative pressure prior to refill.
AC refills are good usually every 6-8 years. Keep the system on all the time.

 

[miles_trooper]

@FiveAlive I tried turning off the AC and leaving the climate control on, and also tried turning the climate control off altogether. Neither seem to make any difference to the running of the radiator fan. The only thing that seems to change it is whether I'm driving or not.
Stationary = fan runs at medium speed.
Driving slowly around town = fan speed increases
Driving faster eg 40mph+ = fan goes full tilt (but it slows pretty much straightaway when the driving speed reduces)

I had to do an emergency run to hospital the other evening for my daughter (furthest I have driven the car since it started happening, about 60miles round trip). I kept the engine temp on the dash the whole time and it never went above 90 degrees, and no warnings come up on the dash, so I'm pretty sure this has nothing to do with engine temp. Hoping it's either an air con leak or a dodgy sensor that isn't too much to replace.

@mioba thanks for the info on air con, that's helpful to know.

I've booked into an independent merc garage a bit further away from me that can look at it next week (Autoclass in Milton Keynes). On the phone, they also suggested air con would be the first place they looked and though it's a trek, they can give me a courtesy car. Much more helpful than the Merc dealer I spoke to who couldn't book me in for another month, wouldn't have a courtesy car and would charge more than double the hourly rate despite offering to discount it for being an 'older' car

I'll see what happens next week and try to report back.

 

[LostKiwi]

Low air conditioning gas pressure can cause some cars to have the fan run continuously (my 129 does this).
Get the A/C checked.

 

[MrTash]

Hi, I have had a 2016 C350e for just under a month, it's been fine so far but since the hot weather last week (may be coincidence) it seems to have a problem where the cooling fan runs near constantly at full speed. It does this almost immediately from starting the car, even before the petrol engine has started. It slows down somewhat when you are stationary but picks up again as soon as you start moving. It stops as soon as you turn the car off though, and I haven't heard it running when it's off.

There are no errors or warnings shown, and the engine/coolant temp in the center of the dash suggests the engine is not overheating - it gets up to about 90 degrees when the engine is running, but no more - and the fan runs even when the engine is cold eg I've run on battery only from start.

I'm unsure if the cooling system is also used to help cool the battery/hybrid motor as well though, or whether the temperature on the dash is for the engine or the coolant temp and whether it would include any heat produced by the hybrid system.

The only other thing I've noticed is that the air con (which worked happily in the hot weather last week) no longer seems to produce decently cold air.

Any ideas what this could be?

And if anyone has any suggestions for a decent Mercedes independant in central Bedfordshire, that would be great! I tried Millenium Mercedes in Bedford, but they can't work on Hybrids.

Sounds like it could be an Air Con issue as I had much the same with my C220 a couple of months ago although in my case my control unit died as it's linked to the radiator fan system and started to run at high speed as soon as the car was started, from what my Independent told me anything in the Aircon like leaks, etc would cause the fan to run like this so from what you are saying I'd say you may well have a leak or a loss or low level of gas in the system. Other than the unit it's self it could be the sensor also but I'm sure it's nothing that serious or expensive to sort out unlike in my case a brand new control unit would have cost me almost £500 but thank God for eBay managed to get one for £70 used.

 

[miles_trooper]

Thanks for your responses all. The garage have looked at it today and diagnosed a faulty temperature/pressure sensor on the air con. This in turn is causing the system to think it's overheating and forcing the radiator fan to run all the time. They are quoting ~£240 to replace it, including diagnosis, labour etc. Fingers crossed that will sort it, I'll find out later today I guess!

For anyone that is interested and like I was, searching for a decent Mercedes independant... I'm pleased so far with how Auto Class in Milton Keynes have handled this, especially dealing with the 3rd party warranty company who have been useless at responding to emails or phone calls to try and get the work approved.