Engine fans constantly running

[Alanlaing]

Hi, I have a 2012 SLK55 AMG which has in the last couple of days seemed to have developed an engine fan issue, it’s constantly running from as soon as I start the car until I turn it off, has anyone else had similar issues at all.

 

[RogerSausage]

Have you had the A/C switched on?

 

[Alanlaing]

Have you had the A/C switched on?

Yes it’s never off

 

[RogerSausage]

Yes it’s never off

The fans will run to move air over the condenser, are they running faster then usual then?

 

[Alanlaing]

Yes it never used to come on unless it was really hot but yesterday it was on from the when it started till I turned it off, probably an hour on and off over a few chores running about.

 

[MrGreedy]

Can you just double check, is it on immediately on engine start, on ignition position 2 but pre-start, or does it come on around 10 seconds after engine start (consitent small delay each start)?

 

[Alanlaing]

Can you just double check, is it on immediately on engine start, on ignition position 2 but pre-start, or does it come on around 10 seconds after engine start (consitent small delay each start)?

Yes that is exactly what it does. About a 10 second delay, then the fan comes on.

 

[MrGreedy]

Yes that is exactly what it does. About a 10 second delay, then the fan comes on.

Probably low aircon pressure or duff ac pressure sensor.

Or low battery or various electrical possibilities.

I personally would go for an aircon pressure test and regas as the first port of call for around £50.

I needed a new condenser on a 2011 Merc a year or two ago due to gas leaking too quickly. Which also turned into a new pressure sensor because it was corroded solid into the bottom of the condenser. I would expect to need a new condenser typically from around 10 years due to perforation due to corrosion.

 

[Alanlaing]

Thanks I’ll get it looked into

 

[Alanlaing]

A further development today, as it’s been a bit warmer I turned the air con down to cold (it’s always on but at about 17) and it wasn’t really blowing cold at all, could well be related to the engine fan issues.

 

[Alanlaing]

Report back from the garage, it’s the Aircon pressure switch and a couple of seals which have failed. Stick in a regas and it’s all good to go for around £200

 

[Alanlaing]

Picked the car up and everything is running absolutely fine so thanks for the pointers everybody