Hi recently when stationary at junctions etc after a couple of seconds the Rev will pick up from 800ish to over 1000rpm  as if I am resting my foot on the accelerator and the fan kicks in even though the car hasn’t reached temperature ( sometimes the needle has barely moved) does anyone know what is causing this I’ve had the car 6 years and has only this last couple of weeks started doing it. 

Is it a diesel? Could be attempted dpf regen? 

 

Also is it a manual or an auto? 

Edited 16 December, 20196 yr by Gmac983

It happens if the battery volts are falling due to a load consisting, for example of lights, rear screen heater and other large current draws that are greater than the current being put in by the alternator at engine idle. The clever electronics then raises the revs to 1000 rpm to stop the battery over discharging.

It can be a sign that the capacity of the battery is low and heading towards need for replacement.  Mine did the same and failed a few weeks later.

 

As said above, fan coming on plus 1000rpm is a sign of  DPF regen taking place but you would know that as you must have been driving quite hard (non town traffic) before you stopped.

Hi i have an 08 1.9 pre dpf version. I understand that extra load will trigger the increased revs but I don’t understand why the fan is kicking in when the car hasn’t reached temperature 

Aircon refrigerant pressure can also trigger fan activity irrespective of engine coolant temperature, and refrigerant pressure will tend to increase when there's no airflow through the condenser due to car motion. Presumably your car has A/C and it is switched on when these observations are being made?

 

I don’t think it would be as I haven’t used it for a couple of years as kept leaking gas so just open a window in summer. I’ve checked water and water seems to be right. I have ran out of ideas was thinking about over riding it with a switch and just turning it off (isolate power)  until it reaches temp then turn it on and then the car will turn it on and off when necessary 

Faulty thermostat?

 

Increased RPM is usually down to the Climatronic calling for heat before the engine is up to temperature, but this wouldn't initiate the radiator fan.

 

Increased engine speed (generating heat) and the fan (cooling) at the same time is unusual.

 

The best thing to do here is to scan the car for fault codes. 

 

Edited 25 December, 20196 yr by silver1011

Will get it plugged in to friends (dodgy) Vcds what am I looking for when plugged in as there is no warning lights and temp guage is working normal. The only other time I’ve had a higher idle speed is when I’ve stalled it (tried setting off at speed in third or Fifth lol)

22 minutes ago, Sid123456789011 said:

 The only other time I’ve had a higher idle speed is when I’ve stalled it (tried setting off at speed in third or Fifth lol)

 

If your moving even slowly, and the clutch is disengaged, you will see the revs rise to about 1000rpm. It's a function of the anti-stall. Useful when reversing off the drive.

 

I know but once you dip the clutch again it drops back down with it being a diesel You don’t need to slip the clutch setting off (unless racing) still doesn’t explain what is happening now though

 

Did you find out what happened? I have the same problem