W204 c63 fan comes on as soon as I start it up

[PorkRind]

Since having my mot the other day I noticed that the engine cooling fan comes on each time I start it up, from cold. This can't be right, I've checked the amg menu for temps and they're all low. Can anyone suggest what might be wrong. Whst part I need and how I can fit it myself?

Thanks.

[Ken555]

Same issue recently on our ML63

Faulty thermostat, stuck open, just over £100 for the housing & thermostat.

Took the chance to drain the cooling system and refill using Merc antifreeze.

[PorkRind]

Thanks for the reply. I'll get it booked in then. My rocker covers leaking a little oil so will get that done, too.

[PorkRind]

Ken555 said:

Same issue recently on our ML63

Faulty thermostat, stuck open, just over £100 for the housing & thermostat.

Took the chance to drain the cooling system and refill using Merc antifreeze.

Was this with a merc dealer or specialist, did it show up on their star diagnosis equipment btw? Thanks

[krisdelta]

I had the same issue, pressure sensor in a/c compressor. Turned around in a day by a main dealer. No codes showed on "normal" plug-in at local indy, but Merc found the issue and confirmed with tests before replacing the sensor. I can ping over exacting details if it helps.

[PorkRind]

krisdelta said:

I had the same issue, pressure sensor in a/c compressor. Turned around in a day by a main dealer. No codes showed on "normal" plug-in at local indy, but Merc found the issue and confirmed with tests before replacing the sensor. I can ping over exacting details if it helps.

That would be great, thanks.. Took it to merc in Bath (peasdown st john) theyve had the car all morning and nothing from them yet - although they said they'd be free first thing.. Interesting !

Think i've got another cracked wheel too, as nearside rear is showing a lower bar than the rest of the wheels after pumping it up to spec the other day. The fun never ends!

[krisdelta]

PorkRind said:

krisdelta said:

I had the same issue, pressure sensor in a/c compressor. Turned around in a day by a main dealer. No codes showed on "normal" plug-in at local indy, but Merc found the issue and confirmed with tests before replacing the sensor. I can ping over exacting details if it helps.

That would be great, thanks.. Took it to merc in Bath (peasdown st john) theyve had the car all morning and nothing from them yet - although they said they'd be free first thing.. Interesting !

Think i've got another cracked wheel too, as nearside rear is showing a lower bar than the rest of the wheels after pumping it up to spec the other day. The fun never ends!

So my invoice states: A/C Pressure sensor faulty, causing fan to run at high speed constantly. Item is 83177001 Refrigerant Pressure Sensor Remove / Replace. No code listed on invoice though.

[PorkRind]

krisdelta said:

So my invoice states: A/C Pressure sensor faulty, causing fan to run at high speed constantly. Item is 83177001 Refrigerant Pressure Sensor Remove / Replace. No code listed on invoice though.

Thanks very much, yes same was replaced, a sensor and a seal for the ac unit as it was leaking a bit, apparently. Cost £340 which isnt too bad i guess.

[krisdelta]

PorkRind said:

krisdelta said:

So my invoice states: A/C Pressure sensor faulty, causing fan to run at high speed constantly. Item is 83177001 Refrigerant Pressure Sensor Remove / Replace. No code listed on invoice though.

Thanks very much, yes same was replaced, a sensor and a seal for the ac unit as it was leaking a bit, apparently. Cost £340 which isnt too bad i guess.

It is what it is - and considering some of the frailties on other cars in this sector (RS4 gearboxes, M3 VANOS / Bearings), my C63 has dropped a single sensor in 48k miles, everything else has been consumables. They seem very well engineered overall and a very understressed engine too.

[PorkRind]

krisdelta said:

It is what it is - and considering some of the frailties on other cars in this sector (RS4 gearboxes, M3 VANOS / Bearings), my C63 has dropped a single sensor in 48k miles, everything else has been consumables. They seem very well engineered overall and a very understressed engine too.

Thats a very good point, mines doing fine at 50k and this is the only thing to go wrong. Its a keeper for sure. Thanks for your help.

[Ken555]

PorkRind said:

Was this with a merc dealer or specialist, did it show up on their star diagnosis equipment btw? Thanks

Showed up on a snap-on code reader as 0856 - Thermostat jams in open position - temperature rises too slowly P0128.

A reset cured the fan for a few starts then it came back.

Price was parts only, swapped it myself.