What happens: From time to time, the control unit recirc light will blink and the display reset itself to the value when the car was first turned on. When that happens, the blower motor turn off for a few seconds and then comes back on.

What I tested: there are no codes stors in the unit associated with this malfunction. If I unplug the instrument cluster, the probem goes away and the system with not "blink". When I reconnect it, the problem often goes away for a few hours or a few days.

Any advice on where to turn? I do not think it is the control unit itself since it never has that problem with the instrument cluster disconnected. It is also really strange that I do not get any codes.

Very, very frustrating.

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2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)

Have you checked the version coding of the unit?

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

i determined that P1 is 0, and P2 is 168. is is an october 97 E420.

__________________
2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)

P1 should be 71 or 72 & P2 should be 136

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

Really? I wonder why they are so off...

__________________
2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)

I changed the P1 and P2 codes as you recommended and still no difference. any other leads? I read somewhere maybe an engine speed sensor or is it car speed sensor? I am trying to figure out all the relevant sensors that are connected to the instrument cluster and they relayed to the N22. It seems any sensors connected straight to the N22 would trigger a fault and I am not getting any fault codes.

Your help is greatly appreciated. Would this be the kind of problem a good indy can figure out or should I go to the dealer?

__________________
2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)

Anyone up to the challenge?! Still not resolved.

__________________
2008 S550
2010 GLK350
1997 E420 (retired)
2005 CLK500 (retired)