I have a 2010 S550 4Matic that gives DTC B1395 for the circulation pump (A32/1m1) short circuit to positive or open circuit. I have disconnected the circulating pump that is below the windscreen wipers and the duo valve for the rear HVAC. The code remains. I was hoping it was going to be as simple as a parts replacement of the circulation pump or the duo valve, but I have found that is not the case (so far).

Any insight as to where to look?

 

most german cars have this idea to turn on the interior fan and circulate the engine's coolant for 30 mins - when the key has been taken out - "residual heating", REST in german naming - check buttons below the screen or on most BMWs

the issue is NO ONE ever knew, and NO ONE every used, and FEW ever needed it - so it was NEVER TURNED ON and thus the electric pump rusts and seizes after 6 to 9 years of inactivity - I don't know anyone who ever bothered to mend it

 

if u have rear AC individual controls one pump is behind the drivers front wheel inside the wheel arch - actually really easy job to play - the hoses are long enough you can sit and play - it $500 and the whole thing - the pump bit is pointless - the silly solenoids are needed to control the rear heating - mine went to stupid hot on one side - some even report it melts the trim (it gets that Hot !)

 

I have used the REST function. It does work for some ventilation and a moderate amount of heat or cooling. Both pumps do work. I disconnected the pumps and checked for the code if it was still present. Codes remained.

 

It does have 4-place HVAC. I have checked the function of the pump that is along the firewall and the one in the front right fender. Both are operational. From having the same set up in my W140, you are correct they can produce an amazing amount of heat!

 

in the first post you wrote (A32/1m1) which is the front blower motor

then have a photo of the same error on component (A31/1m1) which is the rear heater unit in the centre console

 

ha, found this today - might be interesting for others with older cars.... NOT that search found this post !

P-B-83.75/113 MAR08 - VIN A092227 to A119911. If the REST Button is nonfunctional, the Upper Control Panel (UCP) may have incorrect software installed. UCP will be flashed with latest available software.

 

Mine is a US spec 07 in that range...I've never tried the button.

 

I rebuilt the duovalve, located in the rear of the front right fender well. Found the motor that drives the impeller to be seized. No longer have this error code since replacing this part. Still do have a battery drain, DTC 1350, Component A2/12 (Rear window antenna amplifier module) or line to component has short circuit or open circuit.

 

Well how do you like that, my button doesn't work. Let my break it down logically. TL;DR: I probably need that UCP software update!!

- REST button doesn't light up or appear to do anything
- Through DAS, I tested all the buttons on the HVAC strip. They all registered as pressed when I press them EXCEPT for REST.
- I did have a 9027 code which the Launch whatever-it-is picked up but DAS required the dev section to see it. The Launch said 9027 is "No CAN Message Was Received From Control Unit A6(STH Or HB Heater Unit)." Well, my car doesn't even have module A6 because that is some crazy Siberian option to heat the cabin with fuel. DAS doesn't even admit this is a possible code. Initially I was thinking my UCP was coded wrong but now this is REALLY pointing to that bulletin!
- I thought, well, surely the pump is seized, then. So I manually activated it with DAS. Key on, engine off. Well, shockingly, it works. As soon as I commanded it on, I got hot heat from the vents. Turn it off, heat goes away after 10s or so.
- I have no pressing need for this feature, but I think it's neat and the HW is there, plus the system itself seems to work - just need to be able to turn it on properly.
- DAS seemed to know something but the link to WIS doesn't work (BenzNinja just said it doesn't work and I shouldn't expect it to work......). But I'd bet $10 that this would have told me about the bulletin, almost completing the diagnosis.



I'm going to see if I can work up enough courage to update the UCP SW offline with my BenzNinja setup. That bulletin is old enough that I am sure it is in there somewhere.

 

go careful - two pumps depending on vehicle spec

optional rear AC unit (takes up the cubby hole under the front arm rest - gives separate heating and ventilation controls in the back and gets 400g more AC gas for the car) this brings the second electric REST pump as described in post #9

the other pump you say you can enable in diagnostics for the std front REST button seems to be the hell clb0099 is having https://mbworld.org/forums/s-class-w...ml#post8912145

there is mad extras for customer customisation of the front AC unit - buried in dealer kit - or did someone miss code something (maybe on a SAM)

 

I have the standard dual zone HVAC. I'm going to see if I can pull that bulletin from WIS.

 

I cannot find the bulletin anywhere! Not DAS, WIS or the Internet...

 

WIS says that the coolant pump is energized to boost heater core flow during low engine RPM situations. I guess that explains why mine works fine, despite my UCP having the wrong software which I assume means "REST" has NEVER WORKED since the car was made, and it's 2024.

 

wrong or just there was an update it could have?

 

Well you said there is a doc P-B-83.75/113. I am sure there is but I can't find it. And I suspect that my UCP does need to be updated. I'm just saying if this is all true, that means my REST function has never worked since the car has been on the road 17 years ago. But my pump works just fine.

I wonder if it has something to do with the button layout. WIS shows a different button layout and REST is combined with the HVAC OFF button. Well on mine REST is a dedicated button, and so is OFF. Maybe that's why the button press doesn't even register in the UCP module, because it doesn't even understand what the REST button should even do. That would be insane.

 

mine is a separate one too - still not got round to trying it... when I stop the car I get out and lock it not stay there and play with buttons

 

Yeah same. I really have no use for it. But, I'd like it to work just because.

 

https://www.tsbsearch.com/Mercedes-B...83-75-P-045751

I "requested" it. I know it's going to say update UCP software but I just want the damn thing.

 

How about them apples?

Updated the SW myself. BenzNinja came in later to confirm I hadn't borked anything. It's a little scary given some weird messages in DAS, and of course the gauge cluster throws a total fit with every scary message the car can display cycling through.







Had to recode and all was well. "REST" now works. The pump runs, it keeps the interior warm. Neat. I think what's more impressive is this feature has probably NEVER worked in 17 years. Yet my pump works fine. I think the pump is used for more than just REST. Mine is clearly not seized, and it probably would be if it really never ran in 17 years.

 

please let us know if you think the heater systems is working as it was prior....

my car WAS running that later software - also did an AC module update, at the time I felt the cars overall HVAC went backwards... but these days suspect I should change that valve behind the engine.... mate with the CL500 (same engine) also sees like I am, each winter for last 3 years we needs to add more and more numbers to get the same level of heating inside

that said my car is on BOTH the UCP and AC module OEM software releases... the later AC update I thought messed everything up - but it gives more diagnostic info, (never bothered to see what it was) - maybe I'm dim - but most mercs you can see the AC gas level - but never found that on mine, using either iteration of software

.

 

ha ha, just realised.... my chassis number is inside that range !!!!! is it any wonder it never worked - best bit never tried the button when I did have the correct software in there....

so they made 27,648 cars and no owner in 3 years complained the "pointless" button doesn't work....


.

 

had a little look at the time line of the mess up they were making on the UCP heater button module
(A221 442 13 23, SW Version 05/26/00
(A221 442 20 23, SW-Stand 06/19/00
(A221 442 26 23, SW-Stand 07/02/00
(A221 902 11 02, SW-Stand 10/07/00

they just have no idea....

here what you had, and what they were trying BADLY to fix (for my car that was on the original release) and they still left it full of bugs - as you say on 27,000 vehicles for 17 years !!!!

Diagnostic service $18 03 FF 00 (Read_DTC_All_Supported), Diagnostic service $18 02 FF 00 (Read_DTC_All_Identified): Error codes now appear depending on the recognized/installed OBF/KBF/LDS variant. 5. If the Lin sleep process is interrupted at a certain point, the LIN driver first reinitializes itself. The LIN sleep process is then continued again and cyclic sending is ended. The time window in which this wake-up event must take place is approximately 15 us. Since the "LIN-SLEEP" status was deleted by the initialization, the LIN driver is not reinitialized when the CAN wake-up occurs again and the OBF no longer goes into power-down, but the CAN always does woken up and runs without any problems. Only by changing the SW (OBF wakes itself up during the 15us) was I able to create the same state that we had in the vehicle. 6. Wakeup LIN approx. 1.5s after Sleep Ackn. In an interval of 15ms, CAN means that the LIN is not woken up (the LIN wake-up pulse of 1ms width falls into a gap of 15ms where the CAN transceiver cannot process the wake-up pulse). --> HW issue, not yet solved. 7.Wake up after 1.5s after Sleep Ackn. leads to the entire EEProm being overwritten. Loss of variant coding. The variant for all OBFs is then set to 'Heated windshield and auxiliary heater' = 0x03 in Block8. Correction only possible via new writing to EEProm Block8. However, the error can occur again. Background: OBF only carries out partial initialization (processor registers are not reinitialized. SW 05/26/00 executes an endless loop here --> watchdog reset --> complete initialization. Application serial version Flash class for functional software with serial version. Application software CTRL_U 221 for Ä J 07/1

I GUESS by A221 442 26 23, SW-Stand 07/02/00 they thought they had sorted it as those code comments are deleted....

but then in the facelift version you just installed we see this

Bug fix: - Undervoltage of less than 5V and subsequent charging of the battery without disconnecting the poles can lead to a bus guard in the series version of the OBF. - Variant with additional heater button: REST button is now sent immediately when the bus wakes up.Application flash class for functional software. Parameter data Flash class for parameter data. Bootloader flash class for flashable bootloaders. OBFW221_10_07_00_00 Software for OBFs up to and including AEJ08_1: Bug fix: - Undervoltage of less than 5V and subsequent charging of the battery without disconnecting the poles can lead to a bus guard in the series version of the OBF.

 

umm

I wonder if this is STILL BROKEN IN THE LAST RELEASE U JUST ADDED and hence why my electric headed front screen doesn't work

I added the version you have TRYING to find obscure canbus bug (THEY STILL DON'T KNOW THEY HAVE) trying to find SOMETHING that would stop messing up the SAT NAV Fade


I'll have more to add on this fiasco next hard frost !!!

 

It's the same. I only updated UCP not any other HVAC stuff.

When it asked about coding, I selected everything to no. I think the choices are heated windshield (screen for you), stationary heater and heater booster. Everything seems to work. Do you happen to have the codes for these so I can double check?

The number I'm on doesn't quite match the latest you cited though.