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The view in this photo appears to be the side where you made all the connections of the cables running to this part. Those cables would not be part of the part. The video grab you shared above appears to be after removing the plastic cover on this side where you might see all the internal connections including fuses and relays. Have you taken it apart to see what's on the inside?
At this point, you're probably doing the best thing by taking it to a mechanic. When I was reading those instructions and looking at all those connections, I was thinking I would hate to mess this one up.
The view in this photo appears to be the side where you made all the connections of the cables running to this part. Those cables would not be part of the part. The video grab you shared above appears to be after removing the plastic cover on this side where you might see all the internal connections including fuses and relays. Have you taken it apart to see what's on the inside?
At this point, you're probably doing the best thing by taking it to a mechanic. When I was reading those instructions and looking at all those connections, I was thinking I would hate to mess this one up.
I think I have the right part, which does have the openings for the cables to connect as you mentioned. The video screengrab that showed the bolt down fuses must be from another model mercedes. Either way, my car was just towed which is probably best considering I could have potentially made the situation worse. I'll be sure to post a follow up to what fixes the issue.
Car was towed to the dealer and their diagnostics confirmed it was the F32 pre-front fuse. Total cost damage is $650 + Tax, which is better than I thought.
Also, see the pics below. Even though my car would not go into neutral, the Mercedes certified tow company has a cool apparatus that's bolted onto the rotor/axle that unlocks the transmission somehow and allows it to be towed. The tire is then remounted on top fo this boot/apparatus.
Hey, your diagnosis was right. If only that part was easier to replace.
That attachment looks like a bearing so the tire can spin independent of the axle. I assume they installed in on both sides of the rear so the wheels can freespin.
Hey, your diagnosis was right. If only that part was easier to replace.
That attachment looks like a bearing so the tire can spin independent of the axle. I assume they installed in on both sides of the rear so the wheels can freespin.
No just on one side. He made it sound like he could have installed it on any wheel, front or back. Pretty cool!
Even though my car would not go into neutral, the Mercedes certified tow company has a cool apparatus that's bolted onto the rotor/axle that unlocks the transmission somehow and allows it to be towed. The tire is then remounted on top fo this boot/apparatus.
With all wheels down it makes a difference between RWD and AWD. If it is RWD then for sure the "free bearing " must be mounted on one of the rear wheel hubs. If it is a AWD car then you need one for each axle unless you don't mind wearing on that center differential lock disk.
But a short pull to a flat bed should not be a problem.
i replace the pre fuse box with a new one and all the trouble is gone now,after 1 year of stress and money spent with som merc specialists,my 2012 e class start normal every morning.
Thanks you all for this thread, I just had the exact issue, as strange as it is, with my 2010 E350. I had no doubt that this was going to be over a thousand dollar repair at the dealer.
With the help of this sharing of ideas I was able to purchase a new Prefuse box, install it, all the issues went away including not able to get it into gear. The step by step guide attached to this thread was spot on and gave me the confidence to attempt the repair.
For those who end up with the same symptoms, basically other than the car starting, nothing works or reports to be off line (read beginning of thread), all you have to do is go online, search using your VIN for Prefuse box, I got mine for less than $160, (my local dealer parts dept wanted $301), it is a self contain unit, all relays and fuses are not visible, but they are there.
Here is the part info for my VIN:Part NumberPart NamePriceQuantityTotal212-540-62-50-64Fuse Box$153.601$153.60 Subtotal: $153.60Shipping (Expedited): $13.37Total: $159.29
As I said earlier, the shop manual AR54.15-P-1330EW Remove/install front prefuse box, was detailed enough for me to attempt the replacement, but I will add that the instructions to: unlock fuse on Step 7 is misleading and cause a delay in the replacement. If you are going to do the same repair, the fuse indicated as # 3 in the picture simply pops straight off, using a screw driver I gently popped the connector off. No fancy push down then turn, just lift straight off and on to the new Prefuse box
the red arrow pointing to pyrofuse connector
Lift up in direction of arrow
Hope this helps someone else faced with the same issue
How to get a 4-matic onto a flatbed, when stuck in park
I couldn't believe it, the tow guy, removes my passenger side rear tire, places a u-shaped wooden block under my suspension to allow the rear hub to turn in reverse, while the 3 other tires rotate forward, allowing the car to be dragged up the flatbed ramp
After not using the car for a few days, the same problems returned...dealer arranged for a flatbed to pick up my car, took 5 hours over a few days, and two techs to trace the issue to the rear SAM unit. in my case the part # was 212-900-40-22.
Just got it back, so I hoping the issue is now completely solved.
I had the same issue on my W204 C250 CDI 2012 model and have replaced the pre fuse box which has resolved the issues.
The relay in the pre fuse box fails to close and therefore power is not supplied to the rear SAM which results in all of the fault lights, stuck in park and no power steering.
BTW, rather than get the car towed you can just provide 12V to the terminal on the pre-fuse box which then energises the rear SAM, everything will then function.
If you don't want to purchase the whole pre fuse unit, in my case part# A2075402750 you can open the unit and replace the relay part#A0035421819.
THANK YOU ALL SOOO MUCH!!! I've been dealing with this issue for over a year now!! It seems to come and go as it wants. I have torn my car up from testing all fuse boxes, digging through both SAMS, replacing the battery, the alternator, and all the while getting a voltage spike in the alternators harness from diagnostics. THIS HAS BEEN A NIGHTMARE!!! I live in Miami so when this happens Im literally stuck in a car with NO AC, cant roll down the windows, literally cooking in the car. It has had me stranded for many many hours, and it has literally been a living nightmare!!! I just ordered my prefuse box for my 08 W204 and CANT WAIT TO CHANGE IT OUT. I really hope this is the final piece for it has been too long and too much at times dealing with this. These issues seem exactly whats wrong, even with the fan going into turbo mode, this usually happens while the car is running and flickers on and off before just staying off leaving me trapped in a VERY HOT vehicle. I CANT THANK YOU GUYS ENOUGH!! MY YEAR HAS BEEN TURNED AROUND BECAUSE OF THIS POST!!! IM SOOO GRATEFUL AND CANT THANK YOU ENOUGH. I pray this is the fix, it sounds spot on though. THANK YOU ALL
^ There are some seriously good diagnosticians on this forum. I wouldn't be able to do half of what they recommend but I'm grateful as hell that they're here if I ever *do* have a problem.
So, same problem, I'm thinking to change the relay A0035421819. But what is its role ? I have a picture with my F32 prefuse box and I have 12V at 1, 2 and 3 connexion points. It is ok or not ? What should this relay cut or connect ? Thanks very much for your answers ! F32 prefuse box
Can somebody chech the voltage on the three connection at F32 box ? Everybody is talking about relay 30g not closing. I have all errors related to this (less then 7.5V, less then 8.5V and out of range tension) that sugest that I have to change the prefuse box. But I have 12 V on all connections, so can you check please with a voltmeter ? Thanks
Has anyone had these issues but they are not constant? I saw this thread and thought for sure this was the issue so I replaced pre-fuse box (used with 65k miles). I'm still having the same issues this post describes but it comes and goes completely random. Explanation; The high-beam and brake light indicator lights come on dash, the SRS light on center console shuts off, all electronics in car shut off( radio, AC, windows, etc..), wont shift in gear, and engine fan kicks into high speed. Any advice will be greatly appreciated. Thank you
Last edited by mcspecialist; 06-30-2019 at 03:04 PM.
Reason: To note used replacement part
So, happy to tell you that everything is ok right now, I have order just the cut-off relay (the code is a little up) and waiting to arrive. What have I done is to unscrew the 30g circuit cable (4) - fuse f156 - and connected directly to the positive conector at battery. Everything worked like magic!
Attention! This is just a temporary solution, until you get the relay. Of course that you can change the whole F32 prefuse box, but it is more expensive then just the relay (80 eur at dealer) .
I am not responsible for any outcome, for me worked perfectly.
So, happy to tell you that everything is ok right now, I have order just the cut-off relay (the code is a little up) and waiting to arrive. What have I done is to unscrew the 30g circuit cable (4) - fuse f156 - and connected directly to the positive conector at battery. Everything worked like magic!
Attention! This is just a temporary solution, until you get the relay. Of course that you can change the whole F32 prefuse box, but it is more expensive then just the relay (80 eur at dealer) .
I am not responsible for any outcome, for me worked perfectly.
Can you please describe which wire you connected to positive lead? I've replaced the prefuse box and still have the same issue and would just like to bypass the relay all together like you did.
I've replaced the prefuse box and still have the same issue and would just like to bypass the relay all together like you did.
No no, don't do that yet.
A relay is a simple switch, operated by electric coil energizing a contact to close or open.
You wrote : I've been dealing with this issue for over a year now!! It seems to come and go as it wants. I have torn my car up from testing all fuse boxes, digging through both SAMS, replacing the battery, the alternator, and all the while getting a voltage spike in the alternators harness from diagnostics. +++++++ I just ordered my prefuse box for my 08 W204 and CANT WAIT TO CHANGE IT OUT. I really hope this is the final piece for it has been too long and too much at times dealing with this. These issues seem exactly whats wrong, even with the fan going into turbo mode, this usually happens while the car is running and flickers on and off before just staying off leaving me trapped in a VERY HOT vehicle.
To note : It seems to come and go as it wants. <<< this means intermittent problem
Now, with new F32 prefuse box, you still have your old problem....correct ?
Did you buy brand new or a used one ?
Assumed you bought a used one and its relay contact points has worn out to a point where under high amperage loading....it then starts to produce problem...which is low voltage.
Load test the F32 then. Take an accurate 2 digits after decimal, example 12.99 volts digital voltmeter.
Run your engine to operating temperature with all aircond load at maximum and lights too. As per DKBKL photo and red numbers, measure #3 and #2 voltage to ground and also the current coming out of #2.
#3 has a 350 amps fuse, that means it is most likely the input for the prefuse box, for my E400 this is most likely from the alternator.
A battery positive wire also goes into this F32 on my E400 but it goes into F32 from the bottom, not top part.
#2 has 150 amps and 100 amps fuse after a relay, that means this is most likely an output.
Note down the voltage from ground ( negative ) to #3 and #2 and the amperage of the wire coming out of the #2 output. I think you will need a DC clamp meter of at least 100 amps.
Sometimes a relay bad contact show its dark side after certain temperature. So do the test at 1 minute, 15th and 30th minutes.
I have to remind you again what you wrote : It seems to come and go as it wants. This kind of intermittent trouble need patience to troubleshoot, no rush.
A relay is the same as a contactor in a AC 110-480V system.
Its failure mode is usually as follows :
AA. Bad and worn out contacts. Hence must apply huge load to test it and not simple float voltage with no load.
BB. Heat related issue at contact point, after heavy amperage load for sometime then it acts up. So time is your friend.
CC. Coil problem. The coil that pushes down the contact may be not so healthy and its pressure reduced when the coil get hot. You basically get bad contact not due to the contact itself,
but the coil is not giving enough magnetism to close the contact.
Now, my car shows 4 wires into that relay you speak of. I hope unless you know 100% which two wires feed the coil +/- and what are the functions of the other 2 wires, do not try to energize this relay on
your own using direct wires from a 12V source. Just test the F32 as installed.
Remember, my car and your car may not have the same F32. See my part number is A212 540 70 50 and I have ECO-Start-Stop.
The all above mentioned test is to verify that your used F32 is good or not so good at high amperage load. If it is bad, you will have issue at all times with anything downstream of #2 wire terminal.
The only other possible problem point for this F32 is if and when the 4 wires into that relay has bad contact at its connector or somewhere up stream.
Take a look at that 4 wires connector for the relay, use a camera capable of close up, and see if the connector pins are all good and of equal depth on your PC if you need zooming.
NOTE : I assume that when you got a new/used F32, you have inspected that all its fuses are okey and none of their fuse bolts are loose...yes ? Loose bolts means bad connection too and maybe intermittent.
This is where I am upset, because I do not know what are the 2 extra wires into the relay are for ? I know 2 are for energizing the coil....the other 2 for what ?
If the 2 extra wires are actually for sending information to some control unit on the status of this relay as closed contact or open contact ( let's assume this relay is a normally open type ), these two wires alone could be
the culprit too.
Lets do a simple scenario that this two wires are actually connected to another set of mini contact inside the relay, to confirm main contact close or open.
AC 110-480V Contactors do have these extra connection for auxillary switching or as information that switching took place.
Since the 2 extra wires is for information only, there is such a small load on its mini contact points, most likely it will never get worn out......usually so, but who knows ?
I attached a schematic which I forgot where I got it from. I titled it 1-DownloadPDF. pdf it has F32 information and what looks like the relay we speak of.
My apology, I am not familiar and not enough experience with MB schematic, I get confused when looking at their legend and the amount of variation of different models using different F32....:
ASSUME, the above relay is the relay we speak of. I would guess pin 3 and 4 is the power to energize the coil because its written as RSS on & RSS GND on and pin 1 and 2 are the information cables.
Now imagine the pin 1 and 2 wires is having poor contact somewhere within the relay itself or where its original upstream wiring source is.
If due to poor contact this 2 wires give wrong information/status once in a while to some control unit, it can also cause the intermittent problem you are having, even though main relay contact is good
and allow high amperage current to pass thru.
Our cars is so electronically interconnected between the SAM and whatnot and with lots of diagnostic capability, any misinformation from a device supposedly to send a confirmation signal,
may trigger the failure or codes you are getting. Once we handle CAN bus stuff, its unlike simple analog cars of the late 80s where all are so electro-mechanical and much easier to troubleshoot.
Now we are dealing with data signal and electro-mechanical for power delivery.
I dont know how well versed you are with CAN bus, but I am not familiar with it.
NEXT. Assume your test proved F32 and the 4 wires into the relay is all good.
What I would suggest for your next troubleshooting is making sure all the SAM did get good ground/negative.Don't always chase the positive cables only.
If you live in Miami and near the sea, your air is more corrosive than inland cities and it may be more humid too.... all the enemies of electrical system.
I used to fix my friends's yachts electrical wiring in the 90s and damn, a boat is a good DC electric training ground.
Every damn cable and its terminals and MCB/breakers aged so fast thru oxidation and corrosion, a 5 years old wiring on a boat flybdbridge is like 20 years old wiring in car not close to sea.
Concentrate your troubleshooting to find voltage drop while under load, because your problem is intermittent, so it is not a simple as totally disconnected connection or a blown fuse
or 100% worn out relay contact points.
One other detail you may need to check.
The bigger cable get crimped on its end with cable terminal/lug. https://www.pjfallon.ie/image/cache/...-1000x1000.jpg
Do not be surprised some crimping may not be as tight as we expect when inspecting visually or some corrosion has damaged the outer cable strands where the crimping took place and
cable then become quite loose but not very loose. This kind of crimping imperfection/damage under low amperage load won't show. Give a good pull on those crimped cables. 3kg of pull force 3 times would suffice.
Also use your ohms meter feature to detect any high amperage connection which exceed 0.5 ohms resistance is a suspect. Make sure you factor in also your meter leads own resistance when doing this test.
If you can borrow a thermal gun from a friend, like FLIR , 100 x 80 pixel one is not bad already. This may assist you a great deal on finding bad connection which eventually produce extra heat and resistance.
Good luck...
.
Last edited by S-Prihadi; 07-08-2019 at 02:32 AM.
Reason: add info & correction
Thanks for the reply S-prihadi! Lot of info! I also think it's the F32, second hand ones can make a lot of surprises.
Mcspecialist Order the relay itself (A0035421819) and change it yourself. Not a hard job. Then check every fuse inside. When the F32 box is connected, check the voltage on every exit point (at the connector), you should get around 12V. Read again what have I wrote in my previous post. Good luck!
07-23-2016, 05:49 PM
you make me smile again!
