Indyvidual

Having some problems with the sl at the moment.

I havent driven it in a couple of weeks. The fob no longer opens the car. I used the key and gained access. The key will slot into the ignition but will not turn. I thought it could be the front battery but attached jump leads and nothing happened. I thought it might be the rear battery. However I cant access the boot. The key wont turn and open the boot. Erm...help? Any ideas?

Cheers

bobterry99

You really ought to be able to get into the boot, since it is purely mechanical using the key in the lock.

If the key won't turn in the ignition switch, then possibly the switch is not powered. Check for a blown fuse in blocks F32 and F33. Details are in the PDF file attached to this post.

Indyvidual

Thanks. Should I be able to jump start the car from the front battery even if the rear battery is flat?

Rudeney

No, you cannot jump from the front battery. So the metal key does not turn at all in the trunk lock? Or it does not open when turned? Note that once the key is turned, you still have to pull the handle to release the latch.

bobterry99

Yes. Once the ignition key is turned you have c. 30 seconds to engage the starter. If that time period has elapsed, then you must turn the key back to position zero and try again.

Indyvidual

The key turns in the boot lock. It turns 90 degrees anticlockwise and about 45 clockwise. I havent really applied much pressure. Ill add a bit of pressure and try to get the lock to 90 degrees clockwise and pull the handle to see if it will open.

I can't jump the car from the front battery under the hood? I need to jump from the rear battery in the boot/trunk?

Indyvidual

Confused now as @Rudeney said I cant jump start the car from the front battery and you say I can. The manual says I can, but doesnt specify if thats possible if the rear battery is flat. Maybe I need to get into the boot and charge the rear battery first with a booster box and then when thats up and running I jump the car from the front battery with another car?

bobterry99

Since the state of the rear battery charge is immaterial, the manual does not mention it as a factor.

No. Refer to page 31 of the PDF file mentioned in my first post and note that the K57 relay connects the front and rear batteries together in parallel in the case where the rear battery is flat.

K57 will remain energized for about 5 minutes after the engine starts. If it were me I might wait for the relay to de-energize before removing the jumper cables after a successful start.

Indyvidual

OK so basically, attached the jumper cables as normal, switching off all electronic switches including the auto on the headlights. Hopefully get a jump and wait at least 5 mins before removing the cables. This should send enough charge to the rear battery to let the boot open with the buttons again (hoping there are no fuses blown in blocks F32 and F33)?

Will attempt this in the evening and report back!

bobterry99

I presume the SL500's engine will be running; if so, then yes -- there should be adequate power to open the trunk. But if a fuse is blown the engine may not start.

Rudeney

My understanding is that if the rear consumer battery is dead that you cannot "jump" from the front starter battery to fix that - you have to jump or charge the rear consumer battery. Now, if you turn the key and the engine won't crank, or is too slow to turn over, then you could jump start the front battery to fix that problem. Having said that, there were some changes to the BCM that allow the front starter battert to "supplement" a low rear consumer battery, and vice-versa, but I think that was on the SL550, not the S500.

bobterry99

Not true. The vehicle can unconditionally be jumped from the front battery, but jumping from the rear can be problematic. For example, if the front battery is weak and the rear is not, then the power from the donor vehicle's alternator won't reach the SL's front battery or starter motor, and the effort is pointless.

Further, jumping from the rear needlessly exposes the vehicle electronics to voltage spikes that can cause damage. On my car a plastic cover which attaches above the positive post of the rear battery cautions to ONLY jump-start from the front battery.

There were no such changes. From the beginning of R230 production the K57 relay connects the two batteries in parallel in the event of the rear battery being below about 10.8 volts (weak). If the front battery is weak, then the vehicle can not be started unless a little trick is employed: disconnect the rear battery, turn the ignition key to position 2, and within 30 seconds reconnect the rear battery and start the engine.

Indyvidual

Ive run into another problem (these are really adding up!!)
I cant seem to open the hatches behind the seats. Either of them. I need to get access to the fuse box there and cant open them. They seemed to be fine before this problem. The same is true of the glovebox as well.

Any suggestions?

moretech

When you locked the car it locks all the stuff you mentioned plus the consol. Really need to get the PSE pump some power(rear batt.) to undo the lock ups. Need to get the trunk open somehow. I cannot imagine why the key will not open the darn trunk.

moretech

Indyvidual

Once I make it into the boot, should I use a particular charger? (i cant jump the front until I get access to the cubby holds behind the seats, which needs the rear battery to be working). Im hoping to get the boot open and charge the battery giving me access to the unlocking function via the key which I can then use to change any fises and then hopefully jump the car (from the front battery)

Something like this be ok to charge the rear?

http://www.halfords.com/workshop-too...attery-charger

Or this?

http://www.halfords.com/workshop-too...les-up-to-2-0l


Im after the quickest charging option if there is a choice as I have it booked it to see a MB specialist in about 24 hours and will only be able to start charging in around 10 hours.

Thanks guys.

moretech

I would remove the rear batt and have it charged by a local shop and checked for proper operation. Then reinstall it and see where things are. If AGM type batt I notice the charger in the ad cannot do an AGM battery. I do not believe a rear battery should ever be jumped. Even easier just buy and install a fresh rear AGM battery. Really hard to check electrical headaches without knowing what the battery condition is. You could while the rear batt is out do the same to the front battery and see if it will hold a charge. Remember front batt goes in before the rear battery when both are out. Keep us posted how it all comes out.

moretech

bobterry99

You can access the rear fuse box without opening the storage compartment. Simply remove the cover -- the bottom piece in the attached photo. It unclips at the upper edge, I think, though it may unclip from the bottom.

Rudeney

I think you and I are saying the same thing here, but maybe I used the wrong terminology. To me "jumping" means to connect an external power source in order to supply power to the starter. If the front battery is too weak to power the starter, you absolutely do want to connect an external power source to that front battery in order to "jump start" the car. When the front battery is weak, You would not want to put that external power source on the rear battery. If the rear battery is weak, applying external power to the front battery won;t help that. But putting an external power supply on the rear battery would.

Using an external power source to charge the rear battery is fine (assuming it is properly connected), but "boosting: or "jumping: it in hopes of supplementing a weak front battery is (a) futile and (b) risky.

Take a look at these two WIS docs and let me know how you interpret them:

Through MY2008: http://benzbits.com/R230/BatterySystem.pdf
MY2009+: http://benzbits.com/R230/BatterySystem2009.pdf

I think that as of MY2009, the system was altered so that both front and rear batteries can "help" each other, but prior to MY2009, the only option was that a weak consumer battery could be supplemented by the starter battery, but not vice-versa. I could be wrong here, but that's how I have always interpreted the difference. .

bobterry99

That is false. If the rear battery is weak, then the K57 relay energizes and connects both batteries electrically in parallel.

Nothing I read suggests this is the case. Operation of the K57 relay is solely dependent upon the "on-board power supply voltage" and never the starter battery voltage. Note that in this document the rear battery is referred to as the "on-board electrical system battery".

Rudeney

This is what I was reading:

So what you are saying is that the "undervoltage" only applies to the consumer battery, and not the starter battery? I assumed since there was no distinction made in that paragrach that it applied to both.

As for charging the consumer by connecting to the starter battery, I don't see that working unless the BCM has switch on relay K57 to put the two batteries in parallel. It does that in an undervoltage situation, but I am not sure what that is. The WIS doc mentions that after the BCM cuts-in the starter battery, it won't cut it out until voltage reaches 12.5v for 3-7 minutes (depending on the severity of the undervoltage situation). I do see it mentioned that Stage 1 low voltage is M< 10.6v. Maybe that's the threshold? If so, that means if the consumer battery voltage drops below 10.6v, and the K57 relay is activated to put the batteries in parallel, the you could charge the consumer battery via connection to the starter battery.

Aussiesuede

Bobterry99 & Rudeney, I was told that there is a risk of damage to the BCM if jumpstarting and was advised to never jump start, but rather remove the starting battery and charge it independently. Was that incorrect advice??? Once the car is started, then the BCM will allow for charging the consumer battery, presumably giving access to the trunk. I defer to both your superior knowledge of the system, so your advice would be most appreciated. Thankfully I've not yet run into a situation of having a dead starting battery, but should I, I'd like to know if there really is any risk to the BCM through jumpstarting the front battery. As finicky as the R230 is to voltage fluctuations, I'd tend to err on the cautious side. Heck, when I'd previously thought about this potential I'd decided that even if this were to occur in the field, I'd preference removing the front battery and installing it in the donor/ jumpstarting vehicle and letting it's charging system apply a charge then before reinstallation, but realise that I'm a bit of a hypercondriac when it comes to exposing the R230 to unusual voltage spikes. I'm really interested in your input(s).

Aussiesuede

If there is no power to the PSE pump, it won't open. That keyed lock isn't the normal Tumbler/Latch release as you normally imagine it. All the keyed lock does is manually move a plastic lever that forces it into the latch actuation mechanism. But if there is no power to that mechanism, then it can't release. I know MB does this for ultimate security purposes, but it is frustrating when trying access the vehicle via key. Here is a tutorial I did in the CLK section regarding operation of the MB locking system. Have a view at post #5 and you'll understand just why keyed entry without power will be unsuccessful..

https://mbworld.org/forums/clk-class...rill-lock.html

Rudeney

Obviously, if you remove the battery from the vehicle for charging, then you eliminate any worries about damaging the BCM electronics. According to WIS< the proper steps for battery disconnection is disconnect the consumer battery first, then the starter battery. And to reconnect the starter battery first, then the consumer battery. In other words, only work with connecting and dicconnectiing the starter battery once the consumer battery is disconnected.

Having said that, it is fine to charge the consumer battery without disconnecting anything. In fact, many people keep connect a C-Tek charger on theirs so the consumer battery does not drain after several days (or weeks or months) of being garaged.

Regarding the hard key mechanism on the trunk lock, yes, it does just move a plastic lever into the mechanism, but that plastic level allows the handle to then unlatch the lock. In other words, you insert the hard key in the lock, rotate it counter-clockwise, and while holding it there, squeeze the handle. The latch should then open - no electricity or pneumatic pressure needed.

bobterry99

Yes. The document states, "the battery cutoff relay is controlled depending on the state of the on-board electrical system." The on-board electrical system is powered by the consumer battery and comprises the entire electrical system except for the starter battery and starter motor armature.

The BCM directly controls K57. The voltage threshold for energizing K57 and cutting-in the starter battery is 10.8 volts. See the attachment which quotes the relevant section of the WIS document.

Mercedes designed your car's electrical system to withstand the rigors of jump-starting. Surely if they thought the practice practice posed an unacceptable risk they would not have the procedure detailed in the owner's manual. Still, you do read of stories where electronics have been damaged and you have to wonder. If there is a risk I doubt anyone can quantify it.

I have jumped an R230 once and other modern Mercedes perhaps a dozen times with no ill consequences. It's my belief if proper procedure is followed there is very little risk.

Rudeney

Bob, one thing I am unclear about is this: Does K57 cut in if the car is just sitting there and voltage drops below 10.8, or would it only cut in with the ignition on? That would be important for the OP to know when trying to "boost" the consumer batter in order to open the trunk.

Also, I agree 100% with you on the car being designed for the possibility of jump starting. I hear so many people claiming that jumping will blow electronics and that's just plain wrong. Proper jump starting or charging won't damage anything. I've probably jump-started at least 100 MBZ cars and not damaged a single one. One thing that does happen is that a dead battery can act like a giant resistor so that jump starting won't provide enough amperage to the starter. In that case, disconnecting the dead battery works like a charm (I had to do that many times for cars sitting in the storage lot).