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Pete, Mercedes Mechanic
Category: Mercedes
Satisfied Customers: 28772
Experience:  Over 15 years experience as a Mercedes dealer technician
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Retractable top on 2009 SL550 won't operate, Rear battery is

Customer Question

Retractable top on 2009 SL550 won't operate, Rear battery is recent. Indicator shows partially opened roof, and instructs to reference owners manual, which I don't have.
JA: Have you tested the battery with a voltmeter? And can you see if it's leaking or not?
Customer: Battery is almost new and has been charged, gauged at 12.2V.
JA: Are you fixing your SL550 yourself? What have you tried so far?
Customer: This happened a few months age and it was the rear battery was bad and would lose voltage in a few hours. That's when I replaced it. Now the same symptoms lead me to re-charge it, but with no change in results.
JA: Anything else you want the mechanic to know before I connect you?
Customer: no
Submitted: 1 year ago.
Category: Mercedes
Expert:  Pete replied 1 year ago.

Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

The biggest issue that causes this fault on these is one of the micro switch/sensors that send signals to the roof control unit on what position the roof components are in.When one fails it sends a false message saying part of the roof is open or didnt close properly which in turn you see this message here.Usually this requires a dealers SDS machine or compatible scan tool to check the fault codes in the roof computer as well as monitor the switches to locate the one at fault needing replaced as there are several of these.

One thing you can check is with your trunk open and your roof in the closed position there should be two flaps on the inside of the trunk lid that should be flush up against the trunk lid.If one is hanging even slightly more then the other Mercedes had released a bulletin to replace the gear housings for these flaps to correct this issue and this can cause this fault as well.

Other then this if these flaps are snug up against the interior of the trunk lid then a scan tool or dealers sds machine is needed to read the switches to locate the one at fault needing replaced.

Diagnosis for this can usually be around an hour and repair will vary depending on which is at fault.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service,your 5 star rating is appreciated.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete