2008 Mercedes R230 SL550 battery warning and charging-fuse replacement

djbadeaux separately reported a blown fuse and a cleared warning after replacement. soldbydon later reported another confirmed blown F52f1 and a cleared icon. In contrast, bill morrow reported a dealer reset and connection checks resolving his issue for about ten days, while psrllc found both fuses good and said the warning returned immediately after clearing. These reports support keeping diagnosis separate from the warning symbol; they do not make one fuse the cause in every case. _rodeo_ reported intact removed fuses and a warning that persisted after a new rear battery. Much later, he said he cleared the stored fault with a diagnostic system and had no red warning for over a year, while noting reduced driving during the pandemic. This is a separate reset outcome, not proof that every warning only needs erasure.

A later exchange clarified that measuring each fuse terminal relative to ground differs from measuring directly across the fuse. CPDay cautioned that voltage on both terminals alone did not prove continuity in his interpretation of the dual-battery circuit. Separately, WebbJAC described a relative’s SL350 with the opposite charging imbalance and corroded fuse-terminal contacts, then corrected his own earlier fuse-size terminology from Mega to MIDI. Those are separate observations, not confirmed causes on CPDay’s SL550; this review does not turn the discussion into live-circuit meter instructions.

On a separate 2003 SL500, vegassl replaced the regulator and both footwell fuses without clearing the warning. He later cleaned heavy corrosion from the rear SAM and reported improvements in several electrical functions. Fully charging both batteries briefly removed the red warning, but it returned after driving when he reported inadequate charging. Alternator replacement was still described as in progress. A later message says the car was running well but does not supply a clear final charging diagnosis or long-term SAM result.

SocksSL500’s separate 2003 SL500 had intact removed fuses and later showed low reported charging values with the regulator run-status signal off. After fitting both a regulator and a K57 relay, he reported 14.1–14.3 V at both batteries, the run-status signal on and the warning gone. He suspected the regulator, but two parts changed together, so this account does not isolate one component or explain CPDay’s blown fuse.

CPDay emphasized separately testing the fuses after his experience with the starter battery not receiving charge. bobterry99 emphasized checking actual charging behavior and reading faults from the vehicle power-supply controller when the batteries appeared to charge. The discussion includes different measurement contexts and reported faults. It does not establish that a persisting red icon always means a failed fuse, control module or alternator.

Working on a 2006 R230, CoolBlueGlow first described F52/1 as blown after a jump start, but later corrected the finding: after removal, the fuses were not blown. This is therefore not another confirmed fuse-replacement success. The contributor described removing the passenger under-dash panel and kick-panel carpet to gain room for the subwoofer, and noted a conducting strap above the smaller lower fuse. He emphasized following the vehicle manual for isolating and reconnecting both batteries; no remembered connection sequence or tightening value is supplied here.

CoolBlueGlow interpreted a 2002 document and his 2006-car experience as showing that the red warning would not clear on its own. Tom Manning disputed that narrow account of the warning, reporting handheld-scanner resets and retention of some settings after battery disconnection. On CPDay’s 2008 SL550, fuse replacement alone cleared the warning. CoolBlueGlow later qualified his claim that convenience settings always needed resetting and acknowledged that the reason for the differing cars’ behavior was unknown. Suggested year-specific software differences remain speculation; the icon alone does not establish a failed part or a universal reset requirement.

sbournazos had reported that a new voltage regulator had not restored charging. After removing the alternator, he found melted plastic under its rear cover. He subsequently replaced the alternator, belt tensioner, pulley and belt together and reported that everything was working again. His later post explicitly identifies a 2006 SL500. This outcome belongs to that vehicle; replacing several parts together does not isolate the effect of one component.

MSMBLover reported that both fuses passed continuity and visual checks and that both replacement batteries had been load tested. The red warning nevertheless remained. Replies proposed different explanations, but the contributor did not report a confirmed diagnosis or repair outcome in the reviewed thread.

Fountain35 described a 2004 SL500 showing consumer-electronics and red workshop warnings after sitting for about three weeks. He later said the dealer cleared the code and the car was fine at that point. The dealer suggested the trunk battery but was not certain. Swapping batteries with his E55 was a plan, not a completed test or a confirmed battery diagnosis.

In another vehicle’s account, bill morrow showed his SDconnect equipment and later described connecting it under the dashboard of his SL55. He reported that it communicated wirelessly with the laptop. His photographs show the equipment and diagnostic screens, rather than CPDay’s fuse work. They are not evidence that this warning has one universal fault code or that connecting a scanner by itself repairs the fault.