W126 560SEL airbag steering wheel module - SRS light intermittent - is it the module or the clockspring

Started by Hugo_Darlinghurst, 06-09-2024 11:18 AM. 10 replies. 2,418 views.

06-09-2024 11:18 AM

Hugo_Darlinghurst Senior Member

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Join Date: Feb 2010
Location: Darlinghurst NSW
Posts: 524
Club: Mercedes Classic Drivers Australia (MCDA) - chapter committee
Car: 1968 W108 280SE 5.0 Coupe

need some advise.

1991 560SEL. SRS warning light intermittent over the last 6 weeks. Currently on, was off this morning. Self-diagnostic via the plug shows code 14 (drivers airbag circuit fault, intermittent).

Code 14 on the 560SEL can be either:

The airbag module itself (rare - the modules from 1991 are usually still healthy)

The clockspring (the spiral cable inside the steering wheel hub that maintains continuity through steering rotations) - common at 30+ years old

The harness between the clockspring and the airbag connector (uncommon)

I would like to test the clockspring before committing to disassembly. Is there a continuity test procedure for the 560SEL clockspring with the airbag removed?

06-09-2024 12:18 PM

Vasilios_Billy

Lifetime Benzer

Join Date: Mar 2008
Location: Campbelltown NSW
Posts: 1,699
Club: M.A.L.A.K.A.S.
Car: 2020 AMG GT C

Hugo.

Yes! Clockspring test procedure for the 560SEL (W126 from about VIN 126.039-1H-022000):

Disconnect battery, wait 60 seconds for SRS capacitor to discharge.

Remove the steering wheel airbag module (two T30 Torx from the back of the wheel).

Disconnect the airbag connector from the clockspring output.

With multimeter on continuity, place leads across the two pins of the clockspring output.

Rotate the steering wheel slowly through its full range (lock to lock). Continuity must be maintained throughout.

If continuity is lost at any point, the clockspring has an internal break and must be replaced. Mercedes-Benz part A 126 460 03 04 (varies by production date), about $380 retail at MB Sydney Service in 2019.

Note: the clockspring is sensitive to forced rotation when not installed in the steering column. Do not rotate it more than the original installation range when bench-testing. The spiral cable inside can over-extend and break if you rotate beyond design limits.

07-09-2024 10:48 AM

Hugo_Darlinghurst Senior Member

★ Gold

Join Date: Feb 2010
Location: Darlinghurst NSW
Posts: 524
Club: Mercedes Classic Drivers Australia (MCDA) - chapter committee
Car: 1968 W108 280SE 5.0 Coupe

Vasilios - tested as you described. Continuity lost at about 1.5 turns to the right from centre. Clockspring confirmed faulty. Ordering replacement from MB Sydney service today. $380 and 90 min to fit.

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