R129 SL Soft Top Problem Overview

R129 SL Soft Top Problem Overview

Posted by Carl Burgess on 1st Aug 2018

Are you having R129 soft top problems? It may be stuck, or it won't close, won't reset, needs manually opening, or you think your controller needs fixing?

Soft Top Mayhem!

Problems with raising and lowering soft top roofs can be frustrating and feel illogical at times. It is one of our most requested diagnoses for the R129.

The hydraulic and electrical system to achieve this is beautifully engineered (in my view) and, as such, any issues can be addressed using a methodical approach.

A set of micro switches, locks and hydraulic valves must all function well in turn to allow the next process of motion.

It's not always immediately obvious whether the roof control unit is at fault, or one of the above components.

The first step

Look at fault codes if present. Early models will need a flash code reader. On later models, STAR diagnosis may be required.

Next steps

It's fairly simple to test the switch function with a meter, by manually opening and closing the locks individually.

However, hydraulic locks may not diagnose as faulty, even when the micro switches are not switching over correctly.

Window position switches can fail in early cars and the hall sensor within the window motors on later variants.

It's a step by step approach to work through the systems' sequence of events.

Things to note

- Often raising the roof and lowering manually a few times can get it operating again, especially after a dormant winter.

- Low battery voltage will impair performance and a flat battery can store fault codes that may need clearing.

If these tests are clear..

If all tests of the above are clear, then indeed the roof control unit may well need replacing (search our store to see if we have one in stock).

Either way, a health check on your soft tops' components can be time well spent.

If you need any further assistance, please ask the gurus or email guru@r129.co. We're here to help.

Thanks, Carl at R129 Co.