Soft Top Issues Fixing Guide

Soft Top Issues Fixing Guide

Are you having soft top problems with your Mercedes Benz R129 SL?

It is one of our most requested diagnoses for the R129. Problems with raising and lowering soft top roofs can be frustrating and feel illogical at times. The roof could be stuck, won't close, won't reset, needs manually opening, or you may think your controller needs fixing.

However, the hydraulic and electrical system surrounding the soft top operation 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 Process

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

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

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

4. Window position switches can fail in early cars, as well as the hall sensor within the window motors on later variants.

5. As you begin your step-by-step approach to work through the systems' sequence of events, please also be aware of the following.

- 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 Tests Are Clear..

If all tests of the above are clear, then 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 is time well spent.

If you need any further assistance with your R129, just contact us. We're here to get your R129's summer-healthy!

Thanks, Carl at The R129 Co.

1st Jan 2020 Carl Burgess

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