Rough engine running and noises when starting or switching off the engine are in some cases too quickly associated with a possible dual-mass flywheel (DMF) defect. Often though the cause of these faults can be found in an unexpected place – in the vehicle electrical system. In this workshop tip we look at this issue and show you that, for instance, dirty ground stubs may be the cause of a fault with the vehicle electrical system.
If, for instance, you have a fault with the ignition system, this becomes apparent with noises such as rattling or chattering from the area of the dual-mass flywheel (DMF), the clutch or the transmission. The engine may also take longer to start as a result or the engine may run rough. As part of troubleshooting, the electric contacts should be checked and cleaned where necessary. These contact surfaces are, however, often difficult to access, which makes cleaning more difficult.
If the contact surfaces are soiled with oxidation or corrosion, the contact resistance of the contacts is increased. This leads to a drop in voltage, which may cause faults with electronic components or cause the vehicle electrical system to fail.
Our useful tips provide only an overview. The installation instructions and operating instructions provided by the vehicle manufacturer and the warning and safety instructions contained therein must be observed! All work must be performed by a trained professional. The pictures used and the procedure described in our tips are examples and may vary depending on the vehicle manufacturer and axle design.
As a solution, ZF Aftermarket offers the SACHS cleaning system for electric contact surfaces. This allows you to clean easily and professionally even inaccessible corroded or oxidized contact surfaces and eliminate contact problems.
The package includes a through-ratchet with rotary handle, two flexible extensions that allow you to clean even hard-to-reach areas, as well as a 1/4” adapter, self-adhesive hook-and-loop pad, web rings and battery contact cleaner with protective cap.
Procedure for cleaning the contact surfaces
1) Assemble the cleaning tool.
2) Loosen the battery terminal clamp and remove it from the battery terminal. Observe the vehicle manufacturer specifications.
3) Check the battery terminals for corrosion and soiling.
4) If necessary, clean the battery terminals with the battery contact cleaner.
5) Keep cleaned battery terminals dry and free from grease and do not preserve with lubricants.
6) Check the battery terminal clamps for corrosion and soiling.
7) If necessary, clean the battery terminal clamp with the battery contact cleaner.
8) Keep cleaned battery terminal clamp dry and free from grease and do not preserve with lubricants.
9) Loosen screw connections of the electric contact.
10) Check the electric contact surfaces for corrosion, oxidation and soiling.
11) If necessary, clean electric contact surfaces with the appropriate adapter, hook-and-loop pad and web ring.
Note: Use the gray web ring for lighter soiling and coated surfaces (e.g., cable eyes). Use the red web ring for heavier soiling and uncoated surfaces (e.g., grounding point to the body).
12) Keep cleaned electric contact surfaces dry and free from grease.
13) Tighten the screw connections of the electric contact to the tightening torque specified by the vehicle manufacturer.
14) Connect the battery terminals and tighten them to the specified tightening torque. Observe the vehicle manufacturer specifications.