Electrohydraulic Motor Mounts: Function Test?

Hello everyone,

I noticed that the cable connection to one of the electrohydraulic engine mounts on my A6 had corroded. I then repaired it by soldering and insulating the connection.
The only thing I know about how it works is that the bearings are set to 'soft' when the engine is idling and to 'hard' under load. I quickly found that pin 50 of the engine control unit (speed signal) is connected to the control unit for these engine mounts.
Is there a way to tell if everything is okay without having to take measurements? Has anyone ever tried to determine how it 'feels' when the cables are disconnected or when the bearings are no longer working?

Hello!

Pull out relay 6, located in the footwell on the passenger side, take it for a spin, and then you'll notice the difference!

You can also manually connect them >> Disconnect the relay >> Connect 12V directly to the contacts of the two bearings by bridging them >> The motor mounts will become stiff.

Best regards,

Andi.

Hello!

Pull out relay 6 in the footwell on the passenger side, take a drive, and then you'll notice the difference!

Hello Andi,

Okay, so 'fail-safe' is 'hard.' I'll try that out, thanks.

Dirk.

Can someone explain how these types of warehouses work?

Best regards,

I may not know the exact structure of these warehouses, but here's how they might work:

The electrohydraulic damper will have a chamber with a piston in the center. The piston divides this chamber into 'two' chambers, which are connected by a channel, allowing the damping fluid to flow from volume A to volume B (otherwise, the piston wouldn't be able to move). By actuating an electromagnetic valve, the 'size' of this channel can be controlled, and thus also the damping effect (a small hole results in high damping, which is used to absorb strong vibrations, while a large hole has the opposite effect).

I hope you understand what I mean (it would be easier to explain with pictures, but I don't have any web space...).

Best regards,
Andi.

Hello fellow enthusiasts,

The hydraulic bearing has a large upper chamber and a lower chamber, which are connected by a nozzle channel. An outer rubber membrane connects the upper bearing to an air channel that vents to the atmosphere. Small, high-frequency vibrations are dampened by the rubber membrane (up to 1100 RPM). The rubber membrane deforms and displaces air from the air channel. Small vibrations cannot force the hydraulic oil through the nozzle channel.
When the tank is full, a solenoid valve closes the air channel, and an air cushion forms beneath the rubber membrane. This creates resistance, preventing the membrane from vibrating. The vibrations are then forced through the nozzle channel into the lower chamber. The lower chamber also has a rubber bellows, which deforms when oil flows through the nozzle channel.

Best, Manuel.