Hi all. When taking apart the front suspension I noticed remnants of what looks like a grounding wire attached to the screw that holds in the wheel speed sensor. So I assume this grounded the wheel assembly to the car chassis. But I have not been able to find where the other end connected exactly. Up under the hood someplace. Is/was there a specific place where it connected to?

Thanks!

Bobby

 

G'day Bobby

My car has a complete strap on the RHS and only the remnant end fittings on the LHS. The complete strap bolts to the sensor mount and the other end is attached to a join in the hydraulic brake line in the wheel well. A secure earth for the ABS I'd guess.

I haven't noticed anything unusual on the side without the strap.

My car also has an earth strap between the bonnet/hood and the top radiator mounting rail and I have no idea what purpose that serves.

Cheers,
Jeff.

 

The one that attaches to a steering rack nut? I lost mine a while ago haven’t got around to fixing it.

 

That makes sense. There were shreads of the original insulator running up as far as the brake line connection at the wheel well. But nothing beyond that. So it seems that's where it terminated. Though it sounds like it's not truly needed, I've ordered some 1/4" braided wire, terminals and covering to replace it anyway. Something to do while I wait for other parts.

Thanks,

Bobby

 

Hi Bobby,

Those ground straps are to protect the wheel bearings from damage due to static electricity and other stray currents. See pdf page 21 of the attached document.

The ground strap to the hood is to help protect the sensitive engine management systems from electro-magnetic interference/radio frequency interference (EMI/RFI) by using the hood and body as a Faraday Shield to shunt those signals to ground.

The ABS wheel speed sensors are grounded via their two-wire harnesses that connect directly to the ABS/Traction Control Module.

As far as I can recall, these wheel hub grounds are not documented in the literature, but they can connect to any good ground point on the body. I think a sheet metal screw was typically used to attach the ground to the wheel arch or such. Much of the suspension is electrically isolated from ground by the rubber bushings and grease-filled ball joints (though the isolation is imperfect), so you don't want to connect them to the steering knuckle, control arms or subframe, for example..

Cheers,

Don

 

Thanks Don!

Bobby

 

Regarding Don's post about grounding, in which he says that ground wires should not be attached to the steering knuckle, control arms or subframe, should I ask my service provider to disconnect the ground wire that they said they had "REPAIR LEFT FRONT GROUND WIRE TO STEERING KNUCKLE". When I asked them what may have not been working when that ground wire was not connected to anything they said they didn't know and that Jaguar said the wire should be connected to the steering knuckle. Subsequent to that service I have been puzzled by the charge level dropping from 100% to 65% overnight after fully charging the battery. Is that something to do with what they did with the ground wire.

Thanks in advance.

 

Hi Sheltoncar,

That's a good question. To clarify my earlier comment, you don't want the final termination of the ground strap to be on the steering knuckle, because the electrical path for ground would have to pass through the ball joints, which of course are filled with grease, so they do not offer a reliable path for electrical current. The final termination of the ground straps should be to the body, which constitutes the main ground bus for the entire vehicle. But it is fine to secure loose sections of the ground strap to the steering knuckle and control arms with zip ties as long as the final termination point is to the body. I hope that is more clear.

Cheers,

Don

 

Thanks Don. I will ask them if they made it the endpoint or just zip tied it.
Robert

 

Hi Don,
They attached it to a nut that in the photo they showed me appears to be close to what I believe is the steering knuckle.
When I raised your comments with them they said that they did it that way because that's how it is on the right front side.
If it is not to be connected there, where should it be connected?
I assume that, unless they cut off some wire, the length would dictate to quite a degree just where it could be connected.
Thanks,
Robert

 

Hi Robert,

I don't have an X300 here at the moment to inspect, but the ground strap should not be terminated at the steering knuckle/vertical link or control arms because they are all electrically isolated from the body of the vehicle by ball joints filled with non-conductive grease and rubber bushings. Here's the diagram showing the steering knuckle/vertical link, Part #1:




Here is the steering knuckle in context with the control arms/wishbones:



You can see that the knuckle is isolated from the control arms by the ball joints, and the control arms are isolated from the front suspension subframe/crossmember by rubber bushings. Furthermore, the subframe is isolated from the vehicle body by rubber Vee mounts. So the hub/wheel bearing ground straps need to terminate on the actual monocoque body of the vehicle. My recollection is that the original termination point was somewhere on the inner fender or wheel arch.

Cheers,

Don

 

Hi Don,
Many thanks for the diagrams. I would say they attached it to Part # 23. So the question is what is the other end attached to - the hub/wheel bearing or the vehicle body. I will ask them.

Cheers,
Robert

 

G'day Gents,

I had a look under my car just now and it looks like the upper end of the earth strap is fitted to the brake line bracket around the actual metal part of the brake line which would be a nuisance if you needed to replace the earth strap as you would have to disconnect the brake line etc etc.

The lower end of the earth strap is secured by the little bolt which holds the ABS wheel speed sensor in place.

See the attached pix.

HTH cheers,
Jeff.



Brake line, ABS lead and earth strap.




Lower end of earth strap secured behind ABS speed sensor bolt.

 

Hello Jeff and Don B.,
Thanks Jeff for your posting The setup you describe differs from Don B's earlier post that one end should be connected to the vehicle body and the other to the wheel/hub bearing and that he couldn't find info in the literature. On my car one was connected to the steering knuckle on the RHS and the one on the LHS was not connected, so they connected it to the steering knuckle. I assume the final termination is at the vehicle body, as Don B. suggests, but I would am hoping for a definitive post about the part being grounded. Is your connection to the ABS speed sensor bolt in essence a connection to the "wheel/hub bearing"?

Cheers,
Robert

 

Hi Robert,

Jeff's photos are very instructive. Yes, to answer your question, the end of the ground strap connected by the ABS wheel speed sensor screw forms an electrical connection to the wheel bearing housing. The other end of the ground strap is connected to the brake hose/line bracket, which is connected to the body, so this completes the electrical circuit to shunt any static charge to body ground.

Thank you, Jeff!

Cheers,

Don

 

Thank you, Jeff!

Cheers,

Don

Hello Don and Jeff,

Thanks Don for confirming Jeff's info as correct. And thanks to Jeff for posting it. I can now ask my service provider to make the correct connections. I am 85 and not physically able to work on the car.

Cheers,
Robert