Electrics: Braided strap torn, unattached from Center next to tensiione

[Mmaxxxx]

I have a ‘05 XC90 V8 awd. Batteries die within 2 or 3 miles. Can’t figure out why. By the alternator, there’s a green wire unattached and a grey wire unattached. Sticking partly out of the engine, torn and unattached, is a braided strap… looks like a ground, from in between the pulleys and I can’t figure out where it goes or where the rest of it is. Please help. I just bought this car not long ago and was told alternator is new and I know the person that had it last stored it for 6 months before selling it but she wasn’t very mechanically savvy.

[Wagon Sailor]

It is almost certainly a ground, as you say. Can you at least find where one end is attached?

[Moose Test]

The correct replacement alternators for the V8 are scarce and expensive, which always leads to the possibility that the incorrect one has been fitted.

Also, the job itself is painful, which again leads to the possibility that it wasn't done correctly or with requisite care and attention.

Unless you've reasonable spanner skills and lots of time and patience, I suggest taking it to a garage.

The braided strap is very likely to be the engine ground, attached to the passenger side (on a US model) inner wheel arch and the rear of the block.

The green and grey wires, based on their colour, *could* be the LIN bus (digital communications to the CEM) connector (or what's left of it), which should be plugged into the correct alternator. IF it is, it is likely to cause problems (I'd be surprised in any case if you weren't getting the "Power System Service Urgent" message on the dashboard) and it is likely so because a) it wasn't reconnected at all and has become detached, b) it was but fell off anyway or c) the incorrect alternator has been used and thus there was nothing to attach it to.

[Mmaxxxx]

Thank you so much. I was thinking LIN wire. Yes I get the red power system failure after about 3 miles down the road with a fully charged battery… total loss of power couple minutes later. It’s weird that the braided cable comes out of the middle of the engine though. Because I already have an engine ground close by that, running to that fender there. It’s the inverted block so yeah it’s facing the right side and this cable … looking all chewn-up comes right out from in between just next to the tensioner pulley…. Anyways your post has been a help regardless. Thank you so much for even replying. I like this car so much and it has massive potential but I’m just a union carpenter so I can’t afford to get jerked around by some of the mechanics here. I usually try to learn all I can and do it myself. Usually I do very well up until now. I’m stumped.

[Moose Test]

On the ground strap, if it's the one I'm thinking of, I've attached a photo of it with the serpentine belt removed. It's very difficult to see to where it attaches on the engine, as the general area of the mounting point is partially obscured by the plastic engine covers. I suspect that you'll need to remove these in order to gain any access, which in the case of the rearward cover, will also require you to remove the upper engine torque rod (the metal bar that runs horizontally across the engine bay and which attaches to the suspension towers). A pain but not that difficult.

Vida's parts diagram for the strap shows it attaching to the rear face of the engine block, about 3/4 of the way down, in close proximity to the serpentine belt.

It really does need to be connected but won't be the only/main issue, if the LIN wiring is disconnected.

You will need to check that the LIN connector and wiring are in place and intact - there's no chance of proper operation without it, as the ECM and CEM use this to control the voltage output and charging. No-go without it.

If the connector has been broken or detached (and presumably lost) from the cable, there's a chance that a Volvo dealership can supply a replacement part. At least here in the UK, they seem to be able to supply a myriad of connector and connector repair kits for the looms. However I suspect that it won't be an easy task due to the shear difficulty of access.

Good luck.

[Mmaxxxx]

I’m attaching photos. The red thin wire is connected to the threaded cable part(what’s left of it) to show it clearly in the photo. The other is the top of my alternator… grey and purple wire connected to green, but the other wire is just hanging like it was chewn off.

[Mmaxxxx]

Does the other wire at the plug atop the alternator have to be a ground? Whoever worked on this before I picked it up was AMAZING!

[Moose Test]

Originally Posted by Mmaxxxx

Whoever worked on this before I picked it up was AMAZING!

That's one description. I'd go with "utterly clueless" or "f**kwit" depending on how generous I was feeling at the time.

Looking at the state of what struck them to be an acceptable repair, I wouldn't trust anything about the installation of that replacement alternator without checking it/having it checked, starting with it actually being the correct unit. I *suspect* that it isn't. I did try to examine the alternator setup on my own V8 for you today for reference but without removing the engine covers or going underneath, I just don't have a good enough line of sight on the area of interest.

What I think (and I stress, it's a theory) is that this isn't the correct alternator for the vehicle. Which meant that the original Volvo connector on the loom didn't match that on the replacement alternator and so our "mechanic" cut it off and then made that bugger's muddle with the connector from the donor vehicle and the remains of the severed LIN wire.

What leads me to this is that the wiring diagram shows only one LIN wire to the alternator's voltage regular, a green wire. Which you have but which has been cut. LIN ground is through the alternator's body, to chassis ground. I think the correct Volvo voltage regular has a connector with only a single terminal, taking that one green wire. So the remaining connection that you see flapping about on yours shouldn't be there at all, and hence isn't connected.

Even if I'm wrong, that twisted splice is no-go and needs a proper repair. Can you imagine what vibration is doing to the signal integrity on that digital comms bus?

The braided ground that you also shown in your pictures IS the engine ground and that needs to be repaired too. It's likely that without it, there's a higher resistance ground path than is really required for the alternator and the other engine-based electrics. It seems that these can still be purchased new from a dealership but if you can find one, a car breaker will be cheaper.

[Mmaxxxx]

Thank you so much. I’m going to get that car up on a lift, take the alternator out and replace the braided strap also. I appreciate your help immensely! Again, thank you