Just Purchased - What is this.

[amblerman]

Another note on this.

As I've said , I'm not an electrician. Before working with any electrical connections, make sure you do enough research and are comfortable working around electricity and circuits. Doing tests like I outline below can be very helpful but you do need a basic level of understanding and comfort to make sure you are doing things safely for both you and your car's sake.

If you search on "voltage drop test" I think you could determine where things are failing
If you have access to a multimeter the test is quite simple. Essentially you are measuring voltage at each connection and seeing where things drop. That could be in indication of a bad connection or source of higher resistance.

For example,
Suppose you get a measurment of 12.8V when measured -post to + post on battery.
Then you measure -post to +battery clamp and found only 12.3. That would indicate a .5 v drop between your + post and + clamp. This would be an indication there was something wrong (ie corrosion, poor connection, etc) between the battery post and the clamp that is causing the voltage to drop.

However, suppose -post to +battery clamp was still 12.8V. That means the connection there is fine.
Then you measure -post to next connection point past +battery clamp (ie end of one of the wires coming out of + clamp)

If that measured 12.3V, then there was a .5V loss somewhere in that connection. for example it could be:
a) poor connection between + batter clamp and wire (corrosion or failing connection)
b) something wrong in wire itself
c) something wrong at the connection point at other end (not the + battery clamp end. )

Once I understood the basics of this test, I have used it to find problems. I actually started with -post to +post to get my test voltage. Then I tested -post to final connection point and did see a voltage drop. Then in was just a matter of finding where it dropped off.
In my case I found a failing connection at my + battery clamp that to be honest, I should have found just through visual inspection but I didn't.

Just doing the voltage drop test confirmed I had a voltage drop somewhere and then forced me to look at each segment of the circuit. Eventually I found the weak link..

[June]

Do you think that might be causing the
battery drain and
the driver seat forward and back control from not working too?
All the other controls seat controls work.

The cable below it is the lead to the battery in the rear of the car. My car too had weak battery issues leading up to the failure. My alternator and starter are still original as installed at the factory with 197K. Looks like the fuse box and cable failed at 134K on my car. What mileage is on your car? I now have 197K so at 60K later all is still fine with the repair. My car has always started instantly, so no long crank time caused the failure. Being as your car is used, you have no way of knowing what has happened throughout its life. It may have a junk rebuilt or Chinese starter in place drawing too much current as has been suggested. I just know your car is the same year as mine and has the identical setup. My car has always had dealer service including batteries. So the faulty fuse box has to be a design flaw rather than incorrect battery or bad starter. My car was built 05/2003.

When the car died completely in the service drive after the new battery was installed. My mechanic went straight to that connection
and took it apart and cleaned and tightened everything down and proceeded to order the fuse box and cable. That's how I know mine looked like your photo and a week later it was burned up and I took the photo. So the connection was tight and clean when I left the service drive that day. I vaguely remember the car had gremlins weeks leading up to it dying that day. I just can't remember exactly what they were. These cars get pissed off when the battery is weak even though all else is normal. June

[PainterPaul]

Hi
Mechanic changed the cable and 1/2 the fuse box. It too had melted.
He complained about the 5 feet of wire snaked all through the engine.

Thanks for your help

[amblerman]

Hi
Mechanic changed the cable and 1/2 the fuse box. It too had melted.
He complained about the 5 feet of wire snaked all through the engine.

Thanks for your help

You're welcome. I (and everyone I'm sure) is glad you caught it before too much damage was done

[PainterPaul]

Next issue

Stop Brake light message.

brake lights don’t work when you step on the pedal.

There’s power to the relay. He’s checked all the fuses and changes the bulbs.

Mechanics gotten frustrated and seeing if bleeding the brakes helps.

Bleeding causes the message to go away but lights still done work.

Have you solved your problem yet?

[PainterPaul]

Brake switch is working cause the 3rd brake light comes on.

[June]

Hi
Mechanic changed the cable and 1/2 the fuse box. It too had melted.
He complained about the 5 feet of wire snaked all through the engine.

Thanks for your help

I'm glad my experience with my car was able to help.

You might just need to get a dealer to plug your car in. Perhaps the software is corrupt somewhere causing your brake message? These cars are a rolling computer system. June

[MoVolvos]

Do you think that might be causing the
battery drain and
the driver seat forward and back control from not working too?
All the other controls seat controls work.

Looks like the fuse box and cable failed at 134K on my car.

June

December of last year the 03 S80 T6 was slow for a moment and didn't turn over. Did start eventually and never happened again. Purchased a battery from Costco but got busy and forgot about. Eventually saw the battery sitting and remembered the problem but returned it after it never repeating itself.

This post had me going for a moment because the car is around that mileage. Checked the Post today and it looks normal. Hope it will stay that way.
.