This 2004 Volvo XC 90 T6 AWD came in with the complaint that the battery would go dead overnight. Sometimes it would go dead while the customer was at work.
The battery is located in the rear of the vehicle under the floor. At the tailgate there is a removable floor panel that covers this steel panel. Two bolts and one nut, all 13 mm.
Now a plastic cover has to be lifted away.
At the negative battery terminal I loosened the 10 mm nut and slide the terminal slightly up, so that I could connect one lead of my multimeter to the battery post and the other to the cable terminal.
After the leads were secured I lifted the battery cable and terminal from the battery post. Making sure to keep the connections with my multimeter intact.
One lead of my meter is connected to the COM port and the other to the 20A port. The dial is set to DC amps. Of course all leads were properly connected to the battery terminals and the multimeter ports before I separated the battery terminal from the battery post. Well with and amperage draw of almost 8 amps it is easy to see why the battery goes dead.
After a minute or two the amperage draw went down to about 4 amps.
After about 5 minutes the draw went down to about one amp. and stayed there.
While the amperage was high I circled the vehicle, looked and listened. I found that the vacuum pump located behind the driver’s headlight area was running. I am pointing to it the the next picture.
I did not see a listing for the vacuum pump in the underhood fuse box so I looked at the legend for the fuse box located at the driver’s side end of the dash. I found that the power steering and the vacuum pump are both powered by fuse #16. I took the liberty of looking at a wiring diagram to see where fuse #16 receives it’s power from. I noted that fuses 16 and 17 are both supplied power from the Overload Relay 15-Feed.
I checked and fuse #17 has power on it when the key is off.
Fuse #16 also has power on it with the key off. I make the point of showing the key with power present because the relay that supplies power to the two fuses is controlled by the ignition switch. In other words there should only be power on these two fuses with the ignition key on and the relay working correctly. Key off turns the relay off and cuts the power to the two fuses.
The relay is located behind the driver’s side of the dash. There are two torx screws that have to be removed from the underdash hush panel.
The panel will then unsnap and pull down from the dash. The small closeout at the OBD2 connector also has a spring clip and plastic retainer that have to be dislodged as well.
There are two load carry relays in the electrical center under the dash and I decided to replace both at the same time. The relay I knew was faulty is the 15-Feed Overload Relay. The other relay is the X-Feed overload Relay.
Both relays are shown at the upper left side of the next picture. Counting from the top left of the box and going straight down, the first position is empty. The second position holds the X-Feed Overload Relay and the third position is where the 15-Feed Overload Relay is located. By the way when I started to remove the relay it clicked off and the drain was gone. The contacts had been stuck closed.
Now there is no power on fuse #17.
No power on fuse #16 either and of course it should not be as the key is in my hand.
The battery drain is down to a more than acceptable .01 amps.
If the X-Feed Overload Relay had been stuck on fuses 8, 9, 10 &11 would have had power on them at all times.