2005 X-Type
About 50k miles
Automatic

It's my mom's car. This apparently happened once in a parking lot. My father was sitting in the car messing with the radio and all of a sudden all power in the car was lost. Like there was no battery in the car. After about 40 minutes of waiting for the tow truck it started up again like nothing was wrong. Tow guy checked the battery and it was fine. Parents thought it was alarm related and because my dad was messing with everything while my mom was shopping, so they never mentioned it to me.

Yesterday, while driving on the freeway, my mom reported that all the dash lights came on and the car shuddered, then the lights all turned off and the car was fine. She tried nursing it home, but a few miles down the highway all electrical turned off and she coasted to the shoulder. Not even the hazard lights worked.

Car was towed to a mechanic's shop and they just called me to report: car was pushed into garage last night but driven out this morning. NO codes on the computer. Alternator on the lower end of spec. Wire secure. Battery good, wires tight. He doesn't know WTF and isn't even going to charge me diagnostic time. Says he suspects either something in the ignition, a bad relay, or bad ECU...but he isn't sure enough to actually recommend a repair because it would be a guess and just blindly throwing money at the car.

The thing that gets me is that when the failure happened, there is NO power. That suggests to me that it's possibly a bad ground wire or connection or bad power wire or connection? A relay or ECU failure wouldn't explain why even the hazard lights wouldn't come on? It's like someone pulled the battery.

BUT, at freeway speeds, even if you pull the battery, shouldn't the alternator still power the car enough for it to keep running? The mechanic threw out a number that I don't recall right now, but under load, the alternator was at the lower range of accectable spec. 13.1V? Something like that?

Any help would be greatly appreciated. I'm not comfortable with my mom driving the car until the problem is solved. Many thanks in advance!

 

Stanae86, based on what you are describing, you have a bad ground wire between the body of the car and the battery. That will kill all the power to the vehicle and it will go away once things cool off a little bit (wiring will get more resistive the hotter it gets, leading to lots of voltage loss and a "powerless" car). What I would tell you to do is to hand over hand the ground wire to the car and look for any spots where the insulation is cracked or crumbly. That would be signs of heat damage. If the connectors look dark and crusty, another sign that they have gotten hot. We can be talking about something as small as 0.1 ohm here, which is very little resistance. You will also want to check the wiring between the battery and the fuse box. That wire can cause the same symptoms.

If you know how to use a multimeter, that would also be helpful as you can put the multimeter on the VDC scale and run the leads from one end of a wire to the other (ie, black lead on one end, red lead on the other end). If you are seeing anything over 0.5 VDC drop across a wire (especially the ground wire), there is your problem.

As for the alternator output, yes, that is low, but not fearful. This may be one of those things that if you can fix the problem with the power completely fading away, that voltage will come back. The alternators in our X-Types are pretty stout things and failures in them are rare.

 

Thanks for confirming one of my suspicions.

I'm going to ask the mechanic to change the negative and positive to the fuse block before I pick up the car. Then it'll just be time and seeing if it happens again. Thanks for your detailed explanation, I really appreciate it. I'll see if I have a friend with a multimeter that might be able to check the old wire's resistance also, but at the very least, I'm going to hawk-eye the thing and see what kind of condition it's in.

Wish me luck! Thanks again!

 

stanae86, when doing the checks of the wiring, try to turn on everything possible that is electric in the car. Turn on the dash fan on high (manually), high beams on, turn on the seat heaters, etc. With the dash fan, seat heaters, and lights, you should be up around 100 amps load on the alternator and wiring. If you are going to see a problem, it will be at that point. Do not be surprised if you find a new "light bulb" under the hood of the car. I have seen where a wire was failing in my car and when I did this, the wire started glowing white hot. Needless to say, a big pucker factor happened. Atleast I found the fault. Too bad that wire was right behind the carburetor and next to a gas line.

 

Which wire was it for you?

I'm just having the shop change the power wire to the fuse block ($160 special order from Jag) and I'm having them change the negative wire as well. I'm having them save the wires for me so I can look at it and hopefully test it with a friend, but I figured I might as well do it since it's in the shop and it sounds like a possibility (more than a relay or ignition problem or something like that).

Thanks so much for your help Thermo!