Afternoon, all. I looked back a few months and searched about this but only saw one reply two years ago that sounded like my issue and no one answered. Sorry for the long story, but I would appreciate anyone who reads it all and offers some advice.

Here's the story: I have a 2002 Cooper r50. Everything is completely stock, no mods at all. A few months ago I noticed that sometimes when I would get in the car the electrical system seemed to have reset. That is, the clock was different; the displays like DTE, average speed, etc were all reset; and the CD in the radio was back at the first track even if it had been in the middle of (for example) the 8th song on the disc. Sometimes I'd shut the car down and the central locking system wouldn't work immediately (to either lock or unlock) but after a few minutes it would be fine.

Then a few weeks ago I shut the car off, got out, realized I had forgotten something and had to head back home and the car wouldn't start at all. Total time between shutoff and trying to start again was probably less than a minute. After I hemmed and hawed for maybe five minutes, I tried starting it up again and it worked fine, started right up with no hesitation. Electrical system had reset again. We drove it around yesterday for probably 15 miles and when my wife got in this morning to go somewhere, it wouldn't start at all. When turning the key she got nothing, no clicks, no attempt to turn over, nothing.

One other interesting issue: When idling at stops, when the A/C is running, the car will start to die and all the electrical systems will shut off for a split second. The radio cuts out completely, the A/C shuts off, but just for one half a second then it comes back on. This only seems to happen when the radiator cooling fan kicks in. We've had issues with it before, it has been stuck on to the point where you have to pull the fuse. That all seemed to stop and the fan has been running fine, although it did cycle a bit.

Is it possible that the radiator fan is bad and is causing such a pull on the electrical system that eventually it drained the battery? Could this be as simple as replacing the radiator cooling fan? I know my accessory belt is a little worn but it hasn't really been making any noise. Could this be an alternator issue?

Thanks in advance for any words of wisdom.

 

I would say battery issue to start, then look into the alternator. Basically sounds like the battery is not receiving enough juice to keep all the power running at the same time. All electrics draw from the battery (which is in turn charged from the alternator) so a faulty battery would show these signs as well as a faulty alternator not able to keep up with the demand of the car. If you've never changed the battery, it's definitely time to do so. When the radiator fans kick in, it draws more amps starting the fans than while turning so your battery is probably charged enough by the alternator to be right at the breaking point. The other possibility are the cables, but I'd target the alternator and battery first. Get an electric tester and check out the battery and the power from the alternator to see if they are within spec or not.

 

Thanks, proximo. That all does make sense. I'm sure the (probably) bad fan isn't helping matters any, but testing the alternator and battery are easy to do.

 

I would look at the connections where both the ecu and bcm plug in...check they ate both toght and corrosion free....
Generally i would then try ro inspect the bulk of the wires (the wiring harness) for chafeing/cuts...maybe if you can start the car, wiggle the wires, see if it makes the symptoms reoccur....
A failed fan would result in just overhearing, or maybe ac issues (lack of cool air when not moving, possible longer term compressor failure) but would not result in the car's electrical system failing.

 

P.S
Also chck the ground connections for the battery and the motor...the motor to chassis ground is by the engine mount....not sure which others are around, but corrosion or a chafed ground wire could cause some odd things to happen.

 

Thanks again to everyone for the ideas. I wanted to follow up with the outcome of this issue. I'm a little surprised that my minimal mechanics skills were able to solve what turned out to be an incredibly complex problem. You'll all be stunned by what I had to go through to get it fixed:

The positive wire to the battery was loose. :~)

My father-in-law came over with his battery charger and we were expecting the worst. Open up the hood, put the multimeter on the battery and were very happily surprised to see that it read 12.7 volts. The battery terminals looked in pretty good shape but of course we decied to give them a good scrubbing anyway. When I reached down to loosen the positive cable, well, I didn't need to loosen it at all, it practically came off. Tightened that bad boy up, turned the key and it started right up. *sigh*

Wire brushed both terminals anyway, tightened them both up again and started everything back up. Put on all the accessories I could (max A/C, radio, lights, etc) and waited for the radiator cooling fan to come on. Fan came on, no dip in the engine and no cutout of the electrical systems in the car. It hasn't been driven around town in the heat of the day, but I'm expecting that this solved most of the issues we've been having (except for the bad fan, of course).

I am obviously very happy that the solution was about as simple as it could be, but frustrated that I got so worked up over nothing. Oh well. Learning experience!

 

It's always nice when it's an easy fix. You were right on target with a wiring issue. A bad battery or weak alternator would drain the battery to the point where it would need to be jump started. Waiting 5 minutes then it restarting gives a clear indication that the alternator and battery are fine. I wonder when the last time you worked on the battery was, how long that thing was loose for?? lol