Possible upcoming alternator replacement

[unluky]

I always winter the Z in my building. It is not climate controlled, but it stays "comfortable" in there and I have not had any issues in the 5-6 years I have owned it. I go start it once a month or so, rock it back and forth some to keep the flat spots on the tires away - and if we get an Indian summer day in there - she goes for a 8-10 mile drive here and there usually.

Never use a battery maintainer before, but I have a few and one of the cars I always used one on went down the road so I put that one on my Z4 this winter and connected it under the hood. I charged up and showed full and all was well. One of those nice days came along and I fired her up and headed for the highway for a cruise. Fired up perfectly and away we rolled......but......about 1/2 mile up the road my dash lights light up like a xmas tree and my power steering konks out. Car is still running perfectly, but crap is getting real. climate lights going on and off, etc. Everything is working - just elec stuff going wonky.

Turn around and drive home with no issues, but in the garage I notice when I rev the car - the "problems" change. Some lights come back on, some go back off and switch when I idle or rev a little.

I shut her down, disconnect the battery and test it - shows fine. I connect the charger to it for a day then the maintainer for a week or so after - battery acts perfect and test perfect. Reconnect everything and she fires right up - but same things happen.

From my research - I am guessing belt, belt slipping, alternator, volt reg - or a combination of these.

Does that sound right or am I off base? With the steering going out and elec issues I was suspecting a belt/tensioner since I believe they are on the same belt (need to look).

I'm usually a "if i'm in there, change it" guy, so if I dive into this I will probably change it all while I am in there. Not going to do all that and change a volt reg on an old alt just to save $150 - to find out I have to go back in. I just want to make sure I am on track with my thinking before I dive into this. Does not look like a terrible job.

2004 Z4 3.0 M54 - as far as I know - belts/tensioner/alternator are all original. Bought the car with 60K and now I am at 95K, so not a shocker.

Missing something? Anything else I should do when I get in there?

[elerner61]

I'd agree that voltage regulator (or entire alternator if you'd like) is your next stop as long as you're sure your battery is good (and perhaps not showing some possible age related aches and pains). If changing the battery is on your "to do soon" schedule (everyone's different) you could do that first to remove one component from the equation.

[unluky]

Originally Posted by elerner61

I'd agree that voltage regulator (or entire alternator if you'd like) is your next stop as long as you're sure your battery is good (and perhaps not showing some possible age related aches and pains). If changing the battery is on your "to do soon" schedule (everyone's different) you could do that first to remove one component from the equation.

Well - I am fairly sure, it test fine and all that. Perhaps I should pull one from another car to put in there to make sure. I hate to buy a new one as this one is not that old and tests fine and spins it like a top, but I sure would be pissed to replace all that and find out it was the battery all along.

Free to do that and I have one in one of my SUV's that I put in just a few months ago, so I will take a look at that and see if I can drop it in for a sec and see if that changes anything.

Measure twice cut once right? Good call - I'll give it a whirl.

[unluky]

OK - the plot thickens....

The other newer battery I have I took out, but of COURSE the posts were reversed. So I put it behind the trunk and used jumper cables to attach to the posts and the connectors in the Z (other battery unhooked). Would not even start the car. Loss in cables, whatever, but would not work. So I hook back up the battery in the Z, attached the jumper cables to the other battery and to the cables in the car (both batteries hooked up) and left the trickle charger on and running - remember - the old battery always started the car just fine - not even a hesitation.

So I start the car - runs fine....for a few minutes like always then the PS lite comes back on then they slowly all start coming back on - and the dash lights go on a off etc - same old same old.

So then I wanted to take the battery out of the loop - I unhook the other battery and the trickle charger, cars still running fine. Unhook the battery in the car - car is still running fine with no battery - alternator is powering it alone. Let it sit a sec and get in the car - dash the same - lites everywhere, then I give it just a bump on the throttle and it stumbles just a sec. I bump it again it stumbles, sputters and dies. Everything dead.

OK - sounding more like the ALT now right - Hook the battery back up in the trunk - fire it up - it hums like a top - but no dash warning lights. I go put the battery back in the SUV and come look again - no dash warning lights. I go start the SUV to make sure all is well and let it run a few minutes - tighten connections all that go back and check - still not dash warning lights and I still have power steering. WTF?

I get in and goose the throttle - all good. Radio is playing, headlights, blinkers, fogs, power windows, etc all working fine. I drive the car 10 feet to the front of the garage and reverse it back - rev to 3-4K - nothing - just like old times. Like it never happened.

I am home alone tonight, so don't want to risk a drive and get stranded, but seriously - what the hell?? Still feel like since it died with the battery out of the loop I could have an issue with the alternator/regulator. Belt seems fine and no noise under the hood - but that does not mean anything.

The search goes on - I will have to take her out for a drive soon and see what the hell is going on. Feel like it dying without the battery makes my test of the battery seem valid???