Electrical problems with Z4 3.0si roadster

[Ant]

Hi All, Have recently returned from a 600 mile round trip and experienced the following problems with the car:
After approx 3 hours driving the red battery light illuminated on the dash and the power dropped away from the car. It pretty much instantly returned and then repeated itself for a minute or two. I pulled over, switched the engine off then restarted and found that I'd lost power steering (it was also difficult to start). Switched off, restarted and power steering was back. Continued journey for about 30 minutes then had an hour and a half break before continuing with journey - no other problems occurred.
On the return journey the exact symptoms were experienced approx around the same 3 hour point of driving; loss of battery power, loss of power steering, difficult to start and all the corresponding lights illuminating on the dash. Stopped for approx 30 mins and for the next two hours of driving the car was trouble free. I've checked battery connections, battery condition (I use a CTEK trickle charger when she's not in use), have used a meter to check the state of the alternator and all seems fine. I've had a cursory check of wiring in the engine compartment and all seems okay. No overheat warnings during driving.
Since returning home have been out on short 30 minute drives and no problems with the car at all. Grateful for any thoughts on what might be the problem.

 

[GazHyde]

Which Z4 do you have Ant? E85/6 or E89?

 

[GazHyde]

No worries, just saw your intro thread where you say you have the same as me - a 3.0si. Only obvious thing I can think of would be the actual battery itself. Any idea how old it is? Just had to replace my battery a few months as it was the original and 10 years old.

 

[t-tony]

Hi Ant, the vast majority of these problems we deal with at work turn out to be the battery. If yours is the original, I would definitely carry out a heavy amp. drop test if you can find someone who still has one (rare thing these days) as these sort out a duff battery quite quickly. Otherwise if you have no history of it being replaced, that is what I would do.

Tony.

 

[Ant]

Which Z4 do you have Ant? E85/6 or E89?

That is a very good question. I can't find anything in the paperwork that mentions the type of engine. I do know that it was one of the first models to come out in early 2006 (first registered in Mar 06). I believe the engine was changed to conform with EU emissions regs.

 

[Ant]

No worries, just saw your intro thread where you say you have the same as me - a 3.0si. Only obvious thing I can think of would be the actual battery itself. Any idea how old it is? Just had to replace my battery a few months as it was the original and 10 years old.

The battery is only a couple of years old and I've been using a CTEK charger to keep it in tip top condition.

 

[GazHyde]

If it's the 3.0si then it's an E85 if Roadster or E86 if it's the Coupe. The E89 is the later design with folding tin top.

 

[Ant]

Hi Ant, the vast majority of these problems we deal with at work turn out to be the battery. If yours is the original, I would definitely carry out a heavy amp. drop test if you can find someone who still has one (rare thing these days) as these sort out a duff battery quite quickly. Otherwise if you have no history of it being replaced, that is what I would do.

Tony.

Thank Tony. I changed the battery a couple of years ago. Perhaps this one is now duff too? Bit of a short life span, particularly as I've been keeping it trickle charged when car not in use. Thanks for the advice.

 

[Ant]

If it's the 3.0si then it's an E85 if Roadster or E86 if it's the Coupe. The E89 is the later design with folding tin top.

Got it. Must be the E85. Another day learning something new!

 

[t-tony]

Always a chance that a mass produced item could have a cell down mate, and this all it would take. A drop tester when placed across the terminals is basically a dead short and if a cell is faulty, with the cell tops removed, you can see the electrolyte bubbling. If the battery is only 2 years old it could quite likely still be under warranty too, many have 3 year warranty so worth looking into!

Tony.

 

[Ant]

Always a chance that a mass produced item could have a cell down mate, and this all it would take. A drop tester when placed across the terminals is basically a dead short and if a cell is faulty, with the cell tops removed, you can see the electrolyte bubbling. If the battery is only 2 years old it could quite likely still be under warranty too, many have 3 year warranty so worth looking into!

Tony.

That's great. Thanks very much. I'm on it. A duff battery would be the ideal solution to what I thought might be a major problem. Cheers again.

 

[t-tony]

Hope it turns out to be that Ant.

Tony.

 

[Ant]

Hope it turns out to be that Ant.

Tony.

Any advice on a decent replacement Tony? Also, I should have mentioned that sometimes when I first turn the ignition key all I get is a click. After a couple of goes she fires up no problem. Is this another indicator of a duff battery perhaps?

 

[t-tony]

Any advice on a decent replacement Tony? Also, I should have mentioned that sometimes when I first turn the ignition key all I get is a click. After a couple of goes she fires up no problem. Is this another indicator of a duff battery perhaps?

Yes it is, however worth checking the main battery lead connections at the starter motor, and engine to body earth cables too. Another possibility is a "dead" spot on the starter motor armature. All the above are not helped by a weak battery too, so that's where I would start.

Tony.

 

[Ant]

Yes it is, however worth checking the main battery lead connections at the starter motor, and engine to body earth cables too. Another possibility is a "dead" spot on the starter motor armature. All the above are not helped by a weak battery too, so that's where I would start.

Tony.

Thanks, you've been a great help. Will let you know how I get on.

 

[t-tony]

You're very welcome mate.

Tony.

 

[Redline]

Unusual for everything to seem fine and then the voltage to suddenly decay after a period of time. That sounds like it could be a number of things.

Got to ask what could cause the car to run for some while then the battery charging stop. Could be the alternator is trying to charge into a high load, and, after some time, simply failing causing a charging failure. The battery is then sinking the load entirely.

The high load could be the battery itself but could be a number of other things too.
I'd get the battery and the alternator properly tested for starters. If it is intermittent and taking a while to happen it might be difficult to isolate.
A battery change might solve to but it might be a fault elsewhere.

 

[Ant]

Unusual for everything to seem fine and then the voltage to suddenly decay after a period of time. That sounds like it could be a number of things.

Got to ask what could cause the car to run for some while then the battery charging stop. Could be the alternator is trying to charge into a high load, and, after some time, simply failing causing a charging failure. The battery is then sinking the load entirely.

The high load could be the battery itself but could be a number of other things too.
I'd get the battery and the alternator properly tested for starters. If it is intermittent and taking a while to happen it might be difficult to isolate.
A battery change might solve to but it might be a fault elsewhere.

Thanks for this. It's really weird right? I'm also of the opinion that it could be something bigger than just the battery (but hopeful that it is nonetheless). My problem would seem to be trying to replicate the issues in a garage that'll run the engine for a while and see nothing happening. I assume only a garage can properly test the alternator and battery?

 

[t-tony]

Do you have a voltmeter to hand, if so you can test the alternator output easily enough. Run the engine at idle with no electrical load switched on, connect the positive lead to the main cable terminal on the back of the alternator and the negative to earth. Note the voltage reading (looking for near to 13.8v). Now run the engine at idle and load up the alternator by turning on electrical load, HRW, headlights AC, heater blower on full etc. and note the voltage reading (it will probably have dropped slightly to around 12-12.5v), then get someone to increase the engine speed to fast idle (2,000 rpm.) and watch the voltage reading, it should increase and go back up to the level shown at idle with no load or slightly higher. You can do this test at the battery terminals but doing it this way ensures a true reading direct from the alternator.

Tony.

 

[Ant]

Do you have a voltmeter to hand, if so you can test the alternator output easily enough. Run the engine at idle with no electrical load switched on, connect the positive lead to the main cable terminal on the back of the alternator and the negative to earth. Note the voltage reading (looking for near to 13.8v). Now run the engine at idle and load up the alternator by turning on electrical load, HRW, headlights AC, heater blower on full etc. and note the voltage reading (it will probably have dropped slightly to around 12-12.5v), then get someone to increase the engine speed to fast idle (2,000 rpm.) and watch the voltage reading, it should increase and go back up to the level shown at idle with no load or slightly higher. You can do this test at the battery terminals but doing it this way ensures a true reading direct from the alternator.

Tony.

Thanks Tony. I've done this test from the battery but not from the alternator. Will give it a go. Cheers, Ant.