Car wouldn't start, changed battery all ok, but...

[Pazza]

OK, so I had noticed for a while that when starting the car, it was not turning the engine over with the expected urgency, but always started ok. Restarting after a good journey was fine, and sort of implied to me that the alternator was doing its job. In the recent cold weather it was doing the same and there were a few very cold mornings where the Power Steering light was stuck on, and stiff steering, but a run and restart got rid of it. Then the car was stationary outdoors for 5 days before I used it again, and when I tried to start it, there was absolutely nothing - no fuel pump sound, no glow plug lights, central locking was clicking, clock/mileage displays were going funny. So, I thought battery dead, and fitted a new one, and it started no problem.

However, I measured the old battery tonight, and got 11.55V unloaded across the terminals, which seems to indicate all cells are ok. Also unscrewed the inspection window, and the ball thingy (technical term) is green, so it would appear ok. I know loaded is a different scenario, and voltage doesn't mean current is being drawn, but it got me thinking if there is really another problem. I have seen other threads regarding broken alternator cables to starter motor etc, but not really sure if this is something I could have? I have no ideas where the alternator is to know what I am looking for.

Car is 2003 Ibiza 1.9TDi SE

 

[Pazza]

Just checked online - 11.55V unloaded indicates a fully discharged battery.
and the acrylic "eye" actually had the green float at the bottom, and a blackened window, so I can now say it really is a dead battery.

Whether or not another issue contributed to this, is to be confirmed...

 

[mexicorich]

Measure the voltage at the battery terminals with the engine running
Should be close to 13.8V
Start the car without revving the engine, just let it turn over and tickover
If the alternator lead has snapped, the alternator won't kick in until the engine is blipped past 2.5 - 3k revs and you will just get a 12v reading from the battery

 

[Pazza]

Measure the voltage at the battery terminals with the engine running
Should be close to 13.8V
Start the car without revving the engine, just let it turn over and tickover
If the alternator lead has snapped, the alternator won't kick in until the engine is blipped past 2.5 - 3k revs and you will just get a 12v reading from the battery

so basically, if I measure 13.8V after starting, all is ok, but only 12V there's a problem? If I get 12V and rev past 3000rpm, should I see it rise to 13.8?

 

[mexicorich]

You should get 13.8V engine running but without having revved it at all, just letting it tickover straight from starting.
If it is 12V (ie not charging) and only rises to 13.8V when the engine has been revved past 2.5 - 3k once, then the load sensing wire from the alternator has snapped

 

[Nath.]

A slow starter motor could be a poor battery connection, resistance across the battery connections or a poor earth lead connection to the chassis can cause low voltage to the starter and make it slow.

 

[Pazza]

OK, so forgot to put an update on here..

So I measured the battery voltage loaded and it was 14.5V (without touching the accelerator), so I guess this concludes that the load sensing lead is ok.

It is still a bit sluggish on start, but the car can be left unused for a few days at a time (due to life sharing) and the general low temperatures of late, so hopefully it's just this, but I guess I can't rule out another poor connection to the starter motor?