Intermittent death - lots of potential causes checked

[Foeux]

Originally Posted by Ian21401

Foeux,
I’ve been following this thread and it has me intrigued.
Just a few thoughts from an outsider. Feel free to ignore them if you wish.

Post #26, When you first tried the engine would not turn over. Did you check the battery voltage before you tried to start the engine? To try to establish whether the battery voltage was already too low, or 1) it suddenly dropped once the ignition was switched to position 1, or 2) it suddenly dropped when the switch was in position 2, or 3) it suddenly dropped when the starter motor was trying to turn?

Once started using a jumper battery the alternator is charging.
I understand that you then disconnected the jumper battery?
and then after a few minutes of running on it’s own battery the engine dies?

You mention that the charge rate was dropping after the engine stopped.
As the engine was now stopped there would be no charge from the alternator so, do you mean the battery voltage was dropping?

Is it possible to state what the battery voltage dropped to before you switched off the ignition?
Yet, when you switched off the ignition the battery voltage returned to 12.24 volts.
Given that the engine would not turn over when first tried this morning. Is it possible once the engine has been running then died to check the battery voltage periodically to establish at what rate the battery voltage drops?

Batt voltage before trying the starter was 12.2#v but it drops like a stone as soon as you try to turn engine (and even before) with ignition in pos 2. Drops to a stable 9.5v then as soon as you crank you are dealing with 5v or less.

Battery restores voltage to 12.3ish over a few hours of waiting with ignition off.


Once started using a jumper battery the alternator is charging. Yes.
I understand that you then disconnected the jumper battery? Yes
and then after a few minutes of running on it’s own battery the engine dies? Yes...sometimes. sometimes fine. Sometimes rough running, misfires and engine death. Rapid discharge to 9.5v.


You mention that the charge rate was dropping after the engine stopped.
As the engine was now stopped there would be no charge from the alternator so, do you mean the battery voltage was dropping? Yes. I apologise for being confusing.


Once engine dies but ignition left on, voltage drops quickly (inside 1 min) to about 9.5v. Once ignition is off and battery left for a few hours, it is healed back to 'normal 12.3ish.

[Ian21401]

Foeux,
Have all the leads had a voltage drop test whilst under load. I don’t know a lot about such things, but after having a trawl around UTube I think that it is worth doing.

Bob,
I believe that the Bosch Silver battery on my 940 may be calcium (I’ll try to check) The charge rate when running normally varies between 13.2 and 13.8 volts.

[Laird Scooby]

Originally Posted by Ian21401

Foeux,
Have all the leads had a voltage drop test whilst under load. I don’t know a lot about such things, but after having a trawl around UTube I think that it is worth doing.

Bob,
I believe that the Bosch Silver battery on my 940 may be calcium (I’ll try to check) The charge rate when running normally varies between 13.2 and 13.8 volts.

Ian - the OP has confirmed the battery isn't taking a charge using separate chargers. As i understand things, he's already had those (oer similar) checks done by whoever remedied some apparently intermittently bad connections.

The Bosch Silver range of batteries eg S4005 and similar are all Silver-Calcium technology and ideally should be charged at a higher voltage.

A charging voltage of 13.2-13.8V is too low, if you're not experiencing problems even with a normal battery, either your voltmeter is reading too low or you have a dormant problem waiting to catch you out.

[360beast]

My 940 has been charging about 13.2v for a few years and it has been fine up to a point, if I left it for a couple of weeks the battery would go flat. In the end I decided to pull the alternator off about 2 months ago and see what I could find wrong with it. I found that one slip ring was incredibly warn and the other a little worn, the carbon brushes were also unevenly worn so one was almost non existent and the other barely worn.

So I looked at my two spare alternators, one had heavy wear on both slip rings and the other turned out to have been refurbished! I thought I'd struck lucky so I fitted the refurbished item and checked the charge rate and it was 14.2v. so the next day I went for a 150 mile drive to pick up the new family car and on the way back I could hear a strange noise, we pulled over at the services for some lunch and I found that the bearing had become very noisy on the alternator. I switched it off and went for some food, about 40 minutes later when I went to restart it it struggled to start and took multiple attempts to start which it has never done before. When I got home I checked the charge voltage and it was fluctuating between 12.9-13.0v. back on the original alternator went but using the voltage regulator from the "refurbished" one and it now charges at 14.2v and drops to 13.8v when everything is switched on full. but I'm still left with the issue of one very worn slip ring, so I will have to replace the slip rings at the very least some point soon.

I now no longer have any issues with the battery going flat if left for a couple of weeks, I would suggest that if your alternator is charging at 13.2v Ian then it might need a new regulator pack and I would inspect the slip rings while there.

It might be something useful for you to check too Foeux, I doubt it is the source of your issues but it could be a contributing factor.

[Foeux]

Originally Posted by 360beast

My 940 has been charging about 13.2v for a few years and it has been fine up to a point, if I left it for a couple of weeks the battery would go flat. In the end I decided to pull the alternator off about 2 months ago and see what I could find wrong with it. I found that one slip ring was incredibly warn and the other a little worn, the carbon brushes were also unevenly worn so one was almost non existent and the other barely worn.

So I looked at my two spare alternators, one had heavy wear on both slip rings and the other turned out to have been refurbished! I thought I'd struck lucky so I fitted the refurbished item and checked the charge rate and it was 14.2v. so the next day I went for a 150 mile drive to pick up the new family car and on the way back I could hear a strange noise, we pulled over at the services for some lunch and I found that the bearing had become very noisy on the alternator. I switched it off and went for some food, about 40 minutes later when I went to restart it it struggled to start and took multiple attempts to start which it has never done before. When I got home I checked the charge voltage and it was fluctuating between 12.9-13.0v. back on the original alternator went but using the voltage regulator from the "refurbished" one and it now charges at 14.2v and drops to 13.8v when everything is switched on full. but I'm still left with the issue of one very worn slip ring, so I will have to replace the slip rings at the very least some point soon.

I now no longer have any issues with the battery going flat if left for a couple of weeks, I would suggest that if your alternator is charging at 13.2v Ian then it might need a new regulator pack and I would inspect the slip rings while there.

It might be something useful for you to check too Foeux, I doubt it is the source of your issues but it could be a contributing factor.

Thanks very much for the input.

Is the check on the regulator a visual/physical inspection or can I prod at it with the multimeter to determine if it is goosed?

New batt today. If it shows off hereafter and I resist the temptation to throw it into the nearest body of deep water, I will get on with the alternator checks etc.

[360beast]

Originally Posted by Foeux

Thanks very much for the input.

Is the check on the regulator a visual/physical inspection or can I prod at it with the multimeter to determine if it is goosed?

New batt today. If it shows off hereafter and I resist the temptation to throw it into the nearest body of deep water, I will get on with the alternator checks etc.

You need to remove the regulator to do a visual inspection of it and the slip rings

[Ian21401]

Dave,
Your points accepted. The battery was new March’18. Bosch Silver 096 S5 008 780A(EN) 77Ah. I cannot find any indication anywhere on the battery that it is calcium, but I accept that it very probably is. It replaced a Bosch Silver HN which had been fitted since April ‘06. (12 years).
Thanks Luke,
My alternator is an 80amp of unknown age. It is a previously used one of two that I obtained from a forum member back in 2012 when I was trying to locate the source of a rhythmic noise apparently from the aux. belt area and I suspected the bearings of the original alternator. (it wasn’t the alternator bearings ). I’ve been meaning to check the slip rings etc. for some considerable time but simply have never actually got around to doing it. I think that I will try to find the time to check the other one once I’ve done the cam belt, aux belts and oil and filter change which are overdue.

[Foeux]

Originally Posted by Ian21401

Foeux,
Have all the leads had a voltage drop test whilst under load. I don’t know a lot about such things, but after having a trawl around UTube I think that it is worth doing.

Bob,
I believe that the Bosch Silver battery on my 940 may be calcium (I’ll try to check) The charge rate when running normally varies between 13.2 and 13.8 volts.

I have not personally drop tested every lead but may have to learn how. Sort of relied on the garage that charged me for 'fixing the problem' having done that...

[Foeux]

Originally Posted by 360beast

It might be something useful for you to check too Foeux, I doubt it is the source of your issues but it could be a contributing factor.

Can this be done in situ or is it an alternator off job?

[Foeux]

Now for the big update.....

Yesterday's search for the stolen battery in Halfords was fruitless.

Today I checked with a garage that they had lead acid, non-calcium batteries. They did, gave me a price, went to collect. The battery had the word CALCIUM emblazoned across the front.

I was told to use it anyway. I did not buy it. Felt a bit of a twunt refusing a brand new battery and there is very little actual help available out there in the real world.

Have rung around and been told everything from:
'They are illegal now, mate...'
'Nobody makes them any more...'
'There is absolutely no difference, they are more modern and better, you shouldn't be using old fashioned technology any more, mate...'
'They make the engine run more efficiently so you should buy one...'
'There was an old boy that ran a 940 for ages and had an intermittent fault. He tried to fix it for two years and ended up scrapping it. Hates his new car...'
'Of course they are lead acid. There no calcium or f*****g milk in them.'

So, here I am. Still no battery. Still driving on eggshells so to speak as I fear it will do me a disservice again.

I've put a checked good battery in for now.

I will source a lead acid one from the British Museum or wherever actually has them.

I will have a look at the reg on the alternator and I will keep thoughts of the scrap man at bay.