Won't start, won't turn over

[RealEstate]

My '91 945 230FB is having her annual paddy! Was running fine three days ago.

Today she won't start or even turn over.

The battery voltage is 11.0V. Voltage at red cable on starter motor is also 11V. When I turn ignition key to position II, the warning lights light up and the fuel pump runs as expected. However on turning the key to posit III (start) there is a slight click and the warning lights dim a little but nothing more. Starter doesn't turn.

Then I disconnected the blue/green wire from the starter and attached my volt meter to it. With the key in posit II, the voltage on the blue/green wire reads ~7V. When the ignition key is turned to posit III, it increases to about 8.5V.

(photo courtsey of Old BlueVolvo!)

Perhaps I should have measured the voltages with the blue/green wire still connected?

I'm charging up the battery overnight. Any suggestions appreciated!

[OldBlueVolvo]

A 12V car battery with a terminal voltage of 11.0V - is a dead battery. It has discharged for a reason. Either it is faulty (most likely) or there is some other problem. I wouldn't worry about the voltage on the blue/green wire until you know that the battery is OK. HTH.

edited...
Hmm.. I've just been thinking! 7.5V on the blue/green wire when it should be 0V. Out of interest, leave that wire connected to the starter and test the voltage without cranking. It should be 0V.

[CTCNetwork]

Hi,

Or perhaps the starter is jammed? Tried popping her in gear and rocking back and forth a little and trying then?

Des. . .

[OldBlueVolvo]

Originally Posted by CTCNetwork

Hi,

Or perhaps the starter is jammed? Tried popping her in gear and rocking back and forth a little and trying then?

Des. . .

That's interesting. If the starter was 'jammed' would it cause the battery to drain? I remember when my aerial used to jam it would cause the fuse to blow (so excessive current).

[CTCNetwork]

Hi,

I've had a jammed started a couple of times, the car rocking process got me out of that issue.
I never considered voltage or battery condition when it happened (a good few years ago now) so can't comment on the possibilities of battery drain.
Would depend on whether the starter stayed in open circuit I suppose when the ignition was turned off, no?

Des. . .

[RealEstate]

Charged up the battery overnight, now holding over 12V. Tried to start her.

But on turning key to posit III (start) there is a loud buzzing noise I think from the starter or solonoid...?

Called the RAC for my 'annual' rescue as I'm away from home.

Unfortunately she's an auto so I can't be sure the starter isn't jammed, but no reason to suppose it is.

Will report back.

[pdrvolvo]

as said before 11v might aswell be 2v for what good it is.a good battery will stand at 12.5v for months.as you crank the engine it should not drop below 10v and as she fires the voltage should rise to between 13v and 14.5v approx. as the chargeing system takes over.a low battery will give the "machine gun" effect i.e. as the key is turned the starter solenoid jumps in but the voltage is not enough to keep it in.the solenoid then jumps out again ,the battery voltage rises causing the solenoid to jump in again and on it goes bang,bang,bang.

what can also happen is the battery will have enough in it to get the engine turning but this will drag the voltage down to low for the ignition circuit to work.no proper spark = no start.


peter.

[RealEstate]

Originally Posted by pdrvolvo

A low battery will give the "machine gun" effect i.e. as the key is turned the starter solenoid jumps in but the voltage is not enough to keep it in.the solenoid then jumps out again ,the battery voltage rises causing the solenoid to jump in again and on it goes bang,bang,bang.

Yes the battery was dead, 6 years old, and the noise was the solonoid. RAC came. Despite being fully charged overnight, the battery could only deliver 39A.

I bought a new battery from the RAC man, cost a few quid more than Halfords but being in wild Wales better things to do than look for a cheap battery. RAC fitted it checked charging current/voltage under load and also checked earths and current drains. All found to be in order. Good service by the RAC - always find them very good.

Modern batteries seem to die very quickly. OK one day - dead the next. Anyone know an easy way to tell if one's battery is about to give up?

Thanks all for the advice - which was spot on!