Ive got a few symptoms, and a few possible roots, but i was hoping you clever lot may be able to narrow it down for me.

Ive been away for 10 days, and I came to my car this morn, and it was dead.
as in:

all dash info lights came on, and went out as normal, but upon turning over once the coil had gone out, it could barely manage 1 rev per second (though it DID turn over)

Jumped it off a passing car, and it runs fine. Airbag fault has come up but i think the airbag ECU may need rebooting, and this may be seperate issue caused by the jolt of jumping it.

in car clock came on at 00:00 00/00/1900

The car has ALWAYS been hard to start in winter, as in it doesnt seem to have the torque in the battery/started to get it up to compression speed when its cold (its a Diesel).
(It turns over fine with no sign of running out of power for as long as you like, it just cant quite hit compression speed.)
but ive never had the battery changed, and it always survives the winter (3 years now) and goes back to being fine in the summer.

SO potential problems i have identified, some of which you may be able to eliminate?

1) Battery is weak? low on top volt grunt, so suffers under sticky fuel situations in the cold, and without being charged daily.
2) Alternator is bust/tired/belt is slipping, so battery isnt fully charging?
3) I put a new head unit in last year, and i dont THINK the car has been standing for more than a weekend since. To get the unit to work, i had to fiddle some wiring (just on the stereo loom), it is possible the unit drains the battery? but out of a big diesel battery over only a week? less likely i think?

thanks team!
x

It’s unlikely to be an alternator fault, they either work or they don’t.
You’d hear the belt slipping if that was the problem.
Check the alternator output to be sure if you like, should be around 13.8 to 14.2 volts.

Disconnect one battery lead and put an ammeter in series between the battery and the lead. I don’t know what the standard current draw would be, but I would imagine it’s a fraction of an amp to run the alarm and stereo on standby.

Sounds like you just need a larger capacity battery though.
If you’ve got a trade card, Halfords are pretty reasonable for battery prices, or they were last time I bought one.

Sounds like the battery has just about had it. How old? OEM’s will last between 5 and 7 years, replacements 3 to 5.

Had a similar thing with my Mondeo last winter and my wifes Astra last week. Interestingly for the Astrat an OEM from Vauxhall was the cheapest and a heavier duty unit than Halfords/Motorfactor/On line……….

Batterys have only got a life of 2to4 years usually.Also sounds as if the plugs need doing if it is hard to start in the winter.

New battery. They are consumables you know.

And if you are worried about the head unit, get a multimeter on the battery.

as above slippoing belt squeals. Broken alternator would mean car not starting ever. Bascially battery wont hold a charge so replace. As above check nothing draws a current when ignition is off.

Battery would be my guess.

That said, I had similar issues on an old Escort I had; sometimes it’d be fine, sometimes I’d come to it and -click- dead.

Long story short, a series of mechanics and auto-electricians failed to fix it; went directly to Lucas in the end, who diagnosed and fixed it in about 30 seconds. Turned out to be a faulty rectifier on the alternator which would periodically empty the battery for fun.

Put a new battery on, is it worth all this hassle for the sake of 50/60 quid?

If your close to suffolk area I’m more than happy to sort out a trade price on one for you (no i do not work for any motor factor places)

Each heater plug takes *about* 20 amps if working correctly therefore 80 amps of current needed for 10-15 seconds ish to work heater plugs, possible more depending on ambient and coolant temperature. If a bttery is on its was out it will kill it stone dead fairly quickly giving the symptoms you describe.

As molgrips says batterys are serviceable items and because they are still of the lead/acid type they get sulphation which eventually causes failure of one or more cells and a car that struggles to turn over.

new battery going in tommorow i guess. not worth the hastle.
it probably needs doing.
cheers Ken

There is something FAR wrong with the battery in my diesel Passat then…lots of short journeys and still going strong after 9 1/2 years.
Serve me right if it dies tomorrow. LOL!

New battery time, mine died after a longish drive home, get a quality replacement.

probably battery,but one thing I’ve come across in the last 20 yrs of fixing diesels that gives a slow starting speed is a blocked fuel filter.
not common,but I’ve had two in the last year with this problem.
one other possibility is a bad earth to the engine,or a bad/dry joint in the starter motor or solenoid circuit.

Halfords and others have a battery tester and they’ll check it for free. It sounds to me like the battery but getting it tested might just save you a few quid…