Battery ?

Got a phone call tonight at 10:30 from the missus - stuck on the forecourt of Sainsbury's garage with her Disco refusing to start. So off I went with a few basic tools and a torch. She had been working about three miles from the garage, and the car had been standing from about 4pm. It's very cold here tonight. Thick frost. Probably the coldest night so far. It had started fine when she came out of work. On the way home, the diesel light came on, so she went into the garage to get some. When she tried to restart, she said that it didn't sound very lively, and didn't want to catch. When I got there, the battery sounded pretty poorly. Rather than a nice "chugga-chugga-chugga - vroom", all I got was "Ga-wumm - pause - Ga-wumm - pause - ". I did the headlight test, and they dropped to almost nothing when cranking, so it seemed it was low battery rather than any issue with the starter motor or its connections. I'd got jump leads, but the garage guy wouldn't let us try to jump it in front of a pump, so we had to push it to the air bay. Ever tried pushing a Disco slightly uphill ...

Anyways, I jumped it from my car, and it turned over ok. Must say, it churned for a few seconds, but when it did fire, it caught and ran ok. Can a diesel 'flood' as a result of not turning over fast enough to start ? Is that why it was reluctant to fire initially when it was being jumped ? Once running, it drove back home ok, and felt normal.

So, what was going on here ? Tonight is the sort of weather when I would expect a battery to start dying if it was ready to, but surely, wouldn't it have been more likely to show a problem after it had been standing for six hours, rather than with the engine warm, and having run for a few miles already ? Or maybe, it gave its last gasp starting from cold, and three miles wasn't enough for the alternator to get enough back in there to overcome its failing capacity to hold charge ? I seem to recall when I had my old Fester a few years back, I had a similar thing happen. The battery hadn't shown the slightest signs of being weak or marginal in the weeks prior. It started fine one evening. I drove to the village chip shop, and when I came out, the battery just died. I remember someone saying - maybe even on here - that modern batteries often fail this way. So what's the concensus - are we looking at a bad battery ?

Arfa

Reply to
Arfa Daily
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Yes. :o(

Yes. Well, you get hydraulic locking, which can cause serious engine damage. You shouldn't crank diesels for long periods of time.

Almost certainly.

Reply to
Huge

It seems to be a popular hobby among Disco owners.

Reply to
Steve Firth

Sadly true.

And mine broke down in the gate, so I couldn't get a spare car round it.

:o(

Reply to
Huge

Ouch.

I'm currently looking forward to getting an exciting weekend fixing my tractor which someone[1] has broken.

[1] Naming no names, but she denies that she has broken it. It just doesn't work anymore. Like the Jeep that she didn't leave the lights on but when she got back to it the battery was mysteriously flat. And then she broke the radio by getting a jump start. With the booster leads the wrong way around.
Reply to
Steve Firth

No, the "Ouch" came when the TVR rolled off the trailer (which was on the back of the dead(*) Discovery) over my foot.

Ah. I've got one of those, too.

(* Sufficiently dead that the only thing working was the effing "Key in ignition" bonging.)

Reply to
Huge

In article , Dave Plowman (News) scribeth thus

I'd somehow doubt all the same that this would give erroneous readings. After all in order to supply the amps required that ciggy lighter would be well fed via thick "ish" wiring..

Reply to
tony sayer
[...]

That wiring wouldn't be connected directly to the battery terminals however...

Chris

Reply to
Chris Whelan
[...]

Yes, but when you strip it to make a connection, you can clearly see. The sizes used are pretty marginal on anything recent, and in some cases very undersized.

Chris

Reply to
Chris Whelan

I recently needed to take a feed from the main beam wiring near the headlight on a fusion. the wire was so extremely thin that I needed to use a red scotchlock on it or there was no contact.

Reply to
Mrcheerful

I'll bet they're not undersized or they'd get hot.

Reply to
Duncan Wood
[...]

Well, if they are carrying current then their temperature will increase!

Two fairly common faults:

Certain BMW rear light clusters burn out their earth connection. The earth wire is the same size as the individual wires, but carrying the total current. The connector is marginally sized, but the real problem is the small earth wire.

Similarly, Mk2 Focus headlights have wiring that is very marginal, and failure occurs at the terminations. The wire csa is smaller than older cars used for sidelights.

Chris

Reply to
Chris Whelan

Both of which fail due to crap terminations.

Reply to
Duncan Wood

A scotchlock? Thought only cowboys and alarm installers used them. ;-)

A single headlight only takes some 5 amps. So the wiring can be very thin. Even 0.5mm² is rated at 11 amps.

Reply to
Dave Plowman (News)

Hmm... well, just big enough and no more, then. Unlike previous, older generations, where ours were plenty big and no complaints from any quarter.

Reply to
Grimly Curmudgeon

Reply to
Ian Dalziel

You never had to replace a tail light bulb in a BX. Not only were the the wires thin they were made of fine brown rust with a pale green coating. Well that's what the last 2cm of wire connected to the IDC bulb holder was after a few years. So moving it to fit the bulb broke it and then it had to be stripped back and reconnected. If one got the joy of replacing a bulb for the 2nd time there wasn't enough slack and all the wires had to be extended by crimps as can't solder to copper plated steel.

LEDS will reduce the wiring needed. Each chain in an array will pull about 0.05A so maybe 0.35A. Normal 21W bulb 1.5A.

Reply to
Peter Hill

the feed only had to drive an LED so there was no point in taking anything more substantial and even complete failure would only result in a lack of main beam warning lamp.

Reply to
Mrcheerful

The very smallest cable normally found on a car is rated at 11 amps. Going smaller would make it too delicate.

It's things like heated windows that guzzle power and need heavy cables - and LEDs won't help that.

Reply to
Dave Plowman (News)

That's what it is rated to, to stop it overheating, softening the insulation, allowing easy displacement of insulation and exposure of the wire. (Ever seen an overheated wire burn as the wire "pops" out off the insulation?) It's not what it is rated to to give 13.8 volts at the load

- it's used some of those volts heating itself up. Volt drop = current x wire resistance, at 5amps 0.1ohm wire resistance is 0.5V drop. A bulb is rated in the expectation that it will get a decent voltage. Feed it 13v (96%, 0.8V drop) instead of 13.5v (0.3V drop) and it's output is reduced to 89% - effectively a 55W bulb is 49W.

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I've got halogen dim dip, the dip beams are put in series by a pair of relays. That says the halogen cycle doesn't work at low power and can reduce bulb life. I removed it from one car as the relays started chattering and the headlamps flashing - everyone got out the way! Should I give it the snip on the other car?

I remember the joy of 45W tungsten bulbs in 70's motorcycles. There was no halogen bulb with the same base so upgrade wasn't possible. Cibie made a mint from selling every UK biker with 12V electrics 60/55W H4 halogen headlamps.

Reply to
Peter Hill

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