battery warning light

[dandaz]

hi

the light goes out when starting then comes on straight away...

I have 12v from the blue wire [alternator end] when van is running...

I did notice when I took the red wires off the spark was not very good....

I have had a engine fire and the cylinder thing is fried ,but it worked before...

the brushes seem fine...

any ideas?

[MidLifeCrisis]

Are you only seeing 12v at the alternator?
Because if the engine is running you should be seeing more than that from the alternator.
(It's possible that what you are seeing is 12v from the battery)

[itchyfeet]

I have had a engine fire and the cylinder thing is fried

What's that then?

As said alternator should give 13 to 14 or sometimes more 12v will be the battery voltage which is almost flat
A charged battery is more like 12.7 v

Changing the regulator and brush pack is probably the next step after checking the cable from the starter (iirc you have a dg)

[RedGus]

1. I have 12v from the blue wire [alternator end] when van is running...

2. I did notice when I took the red wires off the spark was not very good....

3. I have had a engine fire and the cylinder thing is fried ,but it worked before...

1. You should see 0V relative to earth when the engine is off, and battery voltage to the other side of the warning lamp (that's how the lamp lights when there is no charge from the alternator). Once the engine is running, you should see about 13.6 - 14.4V, depending on your regulator and quality of the wiring and connectors, to both sides of the warning lamp (that's why it goes out when the alternator is charging).

2. The red wires to the back of the alternator are permanently live, because they are cabled directly to the live post of the battery, via the starter solenoid. I can think of a few good reasons not to deliberately make a spark in the engine bay, so you would usually disconnect the earth strap to the battery before pulling off the red leads from the alternator. All that the "spark" tells you is that the cable was connected to the battery, then you disconnected it with a current passing through it. If you disconnect the red output leads while the alternator is running, you will probably do serious damage to the alternator.

3. What is this "cylinder thing"?

James

[RedGus]

Ah... I see Itchyfeet can type faster than me.

[AdrianC]

I'm going to guess the "cylinder thing" is just a small radio interference suppression capacitor.

Post-engine fire, I'd be checking the loom very carefully, but it does sound as if the alternator's goosed.

[dandaz]

trouble is mt tester only goes 12v ,am I right the yellow wire goes on the bottom spade?

the fire was 12 months ago and I only had problems with the alternator when I have been messing with the carb ,thinking about it I could have hit the wires getting the throttle on...

I stripped the alternator ,hence the red wires earthing.......too lazy to disconnect the battery...

[itchyfeet]

.......too lazy to disconnect the battery...

How did your engine fire start

[AdrianC]

trouble is mt tester only goes 12v

Buy a decent multimeter. Without one, you're wasting your time trying to do any electrical troubleshooting.

http://www.amazon.co.uk/dp/B0001K9XKW" onclick="window.open(this.href);return false; or similar.

[kevtherev]

Alternator repair shop, my guess is you blew the diode.

[RedGus]

^^^ Agree with what Kev says. If you pulled the spades off the output terminals with the alternator running, you've probably destroyed the rectifier diodes.

I'll add another vote for getting yourself a multimeter. There is so much you can diagnose with one, and lots of jobs that are just guesswork without one (as you've found).

James

[dandaz]

trouble is mt tester only goes 12v

Buy a decent multimeter. Without one, you're wasting your time trying to do any electrical troubleshooting.

http://www.amazon.co.uk/dp/B0001K9XKW" onclick="window.open(this.href);return false; or similar.

cheers ordered...

thanks all...

[dandaz]

trouble is mt tester only goes 12v

Buy a decent multimeter. Without one, you're wasting your time trying to do any electrical troubleshooting.

http://www.amazon.co.uk/dp/B0001K9XKW" onclick="window.open(this.href);return false; or similar.

bought one and battery is getting 11 v when running and 12 v when not ,tried it on the landy and 14.7 when running and 12.7 when not...

bought the Draper 60792 Digital Multimeter ,but had to use every setting before I got the right one is there anything I can test on the alternator?

[AdrianC]

trouble is mt tester only goes 12v

Buy a decent multimeter. Without one, you're wasting your time trying to do any electrical troubleshooting.

http://www.amazon.co.uk/dp/B0001K9XKW" onclick="window.open(this.href);return false; or similar.

bought one and battery is getting 11 v when running and 12 v when not ,tried it on the landy and 14.7 when running and 12.7 when not...

So it's not charging. Definitely.

bought the Draper 60792 Digital Multimeter ,but had to use every setting before I got the right one

V~ is AC (household). The other V is DC. I'm guessing you ended up with it on the DC 20v range...?

is there anything I can test on the alternator?

Take the small connector off, and make sure you've got +12v there with ignition on, engine not running. Other than that, at best you'll need some new brushes in it. But, given the earlier comments, it sounds like it's new alternator time.