Electric help...please!!

[TomG]

Hey everyone, i'm at my whits end, i really need any ideas...

My car hasn;t been chargin for a long time, so i replaced the dynamo with an alterator.

Still went flat.

Replaced with another fully charged battery.

Still went flat.

Replaced the wire from the alterator straight to the battery +ve, with a brand new, thick length of wire.

Still gone flat.

I'm pretty sure the alternator is workin, but my battery is only lastin about a week, and i'm startin to lose the will.

Anyone got any thoughts?

Ta

[Alf ista]

Difficult area, the ol' car lectrics. Anyway, my limited ideas: Are all your earths ok? Can you check that the alternator is putting out what it should? Sounds like it aint.
Hugh.

[TomG]

I can re-check the earths, i've had a bit of trouble with them in the past. I know i'm gettin an earth to the body, coz all the lights work off that, but maybe it's not enought for the battery.

As for the Alternator, i had it checked by a proper leccy sparky, had the multi meter on it and all, said it was fine, and then went flat 2 days later. He advised i redo the wire from the alternator to the bat, so i've done that, but apparently no no avail.

[Derek UK]

Do the volts, measured at the battery with a meter, increase form about 12.6 at tick over to about 13.5-13.8 when you give it some revs? If no meter do the headlights brighten up when increasing the revs from tickover? Put your heater fan on full while checking with the lights to load the battery more. If the alternator doesn't pass either of these tests, it needs checking over. If a S/H one it might need brushes. Check the earth lead from the bell housing to the body. It's just below the steering shaft.
Ron K will be along soon and I'm sure he'll have ideas.

[TomG]

I don;t have a multi-meter, but the light don't get any brighter under revs, i was kinda hopin that was due to them bein at full brightness, but it sounds like i might be very wrong. I know the earth you mean, it looks the same as the one comin off the battery, i'll check that tomorrow, hope it's that and not the alternator.

[AidanC]

What kind of alternator did you fit? Some have built in regulators & some don't - how did you wire it up?

[Moosejaw]

At the risk of stating the bleedin' obvious, when you say you replaced the battery with another fully charged one, do you know for a fact that the new battery is good?
I only ask because I've had a brand new battery die after 4 months.

Most of the kwikfit type places will have a proper battery tester. I'd make sure the battery was beyond doubt before I went any further.

[classicswede]

The other question is,

is it going flat as you dive or from being left over night?

[TomG]

AidenC: its a lucas ACR, off a metro or summiut similar.

Moosejaw: The battery was less than a few months old, and the other battery was only 5 months at the most, so i was hopin they were ok.

Classicswede: goin flat over the day, when left

[Alf ista]

I reckon its the alternator. Somethin aint right. Also, its a good idea to fit one of them battery disconnect devices. I have one of the ones that fits on the battery terminal, just screw it a couple of turns to disconnect all power. Its also a safety device and a security device too. It would stop your battery draining as it is sitting there.

[AidanC]

Yep - definitely worth ruling out a drain, especially as the problem is the same as with the dynamo. Also, you really need to get a multimeter - a cheap one for a tenner will do. Then check the readings at the battery to see if there's a charge when the engine's running. Checking the output at the alt won't do it. You'll definitely need a meter in the future anyway.

[AidanC]

Just wondering - how exactly did you wire the alt? Is it possible that its a good one but wired so that it doesn't detect a drop in volts - that its getting its own output back somehow so that the regulator doesn't pass a charge to the battery?

[Ron Kwas]

Guys;

Checking cleanliness and tightness of cables is OK I guess, and if I had electrical problems on a deserted island with no tools on hand, I would do it too, but if you're in the civilized world, you should take some measurements of the thesystem...without these measurements (system voltage, or charge/discharge current), it's all speculation and conjecture...and I wonder based on what was Tom advised to replace the alt to battery cable...perhasps some WAG (Wild Ass Guess)...and yes, batteries do fail on their own, so once fully charged (use mains charger), they can be disconnected overnight to seperate them from the vehicle system which MAY be draining them, but here again a measurement of discharge current drawn while nothing is powered ON should be done...valid information is what is needed from the patient, not conjecture!

Aidan; I don't wish to jump all over someone who is trying to help, but some your information and terminology is less than correct.
1. Regulator detects System Voltage and controls field current to enable output of (an alternator or gen equipped) charging system. Only on the oe generator equipped charging system, does the Reg "route" output current (through a cut-out relay contact), to the battery. On an Alt equipped charging system, output is directly connected to bat since diodes make cut-out relay unnecessary.
2. If the engine is running, there has to be a "charge"...more correctly stated, electrical system has power...but if this power is being supplied by battery or charging system is not known until, as you correctly point out, measurements are made. [The fact that lights don't get brighter when raising RPMs does suggest that charging system is not working...normally, (at elevated RPMs) it would pull system voltage up resulting in lights becoming brighter/whiter...this being an indication of system voltage.]

Cheers

[TomG]

Right, i've had the battery on charge all day, and its full again, also treated myself to a multi meter, so i'll go and have a play, and let you all know the results.

Cheers for all the advise peepholes, really appreciate it :D

[TomG]

Ok, just done a few checks...

Volts:
Ignition off - 12.8
Running idle - 12.8
Under revs - 12.8

Volts under stress (lights and fan on):
Ignition off - 12.28
Running idle - 12.30/12.31
Under revs - 12.30/12.31

Reststance ohms (battery -ve to body):
Engine off - 0.004
Running - 0.014
Under revs - 0.014

...any help to anyone?

P.s: this is on a fully charged battery

[TomG]

Reststance ohms (battery -ve to body earth strap):
ignition on - 0.045
Running - 0.024
Under revs - 0.018

[TomG]

Also, my amp lights not comin on, is that weird?

[TomG]

Right, i just had an idea, i took the other 2 wires off the back of the alternator, so there was just the new wire i out on the other day, direct to the battery, and the voltage went from 12.68 idling to 12.72 under revs and climbing, i know it's not goin up as much as it should, but least it's goin up right

[Alf ista]

Keep at it Tom! Your gettin there! :thumbs_up:

[TomG]

scratch that last break through, it does the same thing with no bloody wires attached, i think i may have a demon

[lizardking]

Dude from your figures I would say it's not charging I would be expecting 13.8v to 14.2v at around 1500 revs,unfortunately I would suspect the alternator from those readings,
ps. I've not forgotten about your trumpet I've just been very busy will sort it asap
Regards
Alex

[TomG]

Ha, cheers Alex, and i think you're right, i did the acid test, engine running, disconnected the battery, and the engine cut out... alternator not workin right.

Never mind, it was free, so i ain;t lost out, just get it sorted or get another one, job done :D

[AidanC]

Another step forward - won't take much more to sort it...