battery / alternator problem

The battery on my 1.3 driver recently keeps going flat and i could do with some advice. I replaced the battery and the new one went flat. So i replaced the alternator but tonight while driving along the electrics slowly seemed to fade like before (dash light dimmed, wipers moved very slowly) and then it wouldnt restart after being parked.

Is there anything else which could be flattening my battery?
Is there a way of testing the alternator to see if the new one is working properly? I've read some posts about using a multimeter on the wires coming out the alternator and checking voltage is above 13V but I'm not sure how to do this as the wires coming out the multiplug all look sealed up to me.

Any other advice gratefully received. Thanks

do you have an alternator warning light on the dash? (batter pic lights up red) as if the bulbs blown then the alternator will not charge as the ciruit is incomplete.

simon

funny you should mention that. The dash warning lights and some of the dials (rev counter, fuel and temp guage) recently stopped working. I put it down to bad connection behind the dash as they used to start up again with a thump on top of the dash. Do you think this has broken the circuit somehow?

I'll try taking the dash apart later on and see if i can see why the lights arent working. Searching the forum it looks as though the multiplug and/or a bad earth may be to blame. Does this sound about right?

took the dash apart yesterday and couldnt find anything obvious like loose or burnt wires or any damge to the circuit on the back of the clocks. Wasnt able to try putting in a new earth as i wasnt sure which of the dozen wires it was. Anyone have any ideas?

Is there a fuse controlling this part of the dash? rev counter, fuel/temp guage and lights in the centre like indicators. The power is definately getting there as the clock is still running which im guessing rules out a blown fuse.

Finally is it likely that the battery continuously going flat is related to the dash  problems or am i barking up the wrong tree?

The only real exact way to test an alternator is to hook up an ammeter. However, you can interpret voltmeter readings to give a pretty good test. Hook the voltmeter up at any +12V point, which is constantly live (even the battery terminal if you want. Before starting the engine, you'll get a reading from the battery, this should be around 12V-13.5V. Start the car but try not to let it rev, ie apply very little/no throttle so the alternator doesn't start charging. During starting the voltage will drop to maybe 9V, but then it should gradually come back to around 11-12V. Then rev the car to 2000rpm or so, this should speed up the alternator enough to make it charge, the voltage should go up to 13-14V then gradually down to around 12.5-13.5V over time.

Thanks for your reply. I finally got some time to have a go at this today. Apologies for long post.

Testing voltage across the battery terminals i got 12.2-12.4v at both idle and while revving engine by pulling choke out. So it doesnt look like its charging.

I opened the back of the plastic plug on the alternator to expose the back of the spade connectors. With the negative multimeter lead on an earth strap on gearbox side of engine and the positive lead on either of the bottom two larger connectors with red leads i got 12.2v while revving engine, same as at battery.

Presumably at least one of these is connected to the battery to carry the charge so, assuming the alternator is working, the voltage should go up when revving like you said in your last post, even if theres a problem elsewhere. However i'm not too good with electrics so could be barking up the wrong tree.

Does this mean the alternators a dudd or should i look elsewhere for the source of the problem?

Im still not sure if the battery light on the dash is working as the dash problem still isnt sorted, see other post. However im guessing that the top connector in the plastic alternator plug is the one goign to the dash mulitplug position 12 (labelled ladek) as they're both blue wires and look pretty similar. There's continuity (tested using ohms setting on multim) between this blue connector in mulitplug and the multiplug earth cable (brown one, no.2) so im assuming the bulbs ok as otherwise it wouldnt read at all.

Don't know about there, but over in the states you can take an alt. to  a parts store to have it tested.

Is your blue signal wire getting power when the key is on? And you're sure you have a good ground, i think. Then if you have two red wires on your alt. jump them both the the positive on the battery. If you have one then run just that one to the positive (you ahve a single wire alt in that case)

If it's a wiring/harness/fuselink/etc problem, it'll charge. If it's an alt/rectifier/brushes problem, you'll have the same issues after jumping. Just had the same on my 1.7 Wabbit L, turned out one of my red wires was broken somewhere in the harness. made a new one jumping both to the battery until i can make it pretty when it's warmer out. Been working great for a week.

Also, seems to be a lot of this going around. Hrmm. Posted this shortcut on 1203812390 forums today.

Thanks i'll pick some wire and give it a go. Is there any particular sort of wire should i use as i dont want anything melting on me? Last time i was out i noticed there wasnt an earth cable connected directly to the alternator like other cars i've had. Am i missing one or does it earth some where else on the circuit? Cheers

Most of the setups I've seen there was an earth/ground right from the alternator casing somewhere to the block or chassis. I have mine to the block. If you think that's your problem, try grounding it to see if it works.

I used 8 or 10 guage wire, don't remember which. Working perfectly for me!

Problem seems to be sorted now without me doing anything.

I was all set with new wire in hand when my non-driving housemate who i'd roped in to helping me revved the hell out of the engine when i asked her to give it a tap and the alternator suddenly started charging and it now reads approx 13.5v when the engines running.

I'm certain it wasnt working before as i'd been driving around normally flattening batteries for a week and a half. Perhaps the gentle persuation my housemate gave it loosened the new alternator up? I dont know what's happened, but fingers crossed it stays this way.

Cheers for your help guys. I'll post up all the readings i get off each of the red and blue connectors when the alternators charging and not in case its of use to anyone in future. It'll have to be tomorrow though as its now too dark for me to read the multimeter and my housemate has long since got fed up of sitting in the car turning keys and revving the engine when i say so.

Good news!! Still worrisome! I hate problems that go away, i'm always afraid it will just show back up again.

Hope that it stays working for you!

looks like i spoke too soon. Checked it properly last night and it gets 13.8/13.9 at idle with just engine running but as soon as i turn the lights on it drops to 12.4/12.5.

If i switch stereo, heater and heated rear window etc on it drops to 11.7/11.8v. Is it safe to assume the 'new' cheapo ebay alternator isnt working properly? The voltage does increase if i tap the accelerator and the lights get brighter but they never used to before all this trouble started.

All the spade connectors, battery connectors and earth straps were meticulously scrubbed and rubbed down with a little wet and dry so should be fine.

Hard to say. with heater, brights, turn signal, and radiator fan on i'm getting right at 12. The key is to watch if it's charging. When you turn something with a heavy load on (like the radiator fan) the needle should drop then come back up a little. That should tell you that the alternator is kicking in to compensate for the load. It's strange that tapping on it made a difference. If you have good ground that just sounds crazy. As for being a little brighter when you rev it, i get that a bit if i'm idling. Lights are very very slightly dimmer while idling, but once i pass 1100 rpm are bright and constant.

You may have a regulator/rectifier problem. Perhaps it's not holding back at higher rpms. If that was the case though your voltage should soar through the roof when you're at the higher speeds. I had an S-10 once that had that problem, always putting out a constant high 20's almost 30 volts. Had to switch the alty as the regulator was internal.

Thought i'd update this. I took the car to an alternator place round the corner and within 5 mintues the guy said he reckoned the faulty dash was causing a bad earth and reccomended taking the blue wire off the alternator.

Since doing that the voltage jumped up to around 13.3v with all my stereo, heater, heated rear window etc switched on. The car has run fine without the wire on and ive never seen my windscreen wipers move so fast!

Best of all it didnt cost me a penny, other than the bottle of wine i bought him for helping me out. So if anyone in coventry needs starter motors or alternators head to SAC at Spon End.

Wow! So the wire going to the gauge inside the dash was shorting out or something? Maybe something wrong with the gauge? Weird, first time i've ever heard of that! Congrats on solving the problem!