Another Faulty Alternator or ???

Joined: 09 Oct 2005 Location: Newcastle

Its been a while since I've been here so I feel a bit slack just coming back when I have a problem - but hopefully someone can help me out.

I left my lights in my 1989 suzuki sierra on the other day and ran the battery down - it didn't charge back up that well so I replaced it. The new one battery then had problems, so I checked the voltage reading when the lights were off and the car running - around 14.5 volts, but when the lights went on the voltage went down to about 12.3V.

Turns out the alternator belt was loose, so I tightened that and then checked the voltages again - it was now reading ~15.5 volts. I thought that was way too high so I looked in the manual which said that if its higher than about 14.5 volts, the regulator is gone. The regulator in the sierra is within the alternator, so today I went to the wreckers and picked up another one. I've just finished installing it and its reading 15.89 volts measured from the actual alternator.

Now I'm thinking that this alternator' regulator is probably stuffed as well - has anyone got any other suggestions? I 'spose it serves me right for trying to do things on the cheap and not take it to an auto electrician, but I do try to work on the car myself wherever possible.

Sorry about the long post, any help will be appreciated - although I probably won't be able to get back on here 'till later tonight 'cause I'm off to work... Hope it all makes sense.

Cheers

Nick.

Joined: 25 Oct 2003 Location: Melbourne Australia

It could be a second bad alternator (or rather reglator) but I am just wondering about the voltage sensing wire to the alternator and whether that could be screwing things up.

Joined: 09 Oct 2005 Location: Newcastle

chimpboy wrote:

It could be a second bad alternator (or rather reglator) but I am just wondering about the voltage sensing wire to the alternator and whether that could be screwing things up.

Thanks mate, any idea is good - any idea how I could check?

NIck.

Joined: 11 Dec 2007 Location: Perth

sierras have a fuesable link at the battery. over time they get corroded and or weak causing volt drop, might pay to check that aswell.

Joined: 11 Jan 2004 Location: Adelaide

nickw86au wrote:

chimpboy wrote:

It could be a second bad alternator (or rather reglator) but I am just wondering about the voltage sensing wire to the alternator and whether that could be screwing things up.

Thanks mate, any idea is good - any idea how I could check?

NIck.

Can you measure the voltage on that wire at the alternator? This tells you the voltage which the alternator is "seeing", and should be very close to battery voltage. If there's a big difference, I would guess there's a dodgy connection in that wire.

Joined: 09 Oct 2005 Location: Newcastle

The wiring diagram is here

The only wires going out are the ones to the dash light (marked L), the IG line (apparently needs 12V so that the alternator will actually charge assuming that its the same as described here:

http://www.genco1.com/tech_tip_details.cfm?id=106

and the other line is the output of the alternator, marked B. The voltage at B is up to 15.89V; I haven't actually measured any of the other ones, but the dash light is coming on with the key in the 'on' position, and goes out when the engine is started, so I think that the L and IG leads must be o.k.

Quote:

Can you measure the voltage on that wire at the alternator? This tells you the voltage which the alternator is "seeing", and should be very close to battery voltage. If there's a big difference, I would guess there's a dodgy connection in that wire.

Seems logical, but not sure which one I would need to check... If someone could let me know that'd be great.

I've decided to take the replacement alternator back to the wreckers in the morning (hoping its just a faulty one); its now out of the car. The bugger is that he changed over the pulley for me because he gave me a suzuki swift alternator which uses a different size pulley - and now I can't change the pulley back to the old alternator 'cause I don't have the correct tool - so I can't just drive around as is until I get the pulley changed back over or (hopefully) a replacement alternator. The wrecker seemed like not a bad bloke so I think he should be fine with it.

Another long post, I guess I'll let everyone know how I go in case anyone else ever has a similar problem.

Nick.

Joined: 09 Oct 2005 Location: Newcastle

scooby_74 wrote:

sierras have a fuesable link at the battery. over time they get corroded and or weak causing volt drop, might pay to check that aswell.

Would that cause the alternator to put out a higher voltage?

Thanks

Nick.

Joined: 11 Feb 2007 Location: Hobart

nickw86au wrote:

scooby_74 wrote:

sierras have a fuesable link at the battery. over time they get corroded and or weak causing volt drop, might pay to check that aswell.

Would that cause the alternator to put out a higher voltage?

Thanks

Nick.

if its sensing a lower voltage from the bat due to this link, then yes, it may well be pushing the voltage higher in an effort to charge a bat that it thinks is flatter than it is...

Joined: 28 Jan 2008 Location: Newcastle

Just a question how old is your multimeter,when the battery gets flat sometimes they read voltages higher than what it is.
Just a thought ,i have had this before ,had me scratching my head for a while..

Joined: 09 Oct 2005 Location: Newcastle

4runner_boy wrote:

Just a question how old is your multimeter,when the battery gets flat sometimes they read voltages higher than what it is.
Just a thought ,i have had this before ,had me scratching my head for a while..

Bingo. There was a little battery symbol but I thought that if the display is still working then it should be fine, apparently not. Don't I feel like an idiot. I tested the link from the battery to the alternator like scooby_74 suggested and there wasn't actually a problem. I then tested the multimeter on my partner's car again (I did it briefly earlier but not for long enough) and the voltage was slowly climbing like it did with the suzuki - it was like it was slowly building up to the ~15.9 volts. I went up to the servo late last night to get a 9V battery and now my partner's car reads at a constant 14.14V when running - I now need to put the alternator back in the suzuki to confirm, but I'm betting that it will now be fine too.

Thanks to everyone that helped - I guess that I've learnt not to ignore the battery symbol on the meter Rolling Eyes

- hopefully someone thats having problems will be able to learn from my mistake

Nick.

Joined: 25 Oct 2003 Location: Melbourne Australia

nickw86au wrote:

4runner_boy wrote:

Just a question how old is your multimeter,when the battery gets flat sometimes they read voltages higher than what it is.
Just a thought ,i have had this before ,had me scratching my head for a while..

Bingo. There was a little battery symbol but I thought that if the display is still working then it should be fine, apparently not. Don't I feel like an idiot. I tested the link from the battery to the alternator like scooby_74 suggested and there wasn't actually a problem. I then tested the multimeter on my partner's car again (I did it briefly earlier but not for long enough) and the voltage was slowly climbing like it did with the suzuki - it was like it was slowly building up to the ~15.9 volts. I went up to the servo late last night to get a 9V battery and now my partner's car reads at a constant 14.14V when running - I now need to put the alternator back in the suzuki to confirm, but I'm betting that it will now be fine too.

Thanks to everyone that helped - I guess that I've learnt not to ignore the battery symbol on the meter Rolling Eyes

- hopefully someone thats having problems will be able to learn from my mistake

Nick.

lol I've done that as well, so you're not the only one.

Joined: 09 Oct 2005 Location: Newcastle

The worst thing is when you don't realise until after you've spent money unnecessarily... but oh well, that happens...

Edit: I got a partial refund for the alternator which the wrecker didn't have to do... I got 40 out of the 70 bucks back which is pretty good.

Thanks again for the help guys

Nick.

Joined: 09 Oct 2005 Location: Newcastle

The original alternator is back in and output seems fine now that I changed the battery in the meter Rolling Eyes

.

Cheers

Nick.

Joined: 28 Jan 2008 Location: Newcastle

no worries mate im an auto elec and it had me stumped once

Joined: 09 Oct 2005 Location: Newcastle

That does make me feel a bit better... I was actually just ignoring the battery symbol thinking that if the display still worked then there was no problem. I guess I learnt for next time

Nick.