Alternator issues - Any auto sparkys out there?

[brentw]

Okay i'm hoping someone can shed some light on what I'm missing before I possibly take it into the shop.

I have an amp gauge fitted and it has always showed 11-12volt on acc and then raising to 13.5-14volts once the car is going. I have recently replaced the alternator maybe 3 weeks ago as it was getting noisy and wasn't charging the battery properly. I also changed the battery as the other one had a bad cell. So now the gauge was showing 12.5volts at ACC and 13.5-8 with the car going.

I was coming home last night and it suddenly changed back to displaying 11.5volts and I appeared to losing voltage as I drove home. Ended up displaying 11.2volts by the time I got home. I turned the engine off and turned it onto ACC and it recovered to 11.6volts.

My Alternator belts are new and tight - no squeel. My car is still starting fine and I checked it with an multimeter and the battery was still holding 12volts even though my gauge displays 11.5volts. (Gauge is faulty perhaps?)

I've checked my 2x fusible links and they are fine. Checked the wiring off the alternator and it seems fine. Is there is easy way to check Alternator output so I can rule out a fault with that? (its in a prick of a spot) Just a thought my car should bring up an error if the alternator is not charging shouldn't it? I did upgrade to a 620CCA battery but it was recommended for a diesel pajero. I am leaning towards a faulty gauge unless my car becomes hard to start but just want to rule out anything obvious first. Sorry this is so long... just trying to cover everything.

PS: my headlights and interior is still bright so I don't think I'm running my battery down.

[Darwiniandude]

I can't diagnose without seeing of course, but keep this in mind:

I once bought a brand new alternator from a big retail chain. It stopped working after 24 hours or so.

I returned for a refund (they had it for weeks before they gave refund, to check I hadn't damaged it apparently) and instead of waiting got a used one from a wrecker. The used one lasted years.

So a new part can fail suddenly, it is possible.

Or it could be a wire dropped off it, or the battery light in the dash blown maybe. Many cars run the alternator through this globe, strangely. Not sure if these do. But a failed alternator light bulb can stop it working.

[XXXceed]

Do you have a multimeter ? If so, just put it across the battery terminals without car running, check voltage, should be mid to high 12 volts.start car and check voltage across battery, should be somewhere around 13.2 to no higher than 14.5 volts.
Hope that helps.

[brentw]

Thanks Guys, yeah i put a multimeter across the battery with the car running and it was only 12.5volts. I guess I could put the old one back in and see what readings I get. I bought it off an ebay seller but they had a good rep. I'll try the old one back and go from there I think.

[Kiteman]

There used to be an autoeleccy on. here called john McFarlane but I haven't seen him around for a while. From memory he'd been in the game a long time, I think I remember his signature saying.

Try to pm him. He was pretty good.

[hiedipro]

Thanks Guys, yeah i put a multimeter across the battery with the car running and it was only 12.5volts. I guess I could put the old one back in and see what readings I get. I bought it off an ebay seller but they had a good rep. I'll try the old one back and go from there I think.

I take it you are talking about putting the old Alt back. If you are capable pull it apart & check brushes. It may only be that is the problem because you didnt say it completely stopped charging.
If diodes & wiring OK then brushes & bearings are cheap. Must be someone close who can guide you.

[craka]

From memory for checking if an alternator is operating with vehicle switch off, remove the positive/charge lead from the alternator, start vehicle so alternator is spinning (be careful of belt, loose sleaves, fingers etc. Set multimeter to volts DC range one probe to the charge connection of alternator and one to vehicle ground (chassis etc). Should get a reading of somewhere around 14 Volts . If you get much less than that, that will be your problem.

[Kiteman]

Cracks,
Never run the alternator without battery supply. 9/10 times you'll damage it due to no load. Voltage goes thru the roof.

Don't offer advice if you don't know what yr talking about.

[my.paj]

The 2 tests I do before I go changing things is multimeter on the battery with car running then test output from alternator its the one wire that bolts on the back of alternator, this is only to test if the output is the same from alternator and battery as there may be a fault in the wire.

[craka]

Cracks,
Never run the alternator without battery supply. 9/10 times you'll damage it due to no load. Voltage goes thru the roof.

Don't offer advice if you don't know what yr talking about.

Um it's just an open circuit test/ ie no load as you said. No problems that I can see there, not sure why that would be a problem, but please explain rather than shoot me down. Are your stating the alternator is going to go in overrun ?

Yes his voltage is going to be higher than with out load that was the point, what voltage range are you referring to as per "the roof"?

[hiedipro]

Um it's just an open circuit test/ ie no load as you said. No problems that I can see there, not sure why that would be a problem, but please explain rather than shoot me down. Are your stating the alternator is going to go in overrun ?

Yes his voltage is going to be higher than with out load that was the point, what voltage range are you referring to as per "the roof"?

Kiteman is dead right. No battery, no reference voltage.
Same with a solar panel, no battery & you have 28+ volts, kill your radio etc.

[brentw]

Thanks for all the responses so far blokes

Just had a look online, I had no idea alternator bearings were so cheap. I have a bit of time off over Christmas from tomorrow so I am going to pull the old one apart for a look and change the bearings and bushes. I'll put it back in and that should tell me if I have a problem with the wiring or not.

[mike nm paj]

Hey mate change the altonator I had a v6 nl and went through 3 in 6 months turn the ignition on and make sure you. Have a altonator light showing if so start it up check charge rate should be over 13 volts min then bring revs up to about 2500 rpm and recheck it if all ok great. If you have no charge but you have a a altonator light go to the 2 pin plug on the altonator and if you have a test light check for power going in if you all looks ok then it the altonator if you need a hand to check it over pm me and ill be glad to help as im in at redwood park

MIKE

[hobbo]

I had an alternator charging problem like this but it turned out I forgot to tighten the earth wire!

[brentw]

Cheers Mike, you drink rum as I've got a crapload of it atm haha!! I'm pretty sure the earth wire is all good hobbo but I'll pull it the car apart over the wknd and have a look at it. I'm getting quite efficient at pulling the air intake/box and turbo/coolant hosing out.