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| How to test an alternator? https://auszookers.com/forum/viewtopic.php?f=5&t=45879 |
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| Author: | Heideisadog [ Tue Apr 15, 2014 12:58 pm ] |
| Post subject: | How to test an alternator? |
Heyhey. I went out for a drive in the zook the other day and the radio went off, light went dim and the horn hardly worked. Now the car won't start but I can hear it clicking when I turn the key. Today I have brought the battery into work and charging that up and I'll put it back in tonight though I am wondering if my alternator may be stuffed and not charging the battery and running the electronics correctly. How do I go about testing the alternator? Someone at work suggested I get the car running and hold a screwdriver close to it and if it's working it should create a magnetic pull that'll attract the screwdriver towards it. Is that correct? And what other things should I test? Maybe it's not the alternator? Anyone have any ideas on what it could be and the solutions to this problem? Thanks!! Thomas. |
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| Author: | droverdave [ Tue Apr 15, 2014 12:59 pm ] |
| Post subject: | Re: How to test an alternator? |
With the car running use a multimeter to test the battery, should be between 13 and 14V if the alternator is working. With the car off it will be around 12V. |
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| Author: | Heideisadog [ Tue Apr 15, 2014 1:19 pm ] |
| Post subject: | Re: How to test an alternator? |
Alright thanks I'll see if I can get one. And basically if it's not 13 or 14v I'll need a new alternator? |
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| Author: | droverdave [ Tue Apr 15, 2014 1:24 pm ] |
| Post subject: | Re: How to test an alternator? |
Well it just means the alternator isnt charging. Which is either a faulty alternator or wiring i guess. |
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| Author: | murcod [ Tue Apr 15, 2014 2:04 pm ] |
| Post subject: | Re: How to test an alternator? |
Keep in mind if the battery isn't healthy then it could be dragging the alternator output voltage down - especially at idle. PS: Most battery places will check out your battery for free, it might be worthwhile doing before looking further. |
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| Author: | Heideisadog [ Tue Apr 15, 2014 3:31 pm ] |
| Post subject: | Re: How to test an alternator? |
Ah right... I tested my battery at work today but it was too flat for the battery inspection tool so I will check it again soon now it's been charging for a few hours |
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| Author: | 31zook [ Tue Apr 15, 2014 5:53 pm ] |
| Post subject: | Re: How to test an alternator? |
Should be 14.4 at the stud on the back of the altenator. If its different betweem the back of the alt and at the batt check the wiring/load test the battery. Sometimes the belt can silently slip and act lile its loosing voltage. So check your belt is tight, give it a rev to check the regulator is functioning, load it up with radio/AC/highbeam and then check your output. My money is on the alt being stuffed, and the battery covering up for it. |
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| Author: | Heideisadog [ Tue Apr 15, 2014 7:40 pm ] |
| Post subject: | Re: How to test an alternator? |
So I got a multimeter and started the car and tested the battery and it came up with 14.7. I didn't test it from the stud... What should I do to test that? Ground and positive on the stud? When I tested the battery at work after charging it came back perfect. All in good working order, was just out of charge. I'll test it again in half an hour again with lights and radio and all that on! But now I'm a bit confused... |
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| Author: | Mike57 [ Tue Apr 15, 2014 7:53 pm ] |
| Post subject: | Re: How to test an alternator? |
I had an issue recently with my daughters VW where the voltage was right but the battery was not charging. Turned out to be a melted connector that was corroded and that caused the heat. While there was enough contact for the voltage to look right there was insufficient current flow. Was misdiagnosed twice by the RACV. Anyway it is good to also use a clamp on current meter or check that all the connections are clean and no sign of overheating. Just a thought. |
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| Author: | Heideisadog [ Tue Apr 15, 2014 8:16 pm ] |
| Post subject: | Re: How to test an alternator? |
I'll double check the connections but it's a pretty new battery and the terminals are fresh. I'll check out some of the plugs now too! |
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| Author: | 31zook [ Tue Apr 15, 2014 8:17 pm ] |
| Post subject: | Re: How to test an alternator? |
I've had regulators play up, test correctly for a bit then dieing again in 30mins... Get a cigarette lighter plug and cut it, join the positive and negative to the multimeter and go for a drive, easiest way to get a real time display. 14.7 is a bit high... |
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| Author: | Heideisadog [ Tue Apr 15, 2014 8:39 pm ] |
| Post subject: | Re: How to test an alternator? |
So I just did some quick testing with the multi meter and this is my results: All car lights, spot lights and radio on: 12.3 ground and alternator 12.4 positive - negative on battery All car lights and spot lights, no radio: 12.7 " 12.5 " Just car lights, no spot lights, no radio: 12.9 " 12.8 " All lights off, spot lights off, radio off: 13.2 13.1 Car off battery connected into car: 13 |
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| Author: | Mike57 [ Tue Apr 15, 2014 9:11 pm ] |
| Post subject: | Re: How to test an alternator? |
This would indicate to me that the alternator is not charging the battery. You should have over 13 volts in all those situations. The drop in voltage as the current draw increases says to me that the alternator is not doing much at all. To be sure you need to increase the revs a little and not just do it at idle but it is not looking good. If you checked all the connections then I would get an auto electrician to check it out if you want to be certain or just get a recon alternator. |
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| Author: | Heideisadog [ Tue Apr 15, 2014 9:20 pm ] |
| Post subject: | Re: How to test an alternator? |
I did all the testing at about 2000 revs not just at idle. I'll start looking into alternators. What should I be looking for to put into a 96 leaf sprung sierra? Could my battery be too large? Or something like that? I'll get my battery specs tomorrow during the day. |
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| Author: | Blakey [ Wed Apr 16, 2014 7:57 am ] |
| Post subject: | Re: How to test an alternator? |
Heideisadog wrote: I did all the testing at about 2000 revs not just at idle. I'll start looking into alternators. What should I be looking for to put into a 96 leaf sprung sierra? Could my battery be too large? Or something like that? I'll get my battery specs tomorrow during the day. you can't really have a too large a battery for an alt, the alt will only output what it can regardless what battery is connected to it id check your sense wire as well if its not there at all or very high resistance your Volt regulators will probably not turn on. do you have a dash light for your alternator not charging. usually a battery symbol. |
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| Author: | droverdave [ Wed Apr 16, 2014 9:29 am ] |
| Post subject: | Re: How to test an alternator? |
I would just take your alternator to get rebuilt rather than buying a second hand one. It costs a bit more, but you know its brand new. Last time i did one it was about $100-150? an auto electrician can also bench test your alterntor and check to see if its stuffed. |
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| Author: | Heideisadog [ Wed Apr 16, 2014 12:54 pm ] |
| Post subject: | Re: How to test an alternator? |
Okay wasn't sure just a thought. What's the sense wire sorry? And how do I check that! And no, none of the dash lights are on. Oh yeah? That isn't too bad! I'll have a look into that. Thankyou! |
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| Author: | Blakey [ Wed Apr 16, 2014 1:31 pm ] |
| Post subject: | Re: How to test an alternator? |
the sense and dash light connect to your alternator, via the plug should be 2 small cables. if you pull it off check watt voltage you get on them one should be 0 and one should be what your battery has as its the sense and it tell the alt what voltage is at the battery and either throttles back the volts or increases it. if it gets back a really low voltage it thinks its not sending out 13.5-14v so it increases what it output if it get nothing back it could turn the regulators off completely for safety of its self. |
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| Author: | 11_evl [ Wed Apr 16, 2014 1:41 pm ] |
| Post subject: | Re: How to test an alternator? |
Sounds like your taking more than the alt can give. Stop mucking around with the Suzuki alt and do the ford alt swap. Search should be plenty write ups. You will Neva have another issue with any amount of lights |
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| Author: | 11_evl [ Wed Apr 16, 2014 1:43 pm ] |
| Post subject: | Re: How to test an alternator? |
Std Suzuki alts are 45-55 amp? The ford alt will be either 100 or 110 amp. Will not hurt your battery |
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| Author: | Heideisadog [ Wed Apr 16, 2014 1:48 pm ] |
| Post subject: | Re: How to test an alternator? |
Oh really? That could probably be right... Few light, decent sound system with amp, UHF . Alright I'll do a search on that tonight. Sounds like a good option. Is it a hard thing to do? |
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| Author: | droverdave [ Wed Apr 16, 2014 1:54 pm ] |
| Post subject: | Re: How to test an alternator? |
Add up the current draw of things in your car and how often they are on, i highly doubt you are over drawing on the alternator. |
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| Author: | Heideisadog [ Wed Apr 16, 2014 2:43 pm ] |
| Post subject: | Re: How to test an alternator? |
You don't think? I'll be adding some more lights and a winch soon and if like to do a dual battery system, would that make it more reasanable for the larger alternator? Or still recommend just rebuild my current alt? |
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| Author: | droverdave [ Wed Apr 16, 2014 2:54 pm ] |
| Post subject: | Re: How to test an alternator? |
Well upgrading is probably a good option, but make sure that your old alternator is actually the issue before you go upgrading. Or you might spend time and dollars and be in no better position. |
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| Author: | Heideisadog [ Wed Apr 16, 2014 4:52 pm ] |
| Post subject: | Re: How to test an alternator? |
Yeah great! I'll make sure that's the problem before I start doing any radical and expensive things. I'm going to double check and change some connections this weekend. If it doesn't sort things out I'll replace/ upgrade the alt. Thanks for your help guys! |
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| Author: | Blakey [ Thu Apr 17, 2014 6:45 pm ] |
| Post subject: | Re: How to test an alternator? |
11_evl wrote: Sounds like your taking more than the alt can give. Stop mucking around with the Suzuki alt and do the ford alt swap. Search should be plenty write ups. You will Neva have another issue with any amount of lights while you can take more then the alt can give it will be drawn from your battery. think of an alternator as a constant voltage source with a limited amount of amps. check your dash lamp. in old alternators if the lamp blows so does the excitation current and it will produce no power. this comes back down to the sense and lamp wire on the back of the alt. |
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| Author: | 11_evl [ Fri Apr 18, 2014 6:18 am ] |
| Post subject: | Re: How to test an alternator? |
Heideisadog wrote: So I just did some quick testing with the multi meter and this is my results: All car lights, spot lights and radio on: 12.3 ground and alternator 12.4 positive - negative on battery All car lights and spot lights, no radio: 12.7 " 12.5 " Just car lights, no spot lights, no radio: 12.9 " 12.8 " All lights off, spot lights off, radio off: 13.2 13.1 Car off battery connected into car: 13 And this info is not enough for everyone to realize it's the alt No load it charges great, start turning stuff on it drops voltage. Spotties and other accessories really make std setups struggle. Night runs I used to always need to carry jumper cables. Regardless you may or may not need to get bigger ford alt but why not. It's a very straight forward job and will be great for any upgrade. I run a small battery in my car with no dramas. But hey what would I know |
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| Author: | Gwagensteve [ Fri Apr 18, 2014 7:21 pm ] |
| Post subject: | Re: How to test an alternator? |
Apparently it's cool to hate on the EL/EF alternator swap though. Must be because it's cheap, easy and effective. Let's do some rough addition. 2x 100w driving lights= 16A Headlights, tail lights= 12A Ignition, dash lights, radio etc= 10A? That's a conservative 38A. EFI cars show closer to 15A just running the car with no lights. Even though the stock alternator is rated at 50A, once hot and on a test bench it's not unusual to see them peak at around 35A. That's at around 3K too, not idle, or 2k rpm. My falcon alternator will deliver 45A measured, not theoretical, at idle. Steve. |
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| Author: | 11_evl [ Fri Apr 18, 2014 8:00 pm ] |
| Post subject: | Re: How to test an alternator? |
Nissan n15 is a good swap if a ford alt is not cool. Not as many amps but much better suzuki |
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| Author: | cairns27 [ Fri Apr 18, 2014 9:32 pm ] |
| Post subject: | Re: How to test an alternator? |
I brought a standard alt a year ago from Ashdowngraham, they're 60 amps now. bye |
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