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Battery? Alternator? How to test with Multimeter?

Discussion in 'Technical and Troubleshooting Torque' started by cam77, May 13, 2006.

  1. Howdy. I will ask a question then give you background info.

    If I buy a multimeter, how do I check to see if my battery is alright or not, and whether the alternator is providing sufficient charge?

    The background - had a small problem with the Spada this morning. Drove to Granville to do my P's. Anyway, stopped at the servo beforehand, then when I tried the ignition, it felt like a flat battery. Engine didn't kick over much, oil and neutral light were much dimmer than normal.

    So anyway I push started it, which was fine :cool: , and prayed to the Spada Gremlin Gods not to do this to me on the morning of my P's test :mad:

    Anyway, first chance to start the bike during the course, no starter motor activity AT ALL. None.

    Same thing again, push started it, continued with the course, and left it idling between a few sections. Didn't have another problem for the whole day, which included turning it off again another 5 or so times, after which the bike started immediately like there was nothing wrong... :?

    So the situation is this: I have had the bike for 3 months, so I don't know how old the battery is. I think the alternator is working alright - the headlight gets significantly brighter each time I rev the bike.

    Any thoughts?
    :cool: Cam.
  2. With the engine running check the voltage at the battery - if it's stable and around 14v then the alternator/voltage regulator are working fine. If that checks out then test the voltage at the battery with the engine off - that should be around 12v otherwise the battery is either not fully charged or unable to be fully charged (ie stuffed). It does seem most likely that the battery is the problem - but don't neglect to check the connection between the battery and the leads. If this gets dirty/corroded it can prevent the battery from charging fully.
  3. Check temperature of the regulator. If it's burning the skin off your fingers,
    then something is definately wrong (ie stuffed reg).
  4. Being a Honda I would lay money on the problem being the regulator/rectifier. Honda seems to have the dodgiest electrics this side of a Lucas equiped Triumph. I have 2 of them (Hondas) so I feel I am qualified to comment :LOL: You will find it will an intermittent problem at first. You are just lucky it hasn't taken out the battery as well. When you mount the new reg/rec only use 1 of the bolts -this will allow it to expand contract without cracking the pcb inside. Make sure it has a good earth. To test your alternator find the wire coming out of the engine casing that heads to the alternator. Unplug it & find the 3 same coloured wires (usually yellow on a Honda) Hook a 12 volt headlight globe across each of the yellow wires in turn. Should glow bright as on each wire (with motor running of course)
  5. Going by the symptoms that he's described I'd say that the charging system is fine. I'm tipping a wallaby ted (roo ted's brother) battery.

    To the OP, rip the battery out (this gives you an excuse to have a look around your bike's innards, as it were). Check the water level. If the battery's dry then it won't hold a charge. Top up with distilled water (even normal water is probably OK as a temporary fix). If the water levels are OK, then the battery may have reached the end of its servicable life.

    Get it started. Now, with a multimeter, place the leads over the terminals. The battery voltage should read around 14v give or take one or two either way. As you rev the engine, it should move up and down.

    If it is a problem with the alternator or reg/rectifier as indicated by a steady voltage output then it's probably time to spend some dough and get it looked at professionally.

    But first, do the easy checks - battery, cables clean and tight, etc.

    Good luck.

    And let us know what you find.
  6. I beg to differ. Had the same symptoms myself. All of a suuden it took out the battery -overcharged it. Rec/reg tested fine. Dropped in a new battery. Went fine for a few weeks. Then took out another battery. Rec/reg still tested fine. Replaced rec/reg (on advice from a motorcycle electrical specialist) & all has been well since -a year and a 1/2 now. Common Honda fault. If you really want to isolate the battery as the problem just get a load test done on it.
  7. Yeah, but first at least check the water level in the battery. It's the easiest thing to do. And it eliminates one potential problem source.

    Anyway, what sort of Honda is this fault common to? It's never happened to any of the Hondas that I've owned.
  8. ok as others have said, seeing as the bke is running fine when going. Thats a good indication that the charging system is ok ( for now )
    So i'd be checking

    A: your battery Terminals ( clean and making good contact )
    B: check the H2O levels i you can, you may have a maintainance free battery which will make that hard if not impossable to do :?
    C: if the above all checks out get the battery LOAD tested ( any auto elec can do this for you in a few sec's )

    The biggest killer of batterys or bringing up any fault is COLD weather. so i'd be totally isolating the battery as the fault 1st, before looking at the charging system. If the battery checks out then head for the charging system.
  9. Thanks for the info guys :wink: .

    An update..

    The battery had 12.3V, and while running, 14.3V.

    The battery is one of those ones you can't open. There was no sign of corrosion, the leads looked nice.

    I have the service manual so tomorrow I will check the alternator and voltage regulator. I'll keep you posted.
  10. 12.8-13V is actually close to a fully charged battery, so I'd say that's where your problem lays.

    At 14V your charging system is working well.
  11. How old is the battery, do you think?

    Depending on the quality of it and the use that the bike's had, a battery's life can run between say 2 years and 5 years.

    My money's still on the battery being U/S.
  12. The only true way to test a battery is with a hydrometer. Otherwise take a trip down to Batteryworld and they will test it for you for free.
  13. OK.. thanks again for the outstanding info.

    Firstly. How do I make sure the battery is fully charged when I check it? Is a 20-minute ride from work good enough?

    Secondly. I have been fiddling, trying to get to the voltage regulator. I finally got the damn thing out, but I couldn't disconnect it (a) do you need a special tool for that......(b) the service manual recommends using a specific multitester that is supposedly very reliable for honda electrics. Am I wasting my time with a $15 multimeter?

    I am definitely keen to sort it out myself.... but maybe I should just get it looked at next service (it is running AOK now :)) :shock: :?
  14. +1 to Roarin's regulator/rectifier theory, just because it sounds like what was happening before we replaced that in Cheng's Across.
  15. Roarin is spot on, you will be frying your reg/rec.

    I too have replaced a couple on Hondas in the past. If left like this, it will eventually wreck your battery and cause other electrical problems. A typical sign is the brightening of your lights with increasing revs, and not turning over at all sometimes, then not having any problems whatsoever at other times. And yes, it is bloody annoying not knowing when you'll be needing to push start it!

    When faulty they have a hard time regulating the current, this then must be dissipated as heat. Usually they run very warm, but when faulty they can burn! This can sometimes melt the plug to the connector a little: pull harder!

    As well as replacing the reg/rec, many people also replace the plug/wiring, as any damage here can cause the problem to rear up again when it shorts out. Inspect it thoroughly for melted wiring.

    When choosing an aftermarket reg/rec (don't bother with a genuine one, some still fail) make sure that it has generous cooling fins/heatsink capability. Aftermarket ones will also be a bit cheaper. Honda has a poor reputation with reg/recs so I know use R1/R6 units without any problems at all, I also know of at least two others using these.

    A $15 multimeter will do the job fine.
  16. Question related to the reg/rec - is it meant to make any noise when I press the starter?

    Yesterday morning & last night - had to push start it again, same thing this morning. As soon as I got home last night the charge in the battery was 12.4V. This morning it was similar.

    I turned the starter over a few times - the voltage in the battery dipped sharply after a few non-prolonged goes at it, went to 9V pretty quickly. While I was trying to get it going, each time I would press the starter button, the reg/rec was making quite a noticeable electric clicking/sparking sound.

    Is it normal for the reg/rec to do that, or do you think that adds weight to the buggered reg/rec theory?
  17. OK disregard the last post :)

    Clicking noise coming from the starter relay switch (?normal)

    I managed to get the reg/rec out, and stuck in another one. No change. So at this point it seems that theory is on the back burner (ps anyone in Sydney need a cheap Honda reg/rec?? :grin: )

    Before I go and buy a new battery, do starter relay switches commonly have issues?

    Thanks for your attention.
  18. Final update.

    Those who said it was the battery, go to the top of the class.

    As for the reg/rec theory, who knows, that may have been the intial cause, but a new battery seems to have eliminated the issue for the moment.

    Tks for everyone's advice