Electrics problem, suspect Alternator or Rectifier

[sunspark4600]

Hey everyone.
I'm hoping some kind person to tell me how to check my alt & reg/rec using a meter as I think one of them is FUBARED, please include a fairly simple explination as the most leccy complex thing I've done with her is replaced the indicators back to standard ones and changed the battery.
Long Story: After scrimping enough money for a new engine seen as the old one took a fancy to it's valves last August my ZXR400 L1 (import) is back on the road with a freshly serviced L4 engine, all the electrics work ok and when blipping the throttle past the 4000 RPM mark the lights do brighten up a bit more, however, it managed to discharge it's old battery within an hour, which I replaced with a new one as I thought it's probably fooked after being stood for 8 months, yet this one has run out of charge within one hour.

Went out for a quick 30 minute run and popped into a garage to get some redex and cleaning stuff, tried to fire it up and heard nothing put a lethargic churn. :smt013
Have put both batteries on charge on a fancy Optimate charger and both are 100% ok, so I think the issue is the alt or rec/reg unless anyone else has any other ideas?

Thanks in advance to anyone who can help!

[lewisdale]

could possibly have a short somewhere

[RedexRobB]

There is a procedure for checking them in the manual. Simplest way to tell is to put a multi meter across the battery terminals and start the bike, rev it to about 4K and you should see (iirc) 14.4v across the terminals. If not then there is more than likely a problem with the alt/rec which, by the way, is all encompassed in one unit

[sunspark4600]

Cheers for that Rob
Charged the battery (again) brought it home and did the check, it started at 12.72v and fell by .01v every couple of seconds, dialled it to 4k and the voltage kept dropping as usual so it's obviously the alternator, I'll take the fairing off tommorrow and check the alternator wiring as it the alternator cover is from the old engine so I can only assume the guy who fitted the new engine also used the old windings which were working ok, so maybe if I'm lucky he's not connected something up or has pinched a wire *Crosses fingers*.

Thanks guys I'll keep you posted.

[RedexRobB]

id be surprised if its the alternator (meant to say regulator/rectifier is one unit), never heard of one giving any problems but thats not to say they never will.

Your best bet is the reg/rec.

[cargo]

Cheers for that Rob
Charged the battery (again) brought it home and did the check, it started at 12.72v and fell by .01v every couple of seconds, dialled it to 4k and the voltage kept dropping as usual so it's obviously the alternator, I'll take the fairing off tommorrow and check the alternator wiring as it the alternator cover is from the old engine so I can only assume the guy who fitted the new engine also used the old windings which were working ok, so maybe if I'm lucky he's not connected something up or has pinched a wire *Crosses fingers*.

Thanks guys I'll keep you posted.

It's not "obviously" the alternator it could be the alternator it still could also be you rectifer/regulator and check all the related wiring and connectors

[sunspark4600]

I sit corrected.
I'll have a poke around with a torch and a multimeter tommorrow.

[sunspark4600]

Think I found the issue, my alts three black & red wires connect to three yellow wires going to the loom using spade connectors (probably not normal as I know it used to be a race bike), one of said spade connectors was linked to it's yellow wire by about 4 or 5 strands of corroded copper wire, which quickly snapped as soon as I moved it.
The plastic outer has been split a couple of time about 1 inch from the connector and the insulation over the two spade connectors has melted, so I think I may have found my gremlin.
I'll be nicking a set of crimps and connectors from a friend today or tommorrow and I'll trim off the inch of wire which has split and re-crimp a new end, as the rest looks OK.

[sunspark4600]

Problem solved, cut off the inch of dodgy wiring from the loom and crimped some new bullet connectors on each end, am now getting 15.2v at 4000rpm on the battery.

Cheers guys

[parby81]

with bike running, stick multimeters in to two of the black wires from the generator and stick the multimeter on 250v AC. (make sure it is AC). You should get a reading of about 43v. If you do then the generator (alternator) is fine.
Whilst your at check for short circuits at the junction box. Pull out all the fuses and test each side of the fuse connection with the bike on and running. Should be battery voltage and close to 0v (if not 0v) on the other side.