Battery, Regulator or Alternator?

Simmo

STOC#7892
Joined
Apr 24, 2009
Messages
35
Location
East Devon, UK.
Bike
1999 ST1100AX
STOC #
7892
I have a 1999 ST11AX. On a ride home on Sunday I braked for a speed camera then the bike spluttered, back fired and then the engine cut out. Battery flat, wouldn't turn over the engine. Parked up, waited half an hour and the bike started again. Rode 5 miles and then it did the same thing again. Battery flat, wouldn't turn over the engine. Then I got a recovery out to take me home.

Charged the battery up yesterday and the bike starts fine. This morning the battery was fine and it started OK. Measuring across the terminals with the engine running I get about 12.1V, no change with increase in revs. 12.5V without engine running.

My voltmeter on the dash does not change it's reading with revs.

Could a bad battery cause these readings?
Is it more likely to be alternator/regulator?
Could it just be bad wiring?

I've read lots of past posts but nothing to exactly replicate what happened to me.

If I need to take out the alternator how long should I allow to carry out the work (hours).
 
If you have the bike running and 12.1 volts is all your getting at the battery terminals around 4k rpms, your alternator isn't putting out. I guess it could be a failing battery, but a failing battery usually will not increase it's charge sitting as your's did. you have 12.5 volts with the engine not running. each cell of the battery has 2.1 volts for a total of 12.6. the requirements of the engine running and other loads have brought this down to 12.1 this should be at least 14 volts at 4K rpm

The first thing I would do is do as Karen says, clean the battery terminals.
2nd, take the battery to an auto parts store that can check batteries and make sure the battery is good.

Ralph Sims
 
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the_gr8t_waldo said:
it's more likely that a bad battery is the offender. how old is the battery, anyway?.
Click to expand...

I don't know. It is OEM and was in the bike when I bought it about 6 weeks ago. It doesn't look brand new, so I'll start there.

Ordered, even if it is not the battery best to replace it before it fails... ;)
 
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Irrespective of the battery, that terminal voltage is very low with the engine running.

Make sure you re-check your terminal voltage after installing the new battery AND make sure you fully charge the new battery BEFORE putting it on the bike.

Engine running I would expect at least 13.8Vdc at the terminals with a good battery.
If it is lower, as previously described, then the ACG/rectifier/regulator output is suspect and should be investigated. A good strip and clean of all connections before reconnecting the battery would not go amiss. Also check the fuse in the starter relay for cleanliness and serviceability.
The frame earth/return/negative strap should also be checked for lack of corrosion and tightness.

HTH
 
+1 on the charging circuit or alternator.

A good alt (and wiring) will keep the bike running even if the battery is pretty much dead - your bike died while it was running.
 
Sounds like a bad connection or failing regulator/alt. The regulator is built on to the back of the alt on the post 96 models so you will want to check/confirm all the connections/Fuse/relay before digging into that.
 
You guys, across the pond, have corrosion problems that I haven't heard of over here...
As suggested already I would definitely check the main ground (frame earth I believe is the same) as we had an ST1100 over here that was finally traced to a bad main ground.

Mark
 
Firstpeke said:
Irrespective of the battery, that terminal voltage is very low with the engine running.

Make sure you re-check your terminal voltage after installing the new battery AND make sure you fully charge the new battery BEFORE putting it on the bike.

Engine running I would expect at least 13.8Vdc at the terminals with a good battery.
If it is lower, as previously described, then the ACG/rectifier/regulator output is suspect and should be investigated. A good strip and clean of all connections before reconnecting the battery would not go amiss. Also check the fuse in the starter relay for cleanliness and serviceability.
The frame earth/return/negative strap should also be checked for lack of corrosion and tightness.

HTH
Click to expand...

I get 12.8 on mine. My biggest issue is the connector at the regulator burning, so I removed the connector and put new ends on the wires, cleaned, replugged everything and it's charging fine even at 12.8. My battery was dead the other morning, same symptoms as the first post the previous day. Fixed the wires and everything runs good again. But a 10 year old battery is a candidate for replacement.
 
Like Karen said start with the cheap things first. I'll have the battery tomorrow and while it is charging I can check out and clean all the connectors/earth etc. on the bike.

I did think that it may be partly old spark plugs. I haven't replaced the ones which came in the bike, yet.....
 
Karen said:
I disagree, when I first installed a second set of running lights my alternator lacked the poop to run them and keep my battery charged..... I had to put my battery on a charger every other day to keep it charged. On my way home one night my bike stalled and wouldn't restart. A quick jump had her up and running again. Brought her home put her on the charger and she was good to go.

I replaced the alternator with a 40amp about 6 months later.
Click to expand...

I could be wrong (wouldn't be the first time) but I figured as his is a 99 and would have the 40 amp alt that that should be enough oomph - no mention of extra electrical drains.

Hope we find out
 
Is the main earth the one slightly to the right of th seat lock?

The only other electrical drain could be a digital temperature unit on the accessory shelf (PO) or two driving lights (PO) which only come on with high beam. I haven't ridden the bike during the night yet so I haven't used high beam except for testing if it works.
 
Assuming it was a ten year old battery.......?

New battery (YUASA not Honda badged) I get these readings:

Acid just added after it came out of the box - 12.7V
After full charge (Accumate) 13.35V
Fitted, ignition off 12.9V
Ignition on 12.4V
Idling 12.35V
5000rpm 11.8 - 12.1V

I then found a relay behind the main fuse box which provides power to the digital air temp farkle, driving lights, horn and dash mounted voltmeter. It does click with ignition turned on/off. With the relay's positive feed from the battery disconnected I get a steady 12.4V @ 5000rpm.

All measurements taken across the battery terminals.

At some point in it's life, not now, it has had an audio system fitted (still have aerial in right pannier) and I think possibly an alarm. I still have the controls for the audio on the accessory shelf, the wires have been cut at the control. There are two 'spare' wires under the seat (orange could be yellow (colour blind)), 1 marked "Flasher" and "diode splitter" and the other just loose.

5/6/09
Just done a 50 mile ride with the new battery and the relay feed disconnected - no problems at all, my intermittent ABS rear modulator error didn't occur again either. The ride was a mixture of slow city traffic, motorway and country roads.

BUT

After an hour in the driveway the reading across the terminals is 12.27V with engine off and at idle it is 11.97V.
 
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Local STealer have fitted the new alternator in double quick time but the silencer snapped off on the way home. I knew it was rusty but not that bad. Sounds great unsilenced on one side!

Anyway, quick trip to Halfords for some exhaust repair bandage and it is as good as new, hmmmmmmm ;)

Will hopefully last long enough for me to win one on ebay, just happens to be one on there at the moment....
 
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