28 amp alternator replacement

[jhacruzr]

I have a 1995 ST1100 that runs great with 105,000 miles on the clock. Recently the alternator is not keeping the battery charged. I took it to a local mechanic who is highly respected for his electrical system skills, but has not done a replacement on the ST. He has replaced the regulator/rectifier with no change in voltage output and has concluded the alternator must be replaced. I have read all the posts I could find and do not see one that details the procedure for removing and replacing the alternator. My Haynes manual says the motor has to be removed to access the unit. Is there another less invasive way, and if so could someone detail the procedure? Also, where do I buy a replacement alternator. Any help would be greatly appreciated.
Thanks, Jack

 

[ST1100Y]

Is there another less invasive way...

Yes, accessing it by removing swing-arm and fuel-tank...

Your mech should have checked the alternator output (3-phase) and winding resistance...

Once its confirmed that your stator winding is defective, the question arises if you only replace the 28A stator, or go for the 40A upgrade?

 

[kiltman]

Here are some instructions for the conversion
http://www.st-riders.net/index.php?topic=942.0

 

[jhacruzr]

Thanks for the quick reply. I live in California and do not use any heated gear so my electrical load is no more than stock except for a radar detector. I use the stock lighting. Do you or anyone in the states know the best place to procure a replacement rotor?

 

[Brant]

Yes, accessing it by removing swing-arm and fuel-tank...

Your mech should have checked the alternator output (3-phase) and winding resistance...

Once its confirmed that your stator winding is defective, the question arises if you only replace the 28A stator, or go for the 40A upgrade?

lol....my thoughts EXACTLY. the 'highly respected for electrical skills' was an IMMEDIATE red-flag......no offense intended jhacruzr, just majority of the times, 'par for the course'.

 

[ST1100Y]

lol....my thoughts EXACTLY. the 'highly respected for electrical skills' was an IMMEDIATE red-flag

Yeah... I was hesitant... ;-)
The "...has concluded the alternator must be replaced..." kinda gave it away...

So again: before starting to order expensive spare parts and replacements, I'd cover the basics to eliminate all "simple culprits" first:
- battery tested, fully charged and terminals firmly attached
- voltmeter test on battery terminals: should read between 12.6 to 15.0V (later @ ~5000rpm)
- condition of mains-winding stator connector/plug
- condition of mains wiring
- condition of connectors on bottom of VRR
- conditions of bike wiring harness
any signs of corrosion, overheating, melting or burned wiring must be properly addressed...
Discolouration of the insulation and hardening of the copper strands are clear signs of corrosion caused increase of resistance, thus overheating...

Once any wiring related issues are off the table, continue with measuring resistances
(keep in mind that the 28A alternator is a 3-phase system, thus 3 identical power windings, thus 3 identically readings must be found)
- resistance between the 3 yellow wires: ~4.0 Ohm
- resistance between (any) yellow and ground: infinite
- resistance between (any) yellow and white: infinite
- resistance between (any) yellow and red/white: infinite

Measuring protocol of the VRR is a bit more complex, dunno if the Haynes fully covers it
ID the prongs by the colour of the wires in the big 6 pin connector shell, detach named, then take measurements on the VRR's prongs:
- yellow - red/white: 7.5 Ohm (3x)
- white - red/white: 60 Ohm
- white - yellow: 28 Ohm (3x)
- all other combinations: infinite

Then, to cover all, check the AC output of the alternator:
- detach the yellow 3-pin and the black connector coming from the alternator
- start engine (will now run on battery power only)
- carefully measure the voltage at the 3 stator sided, yellow wires.... IIRC something ~60V AC (set voltmeter accordingly!), and again: must be 100% equal on all 3 windings

 

[wjbertrand]

Thanks for the quick reply. I live in California and do not use any heated gear so my electrical load is no more than stock except for a radar detector. I use the stock lighting. Do you or anyone in the states know the best place to procure a replacement rotor?

I think when you look at the component costs you'll find that the 40A upgrade parts are comparable to the 28A replacement. The upgrade has advantages in reliability, even if you don't need the additional amps. Work wise, you're still going to have to remove the swing arm and fuel tank either way, so not too much difference there either.

 

[Bush]

Do you or anyone in the states know the best place to procure a replacement rotor?

The part is available from Honda, but go to any online OEM retailer for the best price. Partzilla is where I found the best price on a new stator. Although the 40A upgrade does give a better system, for your needs the 28A will last just as well and is a somewhat simpler job than the upgrade.