1GM10 Alternator

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The charge light on the panel doesn't go out, but the battery voltage goes up to 14 volts when the engine is speeded up, and so appears to be charging. There are two wires from the alternator to the charge light, one shows battery voltage, but the other only shows 4 to 8 volts depending on speed.
Hitachi 135 alternator. Seeing as it appears to be charging, can I do any harm in ignoring the warning light?
Anybody got any ideas? Could it be diode trouble?
Thanks, Dave

 

[Bunny]

Not an expert, but i believe some alternators have a "warning light simulator" built into them. If this packs up the light comes on, but they still charge. Like i say, no expert but replying to you may spur someone in the know to put us both right. /forums/images/graemlins/ooo.gif

 

[pampas]

suggest thst you remove it and get it bench tested looks like the warning light diode/s has packed up.

 

[William_H]

Some alternators have an additional 3 diodes for providing field current when running. This power takes over form the current through the warning light so extinguishing the warning light.
The question is... does the alternator still appear to charge with the lamp diconnected or removed. If the charging stops then it is relying on the current via the lamp and that is not right. olewill

 

[billcowan]

You can get a replacement alternator from any motor factor for about HALF the cost of a ripoff yanmar one. ie circa £60

I think its the same lug layout as a Honda Civic or somesuch.
The only difference is the pully is marginally bigger, so you need a new belt, £2.50

Part No. is FRA623 longer belt is PWFT725

also oil filter is CRO2071 £2.73

 

[billcowan]

OH yes and if you want the FULL workshop manual for GM Yanmars, you can download it on e-mule or limewire, or PM me

 

[William_H]

High Barnicle just be aware tyhat a larger pulley will give you less RPM on the alternaor. Fine for a petrol engined car which can reach high engine revs but not ideal for a small diesel. So larger pulley may end up with inadequate charge especially at idle. olewill
PS is should be reasonably easy to swap the pulleys.