Yanmar 1GM10 alternator.

Thanks for your thoughts, guys. At the moment I"m no further forward. I tried to remove the pulley from the new alternator, so I could switch it for the old one but the nut spin the armature in the pulley. I don't have "windy" tools so it's going back to the supplier. I'll post again as soon as I get a solution, which may yet involve some sort of interrupt. The oil pressure switch on the Yanmar is normally open, but no one has suggested it be integrated in the circuit for the alternator. I'm not sure how that would work, anyway. when the engine isn't running the switch is closed. As soon as the oil pump starts working, it opens. Surely this is the wrong way round to act to prevent the coils activation?
 
Topcat47 said:
Thanks for your thoughts, guys. At the moment I"m no further forward. I tried to remove the pulley from the new alternator, so I could switch it for the old one but the nut spin the armature in the pulley. I don't have "windy" tools so it's going back to the supplier. I'll post again as soon as I get a solution, which may yet involve some sort of interrupt. The oil pressure switch on the Yanmar is normally open, but no one has suggested it be integrated in the circuit for the alternator. I'm not sure how that would work, anyway. when the engine isn't running the switch is closed. As soon as the oil pump starts working, it opens. Surely this is the wrong way round to act to prevent the coils activation?
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Try putting an old belt round the pulley and clamp belt up in vice to grip pulley. Spanner on pulley nut and a sharp tap with hammer to loosen.
 
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I had the alternator off and the pulley in a vice. The pulley remained stationary and the shaft rotated with the nut. I've used that rick n the old Hitachi but the new one wouldn't respond.
 
Problem Solved, thanks to Vehicle Electrics in Birmingham!

This company supplied the "new" Bosch alternator. When I advised them of the problem, they said to return it for a full refund, no questions asked. They also said that if I sent the old one to them they would see if they could refurbish it. Bearing in mind my local auto electrician had already told me it was beyond repair (never mind "economical repair") I had no high hopes but they seemed confident so off it went by courier at their expense. It was turned round in their workshops in four days. I fitted it and it works.

While I was disappointed that the "new" one was pushing out too much power for the engine to drive when cold and at low rpm, I can't fault their response to the problem or their skill in managing to turn round my corroded and inoperable old Hitachi, returning it in much better cosmetic condition that I could have hoped as well as fully functional. I will definitely use this firm again and give them 11/10 for customer service.

If you're in the market for an alternator for a 1GM10, however, and are tempted by these chinese copies, ask for them to be tested before shipping to ensure they are not producing more than the 35amps advertised, and keep the pulley from your old one. There's a hint of the problem in the websites where the alternator is said to be suitable for 1, 2 & 3GM Yanmar engines as the larger engines are supplied with 55amp alternators. Vehicle Electrics have recently expanded into the marine market according to their website and are well worth a call if you're in need.
 
Billjratt said:
If you want to delay the alternator startup, then a switch in series with the ign light is the correct way.
The ign lamp allows/supplies the initial current to energise the alternator field. If it ain't in circuit the alt will not start and the engine can be brought up to a comfortable temperature/speed before the switch is thrown. Another way is to fit a manual regulator to limit the initial draw, but manual stuff gets abused/forgotten about and usually causes more trouble.
You can test the process by just taking out the ign bulb and starting the engine, then (with the engine still running) either replacing it or momentarily shorting the wires to it when you feel the engine can stand the strain.
If you're happy with the outcome, simply fit a switch beside the lamp ( I assume it's in a handy place when you're starting. )
I have to say I'm astounded that engines are marketed to propel boats, but can't swing the alternator - and the manufacturer hasn't provided a normally open oil pressure switch in the alt cct.
My 4108 has one and it's 40 -odd horse!
An enhancement to this system would be another lamp to remind you that you hadn't switched on the alternator yet...
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Just been helping someone to fit a new (to them) engine and wire the alternator as no wiring harness. On this alternator (Hitachi ?) there are two connections to the field coils, the R and L connections, with L being the connection for the light. They would both have to be switched so that there would be no output. The R and L are the connectors on that T shaped cut out in the casing.
 
Modern car alternators produce up to 90% of their rated current at little more than tickover RPM.
That is a problem for a small diesel like the 1GM.
Many of the add-on regulators will not help, as they only boost the normal output, ( the alt's own reg remains in circuit to drive the field) so their soft-start functionality may not do anything other than prevent further boosting.
Taking the warning light out may or may not work.
The light assists starting of the alt, and generally kicks it into life at lower rpm, but alternators will often self start due to the remanant field in the rotor.

Best thing would be for 3GM owners with small, old fashioned alternators to sell them to 1GM owners?
 
I recently found that the gearlever could be in neutral whilst the box had stuck in gear. I spent quite a time troubleshooting the engine's inability to get up to tickover from cold starting before an accidetal blow with a hammer sorted it all out! Just another example of how a fairly small load can stop an engine when truly cold. Once warm it'll restart in gearamd go straight to full revs.

Although the OP has resolved his problem, I couldn't help thinking that a timer circuit operating a solenoid on the excitation wire might be enough to let the engine get up to fast tickover? Wouldn't do anything about residual fields though.

Rob.
 
rob2 said:
I recently found that the gearlever could be in neutral whilst the box had stuck in gear. I spent quite a time troubleshooting the engine's inability to get up to tickover from cold starting before an accidetal blow with a hammer sorted it all out! Just another example of how a fairly small load can stop an engine when truly cold. Once warm it'll restart in gearamd go straight to full revs.

Although the OP has resolved his problem, I couldn't help thinking that a timer circuit operating a solenoid on the excitation wire might be enough to let the engine get up to fast tickover? Wouldn't do anything about residual fields though.

Rob.
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The "problem" only arose when the new alternator was fitted. Now the refurbished old one is in place, the problem doesn't arise. I fitted the engine new and never had a problem with the old Hitachi alternator dragging down the engine so I don't see a problem with it that needs to be fixed.
 
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