TM1820 Starter circuit

Harry in Ky · Aug 7, 2024

I think you're finally catching on here. That fuse had no business being there from the start. Whoever put it there didn't know what he was doing.

pycoed · Aug 7, 2024

ponytug said:
Is there a reason to think that this particular starter solenoid would draw less than 25A? i.e. Have you measured the draw? A a rule, at least in my experience, starter solenoids aren't particularly frugal devices.

All the best,

Peter

Clean wire from teminal C on the ignition switch direct to the S terminal on the solenoid.
Turn key: fuse blows.
Found a 40AMP slow blow MAXI fuse & connected that in place of the fuse.
Turn key: fuse blows
I dug out an old ammeter from a box in the garage where it has sat for about 40 years Connected it in place of the fuse. Pulled out stop cable. Turned key - starter turned over normally, ammeter showed 40+amps dropping to 30ish amps while starter turning normally! I'm flabbergasted! There's perhaps a current spike for the pull-in coil to be expected momentarily (thats "FOR a moment" in English rather than "IN a moment" in American!) but 30Amps continuous for a little hold-in coil is ridiculous. There's clearly a starter solenoid fault going on here.
I want to use the tractor today to clear some garden rubbish for the missus & transport it to the firepile (I have a transit box (carry-all in US I believe) which will be just the job for this little beaut.
I'll refit the push button for now & start looking for the right solenoid to order.

ponytug · Aug 7, 2024

Congratulations on tracking the problem down! Great job. Did you try measuring battery to new wire to solenoid, just to rule out the switch?

It is not uncommon for solenoid windings to partially short and that greatly enhances the current draw.

All the best,

Peter

bmaverick · Aug 8, 2024

pycoed said:
Clean wire from teminal C on the ignition switch direct to the S terminal on the solenoid.
Turn key: fuse blows.
Found a 40AMP slow blow MAXI fuse & connected that in place of the fuse.
Turn key: fuse blows
I dug out an old ammeter from a box in the garage where it has sat for about 40 years Connected it in place of the fuse. Pulled out stop cable. Turned key - starter turned over normally, ammeter showed 40+amps dropping to 30ish amps while starter turning normally! I'm flabbergasted! There's perhaps a current spike for the pull-in coil to be expected momentarily (thats "FOR a moment" in English rather than "IN a moment" in American!) but 30Amps continuous for a little hold-in coil is ridiculous. There's clearly a starter solenoid fault going on here.
I want to use the tractor today to clear some garden rubbish for the missus & transport it to the firepile (I have a transit box (carry-all in US I believe) which will be just the job for this little beaut.
I'll refit the push button for now & start looking for the right solenoid to order.

I made mention to test the old solenoid type start for load. Best to replace it with the modern OSGR starter, they draw less power and crank over better.

Here is what a modern OSGR starter is all about.

And the best part is, OSGR last longer and are 2/3rds the price of a solenoid type. Check this out!
Your Yanmar OE p/n is 124250-77012

https://www.amazon.com/Replacement-121120-77010-121370-77020-124250-77012-028000-5730/dp/B017XY46RI

pycoed · Aug 15, 2024

Harry in Ky said:
I think you're finally catching on here. That fuse had no business being there from the start. Whoever put it there didn't know what he was doing.

Ah! I thought the cable connectors looked "factory" to me & I've now found that , although not shown on the wiring diagram, there IS a "fusible link" factory fitted in there.

Fusible Link fits Yanmar YM2001 YM2002 YM2010 YM2020 YM2202 YM2220 YM2301 YM2310 YM2402 YM2420 YM2620 YM2820 YM3220 YM4220 YM4300 FX265 194550-51220

Fusible Link for Yanmar Tractor(s) F46D, F235, F255, FX26D, FX28D, FX32, FX42D, FX235, FX255, FX265, FX285, FX305, FX335, FX435, YM1702, YM1720D, YM1802, YM1810, YM1820, YM2001, YM2002, YM2010. Replaces Yanmar OEM Number(s) 194550-51220, 194312-51220.

www.tractorpartsasap.com

Presumably this had failed at some stage & been replaced by a standard blade fuse.

Harry in Ky · Aug 15, 2024

Not exactly the same thing is it? Some tractors use a standard automotive type slow blow fuse in that spot but it's much heavier than a simple blade fuse. They can be rated for as high as 80 or more amps. That type will support the starter energize circuit.