YM 1820 Mystery electrical box

[pycoed]

Just taken a couple of pics of the mystery box.(See below) I thought I'd cracked it today by removing & cleaning all the connections on the fuse box & fuses even though they all looked fine (I hate glass fuses, but at least they are better than the old Euro fuzes with exposed fuse links, though give me a blade fuse any day). Voila - all the lights worked correctly!
Then I thought I'd check the clutch safety switch - this as far as I know is the only start-inhibiting switch on this model - I don't think it has the neutral & PTO netral switches as well. I found that the clutch pedal wasn't pushing it far enough make contact. Adjusted it's position, clamped the clutch down & still no signal at the original starter solenoid connection when turning the key (switch is fine). So I started to trace the wires (2 black) from the start terminal on the switch... one of the wires is the black wire which runs into the mystery box! Haven't traced the other yet, but it doesn't connect directly to the clutch switch as I'd expected.
Very interesting to read the magic box may control the thermostart, acting as a timer... I get the red dash light coming on when turning the key back but I haven't checked this box to feel if it starts to buzz or anything. I'll have to leave it for a day or so while I sort the missus' car, but I'll post back when I get some progress...

 

[careyo63]

Turn your key backwards and it puts power to the Thermal start! On the YM2000. The 1820 isn't showing how they done it or what Thermal start setup they used.

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It should be pretty much the same. I don't use it and don't have the fuel cup hooked up! Put fuel to it and it works AIS..

 

[ponytug]

Just taken a couple of pics of the mystery box.(See below) I thought I'd cracked it today by removing & cleaning all the connections on the fuse box & fuses even though they all looked fine (I hate glass fuses, but at least they are better than the old Euro fuzes with exposed fuse links, though give me a blade fuse any day). Voila - all the lights worked correctly!
Then I thought I'd check the clutch safety switch - this as far as I know is the only start-inhibiting switch on this model - I don't think it has the neutral & PTO netral switches as well. I found that the clutch pedal wasn't pushing it far enough make contact. Adjusted it's position, clamped the clutch down & still no signal at the original starter solenoid connection when turning the key (switch is fine). So I started to trace the wires (2 black) from the start terminal on the switch... one of the wires is the black wire which runs into the mystery box! Haven't traced the other yet, but it doesn't connect directly to the clutch switch as I'd expected.
Very interesting to read the magic box may control the thermostart, acting as a timer... I get the red dash light coming on when turning the key back but I haven't checked this box to feel if it starts to buzz or anything. I'll have to leave it for a day or so while I sort the missus' car, but I'll post back when I get some progress...
View attachment 883500View attachment 883501

I'm glad that the wiring is mostly ok.
You might want to look at a YouTube video of the thermostart.
Quick:

Longer:

(Skip to the almost the end to see the ignition.
Basically, a coil gets red hot, the heat opens a valve to dribble in some diesel fuel that ignites and burns, warming the intake manifold. When the ignition switch moves from preheat to start, voltage to the thermostart goes off. I believe that the box has a relay and timer to prevent the thermostart from being on too long. As you can tell, it would not do anything very productive to be on while cranking, unlike glow plugs or electric intake heaters.

Good luck on the MOT testing.

All the best,

Peter

 

[pycoed]

I've just found a wiring diagram for a YM 2420 that seems to have this box in the circuits (it's a lot clearer than the one for the 1820).It seems to connec to the little red light & what might be the thermostart. Does anyone have a wiring diagram in English for this model they could post ?

 

[bmaverick]

I've just found a wiring diagram for a YM2420 that seems to have this box in the circuits (it's a lot clearer than the one for the 1820).It seems to connec to the little red light & what might be the thermostart. Does anyone have a wiring diagram in English for this model they could post ?

You need this doc off of the YTOG. Our team put this together just for the reason of using it as a deciphering tool for the Gray Market machines to compare the English model schematics to the Japan ones.

YANMAR ELECTRICAL SCHEMATICS YM 3-DIGIT MODELS R3.pdf

Here are some examples towards a YM1802

YM1802 Headlamp to switch

YM226 Headlamp to switch that matches

 

[pycoed]

I'm glad that the wiring is mostly ok.
You might want to look at a YouTube video of the thermostart.
Quick:

Longer:

(Skip to the almost the end to see the ignition.
Basically, a coil gets red hot, the heat opens a valve to dribble in some diesel fuel that ignites and burns, warming the intake manifold. When the ignition switch moves from preheat to start, voltage to the thermostart goes off. I believe that the box has a relay and timer to prevent the thermostart from being on too long. As you can tell, it would not do anything very productive to be on while cranking, unlike glow plugs or electric intake heaters.

Good luck on the MOT testing.

All the best,

Peter

Yeah _ I know about Thermostarts - I had one on a UTB 445DT & still have a new one in it's box in my garage (was the wiring to the thing was dead on the UTB, not the TS)

You need this doc off of the YTOG. Our team put this together just for the reason of using it as a deciphering tool for the Gray Market machines to compare the English model schematics to the Japan ones.

YANMAR ELECTRICAL SCHEMATICS YM 3-DIGIT MODELS R3.pdf

Here are some examples towards a YM1802

YM1802 Headlamp to switch
View attachment 883566

YM226 Headlamp to switch that matches
View attachment 883567

I'll have a look for that - thanks!

 

[pycoed]

I'll have a look for that - thanks!

The search on the YTOG doesn't return any file found for that & I couldn't find it in the Resources section either - any direct link available? TIA

 

[California]

I see Wi1-07 in your photo. Searching that # online one guy says it is the turn signal flasher on a Yanmar, in an old TBN thread. But there's no additional detail in that thread.

A post on a boating site says Wi1-05 is the engine alarm, for low oil pressure etc.

https://www.sailnet.com/threads/engine-alarm-buzzer.24298/

your buzzer model is WI1-05. Its one input and 3 output (negative as return) via 3 diodes. If the other two alarm works, then its probable the 3rd diode is faulty. You could wire two diodes to one of the working output thus making it as 2 circuit. That should solve your problem. When activated, the positive passes through the buzzer diode, then through to 1 of the new diodes to say Oil Pressure switch or Sail Drive Unit switch then to ground (negative). The buzzer maybe just alittle softer as there'll be 1.2V drop across the series diodes but I guess it won't affect much. The Hitachi buzzer doesn't come cheap. [$150+ in 2006]

I didn't research this any farther but searching "Hitachi Wi (letter i, not numeral 1) 1-0" should find more information.

If it is either a turn signal flasher, or a boating dashboard alarm, it doesn't sound essential so long as you have oil pressure and temp gauges or idiot lights.

​

 

[pycoed]

I've realised that it is in fact WI1-07 rather than W11- I found an old post from Winston back in 2012 that described it & it is in fact a timer for the thermostart as he suggested, fair does!
I tried holding the key in the TS position today & the red TS indicator light goes off after about 20 secs.
Thanks for looking - I should have seen that - I blame failing eyesight after 74 years of abusing it!
I now know this box is working, & all I have left to trace is why the ignition switch doesn't seem to send a signal to the solenoid in the Start position - I think I need to prove the wires from solenoid to clutch switch & clutch switch to ignition. I'm beginning to suspect mousie may have been nibbling somewhere along the line , though to be fair, the loom & the whole tractor is in VG condition for its age, which is why this little problem is nagging at me

 

[ponytug]

I've realised that it is in fact WI1-07 rather than W11- I found an old post from Winston back in 2012 that described it & it is in fact a timer for the thermostart as he suggested, fair does!
I tried holding the key in the TS position today & the red TS indicator light goes off after about 20 secs.
Thanks for looking - I should have seen that - I blame failing eyesight after 74 years of abusing it!
I now know this box is working, & all I have left to trace is why the ignition switch doesn't seem to send a signal to the solenoid in the Start position - I think I need to prove the wires from solenoid to clutch switch & clutch switch to ignition. I'm beginning to suspect mousie may have been nibbling somewhere along the line , though to be fair, the loom & the whole tractor is in VG condition for its age, which is why this little problem is nagging at me

It is very easy for one or two poor connections to reduce the voltage from the switch to the starter solenoid to the point where the solenoid doesn't function. I've sprayed carb cleaner through starter switch keyholes more than once. I usually follow it up with some DeOxIt as a contact cleaner, and general purpose anti corrosion spray. I use DeOxIt on connectors routinely. I suspect wet West Wales is a challenging environment for wiring harnesses...

All the best,

Peter