Jinma Key Switch replacement From NAPA?

[Swampy]

Box says: M-924-BX
Screws are laid out basically just as the diagram provided by TruChaos.

ST = starter solenoid (via the clutch interlock switch)
BAT = 12v from the ammeter
CH = Choke - but it will do just fine connected to the glow plug wire
IGN = ignition. Basically just the ON-ACC position to power things like the instrument panel and battery charging when the engine is running.

I take it these would be the 4 screws that I would use. It seems it should be simple just use the "CH" screw for the glow plugs.

Swampy

 

[greg_g]

Correct, the CH post is where the glow plug wire should go. The -BX suffix is moot, it only denotes a boxed switch (as opposed to bulk).

Let me know if you feel you want to add a glow plug and/or starter relay. I had a Y485 that was a pig to start in the cold, and added both (plus an oil pan heater).

//greg//

 

[Gramps in NM]

Greg, I curious as to the benefit of using a relay setup for either glow plugs or starter. Is it just to protect the switch assy. or does it somehow supply more current?
Gramps

 

[greg_g]

Indirectly, yes. The glow plugs initially represent a fixed resistance. So increasing or decreasing voltage to them increases or decreases amperage. The more amps they get, the hotter they glow. The problem with early Chinese tractors was the wiring was piss-poor. Too much voltage got lost between the battery (through the switch) to the glow plugs. Low voltage delivered means they didn't reach optimal heat. I've seen as little as 7.x volts at the glow plugs (with OE wiring).

A relay in the glow plug circuit all but eliminates that loss. Instead of the keyswitch being connected to the glow plugs, it's connected to the relay instead. Also connected to the relay is 12v straight from the battery and the glow plugs themselves. All that requires is a few feet of 10AWG primary wire and some connector lugs. After that, turning the key to HEAT energizes the relay - which in turn feeds the full 12v direct from the battery, by way of your nice new 10ga wire.

Same problem exists in the wiring to the older model starter solenoids. When a solenoid doesn't get enough voltage, it starts to have problems engaging the pinion and ring gears. A second relay can fix that problem too. I had both on my Y485, plus I added one last piece of 10ga to boost charging voltage to the battery. Think my total investment was under $50

//greg//

 

[California]

Just sticking my nose in here ... I hope somebody doesn't tell me I went and sat in the wrong pew.

Hoyetractor has a replacement switch that I bought for my Yanmar. It has the circuits discussed in this thread, in particular 'glow plug before start' and 'glow plug while cranking'. It doesn't need relays. I've used this since 2004. The quality seems fine.

 

[greg_g]

Good idea. But many switches supply the glow plugs during cranking. This just happens to it externally rather than internally.

//greg//

 

[Gramps in NM]

Thanks for the reply Greg. I understand all you said but it would also seem a person best be careful in the choice of relay due to the substantial amount of current draw across it's contacts. Especially with the glow plugs as an up to 30 second draw (more than once perhaps) at close to 30 amps can generate quite a bit of heat. This is why I thought it might be to protect the switch. My unit is slow to start as the temp. drops so I'm considering the relay as to the plug circuit. But first I need to isolate each plug and test them. Also the injectors may need some attention. Due appreciate the info.

 

[greg_g]

Naw, you're not going to be pullin' anywhere near enough amps to burn up one of these Ford/NewHolland relays. They're common and inexpensive; relay + wire + connector lugs shouldn't run over $20

//greg//

 

[Rich Waugh]

Gramps,

One problem in cold weather is that your battery produces somewhat less current, and if your conductors are marginal then your glow plugs and/or starter solenoid and motor may be operating way below optimum. By using relays for these circuits you can supply them with heavy enough gauge wire to minimize any voltage drop and prevent heat buildup. Heat is a result of resistance and bigger wire means less resistance so less heating in the wire and more heating in the glow plugs.

The relay Greg pictured will easily handle 30 amps and you can get relays to handle up to 100 amps for just a few bucks more. The primary coils in the relays only draw an amp or so to energize them, so there is no voltage drop across the switch contacts as there often is when not using a relay.

 

[Smalljobs]

I use same relay as in Greg's post. It works great here in New England. When it gets really cold it's necessary to use a block heater or a radiator hose heater.