YM186D starting/voltage problem

[old grayfellow]

Well I got a can of CRC and did the spraying into ignition switch, working the key back and forth, blowing out the CRC. Repeated this process 4-5 times. At first, the solvent coming out on my glove was pretty dirty.

However after this cleaning, problem persists. In fact (strangely), the only change that happened was that the voltages at several of the terminals actually went DOWN from what it was before the cleaning. Before (B), they read ~3v, but After cleaning (A), they only read about 1.2v now. This is only when the key is held in the start (momentary) position. This picture summarizes:

So it appears that while terminal B always has 12.6v (as it should) and terminal BR has 12.6v when key is turned to "on", both of these terminals drop to 1.2v when the key is on start. Then they return to 12.6v when i release it.

 

[bmaverick]

Well I got a can of CRC and did the spraying into ignition switch, working the key back and forth, blowing out the CRC. Repeated this process 4-5 times. At first, the solvent coming out on my glove was pretty dirty.

However after this cleaning, problem persists. In fact (strangely), the only change that happened was that the voltages at several of the terminals actually went DOWN from what it was before the cleaning. Before (B), they read ~3v, but After cleaning (A), they only read about 1.2v now. This is only when the key is held in the start (momentary) position. This picture summarizes:

View attachment 864820

So it appears that while terminal B always has 12.6v (as it should) and terminal BR has 12.6v when key is turned to "on", both of these terminals drop to 1.2v when the key is on start. Then they return to 12.6v when i release it.

You could just replace it.
Amazon.com

 

[California]

I like the idea of measuring voltage at that switch input terminal when some additional load is temporarily jumpered to that same terminal.

If voltage drops to 3v when that load is applied then the switch isn't receiving full voltage when under load so find the cause for that.

If the input voltage remains high, replace the switch. Under $20, NBD.


BTDT. I tore open the old switch that had worked only intermittently when I bought the YM240 (YM2000), and found the switch was packed solid with dead pillbugs.

Not relevant when the output voltage from your switch is 3v, but here's another starter frustration maker: In addition to the clutch safety switch, on YM186D there's a second safety switch beneath the seat that requires the PTO lever to be at neutral for current to pass to the starter solenoid. A few times rototilling I have wondered why I can't restart the engine, before remembering that PTO switch.

 

[old grayfellow]

Yeah, this drop in voltage from 12v-->1.2 when I turn the key to start (i.e. create a kind of load) *even measured at terminal B ("battery") makes me think possibly the problem is not in the switch at all, but maybe something upstream.
According to this diagram (if I understand it correctly), the power to "B" on the ignition switch comes not directly from the battery (as you would think), but appears like it comes through the voltage regulator first. (See the dashed red line):

If so, perhaps the voltage regulator is faulty, not allowing enough voltage/current to flow?
Note: I did have to replace the voltage regulator some years ago.. maybe the replacement has also gone bad?

So I tested the VR. Result: VR fails.

So looks like I'll have to order another one.

 

[old grayfellow]

Yeah, this drop in voltage from 12v-->1.2 when I turn the key to start (i.e. create a kind of load) *even measured at terminal B ("battery") makes me think possibly the problem is not in the switch at all, but maybe something upstream.
According to this diagram (if I understand it correctly), the power to "B" on the ignition switch comes not directly from the battery (as you would think), but appears like it comes through the voltage regulator first. (See the dashed red line):

View attachment 865068


If so, perhaps the voltage regulator is faulty, not allowing enough voltage/current to flow?
Note: I did have to replace the voltage regulator some years ago.. maybe the replacement has also gone bad?

So I tested the VR. Result: VR fails.

View attachment 865118

So looks like I'll have to order another one.

Received the new voltage regulator.
Before installing, I did the above continuity tests on it.
Result: The brand new regulator also had no continuity between any of the wire combinations that were supposed to have continuity according to the above chart. Plugged it in on the tractor and tried the starter.. same problem as before.

So what to conclude?

-The new one is faulty?
-The continuity chart is perhaps not applicable to "modern" voltage regulators (if they have a different design or something)?
-The starting problem was never the voltage regulator but is something else?

On the VR testing though, the new (and older) VRs i bought are stated in the sales listing to be for my YM186, and the plug and wire colors match the old one (and also match the wire colors in the test chart above) exactly.

Running out of ideas, I checked the battery ground wire again, looked OK, re-greased and tightened both ends. Still no joy.

Running out of ideas, I noticed the 6-wire multi-pin connector plug for the voltage regulator looked a bit dirty, so cleaned it out with the CRC spray. BINGO. Started right up. And that was with my old VR installed (so it wasn't bad after all).
Still don't understand the VR continuity test results, but perhaps modern replacement VRs have a different kind of circuitry than the originals that the troubleshooting continuity test was designed for.

Hopefully this episode will furnish "one more thing to check" for anybody who has a similar problem (or myself in a few years when I forget what the solution was..)

 

[rScotty]

Received the new voltage regulator.
Before installing, I did the above continuity tests on it.
Result: The brand new regulator also had no continuity between any of the wire combinations that were supposed to have continuity according to the above chart. Plugged it in on the tractor and tried the starter.. same problem as before.

So what to conclude?

-The new one is faulty?
-The continuity chart is perhaps not applicable to "modern" voltage regulators (if they have a different design or something)?
-The starting problem was never the voltage regulator but is something else?

On the VR testing though, the new (and older) VRs i bought are stated in the sales listing to be for my YM186, and the plug and wire colors match the old one (and also match the wire colors in the test chart above) exactly.

Running out of ideas, I checked the battery ground wire again, looked OK, re-greased and tightened both ends. Still no joy.

Running out of ideas, I noticed the 6-wire multi-pin connector plug for the voltage regulator looked a bit dirty, so cleaned it out with the CRC spray. BINGO. Started right up. And that was with my old VR installed (so it wasn't bad after all).
Still don't understand the VR continuity test results, but perhaps modern replacement VRs have a different kind of circuitry than the originals that the troubleshooting continuity test was designed for.

Hopefully this episode will furnish "one more thing to check" for anybody who has a similar problem (or myself in a few years when I forget what the solution was..)

I didn't see whether you disconnected all the circuits before testing the voltage at the ignition switch. You cannot test voltage there if the solenoid is still connected.
When a solenoid clicks but the starter doesn't turn, it's a sure sign that the contacts in the solenoid need to be filed or cleaned. If not that, the brushes in the starter need replacing. You can make a set of brushes to fit using any brush set that is close dimensionally with a bit of sanding and filing.

None of what you originally said would have pointed me toward the ignition switch as the culprit - although it is true that the ignition switches do corrode over time, and work on them is never wasted..
rScotty

 

[old grayfellow]

I didn't see whether you disconnected all the circuits before testing the voltage at the ignition switch. You cannot test voltage there if the solenoid is still connected.

Yes I had disconnected the solenoid trigger wire from the solenoid. Actually the first thing I did was to disconnect that wire and test for voltage (the voltage that would be reaching the solenoid) when I turned the key to "start". At first that voltage was ~3v and climbed a bit, and after cleaning the ignition switch it went down to only ~1.2v. I guess neither of those was enough volts to trigger the solenoid to even click.

When a solenoid clicks but the starter doesn't turn, it's a sure sign that the contacts in the solenoid need to be filed or cleaned. If not that, the brushes in the starter need replacing. You can make a set of brushes to fit using any brush set that is close dimensionally with a bit of sanding and filing.

Yes if the solenoid had clicked I would've looked into the contacts inside or the starter itself, but there was no click, no nothing, just silence.

None of what you originally said would have pointed me toward the ignition switch as the culprit - although it is true that the ignition switches do corrode over time, and work on them is never wasted..

It does seem like cleaning the ignition switch made a little difference in voltage, but no it wasn't the problem (well at least I didn't needlessly buy another ignition switch). Since the only thing that fixed the issue was cleaning the 6-wire plug connector (and seems to have fixed it completely), I'm guessing that connector was so fouled that it was only letting a little bit of voltage through (at least "under load" when I turned the switch to start). After cleaning the plug and plugging it back in I checked for voltage at the solenoid trigger wire and found it was now 12v with key at "start", so plugged it back onto solenoid and yup it started normally.

But since that connector was upstream of the ignition switch in the path of power (i.e. battery--> connector/VR --> Ignition switch --> solenoid) it seems to confirm that power has to flow through the VR for the switch/solenoid to accomplish starting the engine. I wouldn't have guessed that, but that's also what the wiring diagram seems to show.

Thanks to everyone for the suggestions.

rScotty

 

[rScotty]

Yes I had disconnected the solenoid trigger wire from the solenoid. Actually the first thing I did was to disconnect that wire and test for voltage (the voltage that would be reaching the solenoid) when I turned the key to "start". At first that voltage was ~3v and climbed a bit, and after cleaning the ignition switch it went down to only ~1.2v. I guess neither of those was enough volts to trigger the solenoid to even click.

Yes if the solenoid had clicked I would've looked into the contacts inside or the starter itself, but there was no click, no nothing, just silence.

It does seem like cleaning the ignition switch made a little difference in voltage, but no it wasn't the problem (well at least I didn't needlessly buy another ignition switch). Since the only thing that fixed the issue was cleaning the 6-wire plug connector (and seems to have fixed it completely), I'm guessing that connector was so fouled that it was only letting a little bit of voltage through (at least "under load" when I turned the switch to start). After cleaning the plug and plugging it back in I checked for voltage at the solenoid trigger wire and found it was now 12v with key at "start", so plugged it back onto solenoid and yup it started normally.

But since that connector was upstream of the ignition switch in the path of power (i.e. battery--> connector/VR --> Ignition switch --> solenoid) it seems to confirm that power has to flow through the VR for the switch/solenoid to accomplish starting the engine. I wouldn't have guessed that, but that's also what the wiring diagram seems to show.

Thanks to everyone for the suggestions.

Glad it is fixed, that is a real nice summary. In fact, I'm thinking this entire thread is one that we should keep and refer to. It's good fault-tracing technique in spite of my own missed diagnosis.
rScotty.

 

[California]

Agree, these threads where an owner tries everything to solve a mystery, are a valuable resource for someone facing a similar problem in the future.

 

[boatmoter]

My 186D has for some years had this thing where when I turn the key sometimes I'll just hear the solenoid click but the starter doesn't engage, but if I try the key again 1-3 times it would always eventually engage the starter and the engine would start. Kind of an annoyance but it would always start after a few tries so I didn't track down the problem. A couple years ago I had the feeling it might've been dirty contacts or something in the ignition switch so I took that off and cleaned it all up, no change.

But since yesterday, it has gone to a new level of problem; basically the solenoid doesn't even click, just nothing. I cleaned the battery terminals thoroughly and greased them, and tightened well, but no improvement. Battery voltage is 12.7.

So first I tested voltage at the "trigger wire" on the solenoid. I expected ~12V when key is turned to "start", but it only showed around 3.6V. If I held the key in the start position, voltage would climb gradually over 10 seconds or so, but would only reach about 5.1 volts. So if i'm assuming correctly that the solenoid wire should be supplying 12V looks like this might be the issue (insufficient voltage to trigger the solenoid).

But from this point I'm not clear on why there would be this low voltage. I have some info from a service manual on testing the solenoid, but looks to me like the problem might be upstream of the solenoid.

Found an electrical diagram here: yanmar ym186D \\ circuit diagram
and from what I can see it looks like there should be nothing between (12V) power from the ignition switch and the solenoid except the "safety switch" (which has long been defeated/bridged on my tractor).

So I'm left thinking that it must be a dirty connection somewhere between the ignition switch and the solenoid, though it seems odd that there would be a much reduced voltage (3.6-5V) but consistent.

Am I missing something? Any suggestions?

when it is not turning over, have someone hold the key on to start and tap the casing of the starter with a piece of metal, if it turns over, it's the brushes worn out or has dirt on them restricting their movement, if the stater motor has a problem the solenoid will act like that since the coil of the solenoid is grounded by the brushes