Yanmar idiot lights - Part 2

[steve77]

A few weeks ago we had a thread on the Yanmar warning lights and alarms. After reading this thread I decided to finally figure out why my alarm and warning lights had stopped working.

Our engine is for the Genset, and is a 3GMFL-G1. The panel has warning lights for loss of charging, low oil pressure, and high cooling water temp. The alarm sounds for the last two, but not for loss of charging.

We have owned our boat ten years and all during that time the lights illuminate and the alarm sounds each time the key is turned on and before the engine is started. As mentioned in the previous thread, this gives assurance that the lights and alarm are working. Recently, with the key on and engine not running, our alarm has stopped sounding and the cooling water and oil pressure lights do not illuminate.

During troubleshooting, I found that the oil pressure switch and possibly the cooling water switch have failed. BUT, I also found that the wiring from these two switches were crimped together at the engine. Thus, for example, if the oil pressure switch were to detect low pressure, BOTH the oil pressure and cooling water temp lights would come on, as well as the alarm.

I separated the wires so that each sensor only feeds its respective warning light. But it got me thinking, and if you've read this far, this is my question. How does the cooling water switch work? From the wiring diagram it appears that it sends a ground to the control panel under high cooling water temperature to illuminate the warning light and sound the alarm. If so, the only time that light would illuminate is with a high temperature in the cooling water. It will not illuminate when the key switch is first turned on.

This is counter to the discussion we had a few weeks back. Anyone have an explanation of why the cooling water light would come on with the engine not running? How do you get a ground to that light unless there is actually an over temperature condition?

Thanks!

Steve

[Wotname]

Originally Posted by steve77

........

I separated the wires so that each sensor only feeds its respective warning light. But it got me thinking, and if you've read this far, this is my question. How does the cooling water switch work? From the wiring diagram it appears that it sends a ground to the control panel under high cooling water temperature to illuminate the warning light and sound the alarm. If so, the only time that light would illuminate is with a high temperature in the cooling water. It will not illuminate when the key switch is first turned on.

This is counter to the discussion we had a few weeks back. Anyone have an explanation of why the cooling water light would come on with the engine not running? How do you get a ground to that light unless there is actually an over temperature condition?

Thanks!

Steve

In essence, you correct in that the temperature light will only illuminate when there is a over heat condition BUT some instrument panels do provide a test condition to the temperature light when the engine is turned on (but before it has started) in order to check that the lamp hasn't blown. This is not universal - it depends on who/when the instrument panel was made.

If you have a wiring schematic or a link to one, we can work out what your panel should do.

[steve77]

Thanks, Wotname. Here is a photo of the wiring diagram. Hopefully it's legible.

By the way, I found that the wires had been crimped together when I was troubleshooting the oil pressure switch. When I shorted around the oil pressure switch to ground, the alarm sounded and BOTH the oil pressure and cooling water temp lights came on. Same thing when I shorted around the cooling water temp switch.

Take a look at the diagram and see what you think. Welcome to have another pair of eyes!

The diagram tells me that the cooling water temp switch makes contact to ground at some temperate setpoint for high temp. Otherwise it is open. Thus, the cooling water temp light won't illuminate during engine startup, or anytime other than a high cooling water temperature condition.

Let me know what you think. I may be out of touch for a few days as we head to Sardinia. Cheers!

Steve

[Wotname]

Originally Posted by steve77

Thanks, Wotname. Here is a photo of the wiring diagram. Hopefully it's legible.

By the way, I found that the wires had been crimped together when I was troubleshooting the oil pressure switch. When I shorted around the oil pressure switch to ground, the alarm sounded and BOTH the oil pressure and cooling water temp lights came on. Same thing when I shorted around the cooling water temp switch.

Take a look at the diagram and see what you think. Welcome to have another pair of eyes!

The diagram tells me that the cooling water temp switch makes contact to ground at some temperate setpoint for high temp. Otherwise it is open. Thus, the cooling water temp light won't illuminate during engine startup, or anytime other than a high cooling water temperature condition.

Let me know what you think. I may be out of touch for a few days as we head to Sardinia. Cheers!

Steve

Yep, your understanding is correct . This is standard setup for older Yanmars and the only way to test the cooling water temperature switch is to remove it and heat it up in some water. It should remain open circuit until the contacts close at the preset temperature.

[Wotname]

Originally Posted by steve77

Thanks, Wotname. Here is a photo of the wiring diagram. Hopefully it's legible.

By the way, I found that the wires had been crimped together when I was troubleshooting the oil pressure switch. When I shorted around the oil pressure switch to ground, the alarm sounded and BOTH the oil pressure and cooling water temp lights came on. Same thing when I shorted around the cooling water temp switch.
........

Crazy what some POs do

[Wotname]

BTW, it is easy enough to modify the alarm wiring so that the temperature lamp is tested (i.e. illuminates) each time the engine is started. Let us know if you want more details.

Note, testing the switch is not so easy

[Cadence]

Originally Posted by steve77

A few weeks ago we had a thread on the Yanmar warning lights and alarms. After reading this thread I decided to finally figure out why my alarm and warning lights had stopped working.

Our engine is for the Genset, and is a 3GMFL-G1. The panel has warning lights for loss of charging, low oil pressure, and high cooling water temp. The alarm sounds for the last two, but not for loss of charging.

We have owned our boat ten years and all during that time the lights illuminate and the alarm sounds each time the key is turned on and before the engine is started. As mentioned in the previous thread, this gives assurance that the lights and alarm are working. Recently, with the key on and engine not running, our alarm has stopped sounding and the cooling water and oil pressure lights do not illuminate.

During troubleshooting, I found that the oil pressure switch and possibly the cooling water switch have failed. BUT, I also found that the wiring from these two switches were crimped together at the engine. Thus, for example, if the oil pressure switch were to detect low pressure, BOTH the oil pressure and cooling water temp lights would come on, as well as the alarm.

I separated the wires so that each sensor only feeds its respective warning light. But it got me thinking, and if you've read this far, this is my question. How does the cooling water switch work? From the wiring diagram it appears that it sends a ground to the control panel under high cooling water temperature to illuminate the warning light and sound the alarm. If so, the only time that light would illuminate is with a high temperature in the cooling water. It will not illuminate when the key switch is first turned on.

This is counter to the discussion we had a few weeks back. Anyone have an explanation of why the cooling water light would come on with the engine not running? How do you get a ground to that light unless there is actually an over temperature condition?

Thanks!

Steve

I would appear you answered your own question. It was coming on as a result of the oil pressure sensor not the temp. sensor since they were tied together. The oil sensor is normally closed the temp is normally open.

[Cadence]

Originally Posted by Cadence

I would appear you answered your own question. It was coming on as a result of the oil pressure sensor not the temp. sensor since they were tied together. The oil sensor is normally closed the temp is normally open.

PS, they probably did it that way so you would know the water temp. light bulb was working.

[steve77]

Originally Posted by Cadence

PS, they probably did it that way so you would know the water temp. light bulb was working.

Ok, in Sardinia and back online...

I think you are correct. The crimp that connected the oil pressure and cooling water wiring together was located in the wiring harness and covered by electrical tape. The tape looked like original factory work - it was done much more neatly than you see from normal boat work. The harness was then spray painted Yanmar silver, again something that boat mechanics just don't do. It looked like this is the way the engine was delivered. But it doesn't match the wiring diagram.

But now that I have separated the wires, the only time the cooling water temp light will come on is in an actual overtemp condition. In other words, hopefully never.

And this is counter to our discussion a couple of weeks ago where pretty much everyone said that these lights will always illuminate when the key is turned on. I would be interested if other owners of Yanmars have done the same test I did - short the cooling water sensor wiring to ground and see if only the cooling water light comes on, or does the oil pressure light illuminate also? This may be normal for these engines, just not shown on the wiring diagram.

Cheers!

Steve

[Wotname]

Originally Posted by steve77

Ok, in Sardinia and back online...

I think you are correct. The crimp that connected the oil pressure and cooling water wiring together was located in the wiring harness and covered by electrical tape. The tape looked like original factory work - it was done much more neatly than you see from normal boat work. The harness was then spray painted Yanmar silver, again something that boat mechanics just don't do. It looked like this is the way the engine was delivered. But it doesn't match the wiring diagram.

But now that I have separated the wires, the only time the cooling water temp light will come on is in an actual overtemp condition. In other words, hopefully never.

And this is counter to our discussion a couple of weeks ago where pretty much everyone said that these lights will always illuminate when the key is turned on. I would be interested if other owners of Yanmars have done the same test I did - short the cooling water sensor wiring to ground and see if only the cooling water light comes on, or does the oil pressure light illuminate also? This may be normal for these engines, just not shown on the wiring diagram.

Cheers!

Steve

My 2002 2GM20 with Yanmar wiring harness did not have the cooling temp and oil pressure wires spliced together.

The alarm lights behaved as per the schematic i.e. only the oil pressure illuminated prior to start up. The cooling temperature light only illuminated when the sensor/switch was shorted to the engine block.

A previous late 80's 2GM20 was also the same.

[four winds]

on the 3gm30f engine panel there is a toggle switch that turns on the tach illumination.

If one flips this double throw switch the other direction it self tests the warning light bulbs. This allows for a water temp bulb test. Leaving only the temp sender/switch untested before startup.

First I've heard of the wires joined in the harness. Mine is not.

[steve77]

Originally Posted by four winds

on the 3gm30f engine panel there is a toggle switch that turns on the tach illumination.

If one flips this double throw switch the other direction it self tests the warning light bulbs. This allows for a water temp bulb test. Leaving only the temp sender/switch untested before startup.

First I've heard of the wires joined in the harness. Mine is not.

Okay, thanks FourWinds. And thanks to Wotname! Maybe my engine is an outlier. Not the first time!

Cheers!

Steve

[Wotname]

FWIW, I always found the Yanmar wiring schematic to correctly represent the actual wiring but I suppose one should "never say never" and certainly stuff changes over long model runs. Online information doesn't always match the operation and/or service manual that pertains to any particular year model.

[S D Sailor]

Thank you all for this thread....I'm going to look for the original (part one) in the morning....
Questions: four winds - the toggle to test idiot lights on your 3GM30F was located where? (or are you speaking of the "glow"/start rocker?)
Wotname - how would you modify the alarm circuitry to allow for 'testing' of the idiot light/alarm for water temp?
Thanks in advance....(and keep up the good work)...

[four winds]

Originally Posted by S D Sailor

Thank you all for this thread....I'm going to look for the original (part one) in the morning....
Questions: four winds - the toggle to test idiot lights on your 3GM30F was located where? (or are you speaking of the "glow"/start rocker?)
Wotname - how would you modify the alarm circuitry to allow for 'testing' of the idiot light/alarm for water temp?
Thanks in advance....(and keep up the good work)...

On the 3gm30f there are no glow plugs so no switch for that. On the factory engine panel there is a double pole double throw (DPDT) switch next to the buzzer. edit... Maybe SPDT, can't remember, but it's a odd bird because....

Flip it one way and it turns on the tach illumination, flip it the other and it self tests all the warning light bulbs. It's a momentary switch in this position and springs back when released. Handy for the temp bulb test since that bulb doesn't illuminate during normal starting procedures.

This tests the bulbs and sockets, and even the integrity of some connections and wires. But it says nothing about the sender/switches or the connection at them.

If this makes sense, I think it shows that the factory setup does test the temp bulb. At least if the operator chooses to do so with the toggle.