Volvo D1-30

[ShaktisBoy]

Quick question. We had the temp alarm sound on our port engine the other day after a very short period of motoring. My first thought was raw water flow restriction. Raw water not restricted at all. Second thought fresh water side flow or thermostat failure. Flushed the entire system removed heat exchanger stack and all passages clear no restrictions. Tested thermostat in hot water and it opens at 85-90 C.
I put the system back together and started the engine and had an immediate temp alarm suggesting the sensor has failed. I removed the plug on the thermo monitor “item 6 on the diagram below and the alarm quits of course.” Above that thermo monitor is a temp sensor. Can anyone confirm the function of these two parts? It is my belief that the temp sensor item 4 will shut down the engine if it gets too hot, and the monitor triggers the alarm at the helm. Do I have it right?

[donradcliffe]

I don't know if the sensors will shut down the engine, probably not.

I do know that in situations like this my first step is to take out my IR temperature gun and point it at the sensor. The last case was a Yanmar sensor that was reading 30 degrees C too high.

[ShaktisBoy]

Thanks pulling out the IR gun now. There is a single wire running from the EMP sensor #4 to the relay box which is why I’m assuming it will shut down the engine if it gets too hot.

[DougR]

The temperature switch is designed to close to ground if the engine overheats, driving the audible alarm system and lighting the over temp light. You can test the audible portion of this system by pressing the test button. ..Or you can pull the wire off the switch and ground it and see that the alarm activates.

The temp sender is there to drive a temperature gauge. There may or may not be a temp gauge installed depending on which instrument panel the boat builder installed.

Neither of these senders or switches is designed to shut down the engine. Volvo Penta's philosophy is to never have automatic shutdown on propulsion engines as the engine might shutdown in a location which could place the vessel in danger. It's always better to have the shutdown decision in the hands of the skipper. Genset engines...yes. Propulsion...no.

DougR

[redbeard1]

ShaktisBoy - Hello. Just a question to clarify. You wrote that the alarm turned off when you disconnected #6. Could it have been #4 you disconnected that caused the alarm to turn off?

I have a volvo penta 2003 that also has an on-off sensor for temperature alarm (like your #4) and a sensor that transmits data to the temperature gauge (like your #6). Assuming the wiring is similar, disconnecting #6 should not turn off your audible alarm.

I only mention this because when I try to debug electric stuff, it helps to begin with as much certain information as possible.

I guess it is possible your #6 feeds the alarms as well. I'll see if I can find a wiring diagram for your model.

[ShaktisBoy]

Unplugging #4 nothing changes alarm continues. Unplugging #6 alarm ceases. IR gun shows 88 to 91 C on all areas of the heat exchanger after running the engine up to temperature.

[donradcliffe]

Volvo likes to run those engines warm. You might see what temp the switch actuates at. Maybe someone put in a 195-200F switch and you need a 210F

[ShaktisBoy]

Maybe. We have had the boat for 5 years and this is recent. I’m just having a tough time wrapping my head around how exactly the sensor fails. The contacts look clean on both ends.

[kmacdonald]

I'd say just change the sensor to see if it fixes the problem but at Volvo prices that might require a second mortgage.

[redbeard1]

Hi,

Before buying another sensor, why not try using the same sensor from the starboard engine.

Also, cleaning the contacts may not work. As Doug wrote, the sensor is used to complete the circuit and sound the alarm. Inside the sensor, when the right condition is met - temp over x degrees, something moves (sorry for not being more specific. I've never taken one apart and am not sure how the switch is constructed) and allows current to pass from the end of the sensor that is connected to the wire to the end of the sensor that is attached to the engine. This circuit completion allows current to flow through your speaker and makes the sound. If you are hearing the sound, and your engine is not in fact overheating, there is a chance the internals of the sensor have gone bad and the sensor is now completing the circuit at some other temperature.

[DougR]

Just checked the wiring schematic and it shows that #6, with the two wire connector and brown/ white wire, is the alarm switch . Removing the connector from its position on the switch will stop the alarm. Shorting the two wires in the connector together should also cause the alarm to sound. Item #4 with the single light brown wire is there to drive a temp gauge. The black wire on #6 is ground.

Temp alarm switches are made with a small bimetallic strip inside that bends with change of temp. When the strip is cold the internal contacts are not touching each other but as the strip heats up it begins to bend, and hopefully when it gets to the "alarm temp" it will have bent the correct amount and touch the two contacts together and allow current to flow from the alarm box on the panel thru the switch to ground and cause an alarm condition.

Sometimes the bi metallic strip cracks or comes loose from its attachment point and the contacts can never close, so the alarm will never function, or they can fail where the contacts are always closed and the alarm is always on. Swapping switches from one engine to the other is a good idea to isolate the problem.

DougR

[ShaktisBoy]

Thanks Doug that’s how I thought it worked. I only have idiot lights at the helm which is why I was confused about the single wire from temp switch 4 that goes into a relay box. Since I don’t have a temp gauge at all I thought it might activate the fuel shutoff solenoid but I guess not due to the regulations not allowing a automatic shutdown of a main engine.

[travellerw]

Those sensors are prone to failure on both the D1-30 and the 2030 lines. I have had to replace both of mine.

Parts for Engines has the best price but it may not make sense bringing them from the UK if you are just buying the sensors.

[ShaktisBoy]

Originally Posted by travellerw

Those sensors are prone to failure on both the D1-30 and the 2030 lines. I have had to replace both of mine.

Parts for Engines has the best price but it may not make sense bringing them from the UK if you are just buying the sensors.

Thanks for that