Engine temp alarm on constantly

[Paul&Ness]

Hi Guy's, seeking some help relating to a problem I have with my engine temp alarms connected to Cummins 6BTA 300hp. I have already searched through older posts and nothing found. So my problem is that the Alarm sounds as soon as the ignition is turned on and the engines cold. Both the Alarm buzzer sounds and the warning light is on at the lower helm and upper helm position. Disconnecting the leads from the engine temp sensor doesn't kill the alarm buzzer or the warning light. If I run the engine up to temp the alarm buzzer and light remain on. Put a load on the engine and run for prolonged period and the engine temp gauges show normal operating temps (90ºC)! I haven't been able to find a reset switch to reset the alarm.

Has anyone experience of anything similar?

The boat is a Princess 368 (92) Twin Cummins 6BTA 300's No electronics on the engines.

 

[spannerman]

Have you checked the coolant level in the header tank, Volvo D4/6's do this if the level is too low. You evidently don't have a cooling problem according to the temp gauge, I am not familiar with these engines but would guess its a low coolant alarm. If the coolant level is OK then it will be a wiring fault as it doesn't stop when you disconnect the temp sensor.

 

[david_bagshaw]

Hi

The diagram is too small to be of use to me.

Often there are diodes on the lead to the alarm from each sensor. Perhaps the problem lies here.

 

[Paul&Ness]

Hi Guy's, all levels were checked and have been rechecked so it's not that. As far as I can work out form the wiring diagram there is no coolant level alarm on these engines! I tried everything I could think of too eliminate as much as I could and I am sure that it's a wiring issue. The system is so simple, in as much as there is no computer/ecu, it's got to be something like a short somewhere but where do I start looking?

I can't get the wiring diagram to upload in high enough resolution to beef use...

 

[Neilthesparky]

Hi, can't quite make out the diagram! There is quite often 2 sensors for temp, 1 to show actual temp to a guage and one to trigger a warning light / buzzer/ fan. If it's just on one engine it may be a failed sensor or a short in the wiring. Most temp sensors work on a falling resistance, the warmer the temp the lower the resistance so a short in the wiring would give an alarm as would a sensor that has shorted to ground. If you can identify where the over temp sensor is and disconnect the wire to it and the alarm stops then I'd go for a faulty sensor. Hope that's of use??

 

[superheat6k]

You say this affects both engines is that correct ?

I haven't got that far into the details of my 6BTA5.9M yet, but I would expect there are two temperature sensors - one a sender with analog variable resistance for the gauge, the other a safety switch which closes as the temperature rises for the panel alarm. The oil pressure will have similar alarm and gauge sensors. But for both of these to go defective at the same time seems odd.

Mine do sound at turning on the ignition prior to starting due to the oil pressure being low.

Has any work been done to the engines. Is it possible someone has inadvertently mis connected something, e.g. swapped the gauge and safety switch sensors perhaps..

 

[superheat6k]

This has the B series wiring diagrams listed.

There is only a single sensor sender each for oil and temperature with an electronic module looking at the reading. Possibly a duff module, or possibly a loose connector. I would assume this module resides behind the instrument fascia.

http://www.sbmar.com/cummins-marine-diesel-wiring-diagrams.php

 

[Latestarter1]

Hi Guy's, seeking some help relating to a problem I have with my engine temp alarms connected to Cummins 6BTA 300hp. I have already searched through older posts and nothing found. So my problem is that the Alarm sounds as soon as the ignition is turned on and the engines cold. Both the Alarm buzzer sounds and the warning light is on at the lower helm and upper helm position. Disconnecting the leads from the engine temp sensor doesn't kill the alarm buzzer or the warning light. If I run the engine up to temp the alarm buzzer and light remain on. Put a load on the engine and run for prolonged period and the engine temp gauges show normal operating temps (90ºC)! I haven't been able to find a reset switch to reset the alarm.

Has anyone experience of anything similar?

The boat is a Princess 368 (92) Twin Cummins 6BTA 300's No electronics on the engines.

How long have you owned the boat??

Does this effect both engines?

Take a closer look at your wiring diagram. The alarm is lube oil pressure, in normal operation you key on and alarm sounds, hit the button and as soon as sensor sees pressure alarm is suppressed. key off and as lube pressure drops alarm comes back on.

Do not use the engine until you confirm lube oil pressure is minimum 10 psi hot idle and around 50+ psi at WOT.

Proper troubleshooting steps is to fit pressure gauge to 1/8 NPT spare tapping either on filter head or main oil rifle, if readings are as above check out sensors, alarms generally fail completely, not remain on.

Give me some answers and I can assist you some more.

To answer Trevor's comment re possible loose connection, gauge needle is pinned if bad sensor connection.

 

[Paul&Ness]

Hi... No this only affects the one engine (Port). Everything on the Stb engine operates as it should.

 

[Paul&Ness]

How long have you owned the boat??

Does this effect both engines?

Take a closer look at your wiring diagram. The alarm is lube oil pressure, in normal operation you key on and alarm sounds, hit the button and as soon as sensor sees pressure alarm is suppressed. key off and as lube pressure drops alarm comes back on.

Do not use the engine until you confirm lube oil pressure is minimum 10 psi hot idle and around 50+ psi at WOT.

Proper troubleshooting steps is to fit pressure gauge to 1/8 NPT spare tapping either on filter head or main oil rifle, if readings are as above check out sensors, alarms generally fail completely, not remain on.

Give me some answers and I can assist you some more.

To answer Trevor's comment re possible loose connection, gauge needle is pinned if bad sensor connection.

 

[Paul&Ness]

How long have you owned the boat??

Does this effect both engines?

Take a closer look at your wiring diagram. The alarm is lube oil pressure, in normal operation you key on and alarm sounds, hit the button and as soon as sensor sees pressure alarm is suppressed. key off and as lube pressure drops alarm comes back on.

Do not use the engine until you confirm lube oil pressure is minimum 10 psi hot idle and around 50+ psi at WOT.

Proper troubleshooting steps is to fit pressure gauge to 1/8 NPT spare tapping either on filter head or main oil rifle, if readings are as above check out sensors, alarms generally fail completely, not remain on.

Give me some answers and I can assist you some more.

To answer Trevor's comment re possible loose connection, gauge needle is pinned if bad sensor connection.

Hi Latestarter1.

I have owned the boat for 12 months.
This only affects the Port engine.
The warning lamp that is illuminated is the water temp alarm and the buzzer is attached to that circuit. The buzzer must have been retrofitted at some time in the past!
I filmed the instrument displays the last time we tested which was on Sunday, showing all temps and alarms. I'll send you the video file.

 

[vas]

Hi... No this only affects the one engine (Port). Everything on the Stb engine operates as it should.

check cabling on port oil pressure sender unit?
swap oil pressure senders from stbrd (or just remove the wires from port engine, extend them to reach the stbrd, remove the ones from stbrd, connect them and start both engines up )

 

[Latestarter1]

Hi Guy's, seeking some help relating to a problem I have with my engine temp alarms connected to Cummins 6BTA 300hp. I have already searched through older posts and nothing found. So my problem is that the Alarm sounds as soon as the ignition is turned on and the engines cold. Both the Alarm buzzer sounds and the warning light is on at the lower helm and upper helm position. Disconnecting the leads from the engine temp sensor doesn't kill the alarm buzzer or the warning light. If I run the engine up to temp the alarm buzzer and light remain on. Put a load on the engine and run for prolonged period and the engine temp gauges show normal operating temps (90ºC)! I haven't been able to find a reset switch to reset the alarm.

Has anyone experience of anything similar?

The boat is a Princess 368 (92) Twin Cummins 6BTA 300's No electronics on the engines.

Thank you for the email and I apologise for being dumb, I missed the fact that the overtemp light was on in addition to buzzer sounding.

The Cummins/VDO gauges and all wiring was simply integrated into Princess panels. Spoke with the guy who actually did the wiring integration for Princess. Suggested you ignore temp sensor in head which I suspect is the one you have been pulling leads off. There is a second one hiding in the block, find this big multipin sensor located in the front of the block.

Suggest you switch side for side from stb engine, bit of a faf losing coolant however but these sensors are quite expensive, my man suggests this is your first place to start.

Good hunting

 

[Paul&Ness]

Hi Guy's, thanks for all you replys. I have taken them on board, no pun intended, and will be down on the boat today putting your suggestion into practice. I will update you later today with hopefully a positive outcome...

 

[Latestarter1]

Hi Guy's, thanks for all you replys. I have taken them on board, no pun intended, and will be down on the boat today putting your suggestion into practice. I will update you later today with hopefully a positive outcome...

I did mail you to confirm that I do have a spare secondhand switch.

On revisiting the wiring diagram this sensor is a simple 'Teddington' switch and if you clean layers of old paint off terminals are C=Common, 1 = Make on temperature rise, 2 = Break on temperature rise.

Switches manufactured in U.K and shipped to Cummins in U.S. I have found supplier here who can obtain genuine replacement unit far less expensive than Cummins.

Hope you sorted the problem.

 

[Paul&Ness]

Hi Latestarter1, Think I have solved it! The problem has gone... I spent time at the weekend trying to isolate the problem and during this I changed a couple of the spade terminals that just seemed too loose and the problem is not evident anymore. I am not saying that the spade terminals were the problem but on disconnecting and then connecting etc I must have done something that fixed the problem. Obviously I will be keeping an eye on it closely for a while and will be checking levels etc...

My current system doesn't give me temp/pressure gauges on the flybridge so that a problem area to be as I can't see potential problems arising of I am up top. Does your supplier have dual station sensors/switches for oil/water?

Paul

 

[rogerthebodger]

My current system doesn't give me temp/pressure gauges on the flybridge so that a problem area to be as I can't see potential problems arising of I am up top. Does your supplier have dual station sensors/switches for oil/water?

Paul

You need to look at VDO who do both temperature and oil senders for duel gauges. I have both duel temperature and oil pressure gauges in my cockpit and wheel house.

 

[Paul&Ness]

So the cooling temp a,arm problem is now sorted. Don't know exactly what fixed it but I have no alarms... All temps and pressures are within normal limits. We took Fenland Dancer to Yarmouth yesterday for an overnight to watch the fireworks. Had a steady run down in the morning, monitored the gauges for any fluctuations and all was good. Came back this afternoon and on the final leg up Southampton water I opened her up, again monitoring the T&P's and all was good. I can only think that in the process of tracing the fault and in changing a couple of the spade terminals the fault cleared. I will continue to keep an eye on things over the next few runs.

Thanks to all who contributed. Thats what makes this forum so good; the willingness of fellow boaters and people with greater knowledge happily sharing to help others find a solution

I will look at the VDO senders and gauges as I need these gauges on the flybridge as soon as possible, for peace of mind!

 

[Latestarter1]

So the cooling temp a,arm problem is now sorted. Don't know exactly what fixed it but I have no alarms... All temps and pressures are within normal limits. We took Fenland Dancer to Yarmouth yesterday for an overnight to watch the fireworks. Had a steady run down in the morning, monitored the gauges for any fluctuations and all was good. Came back this afternoon and on the final leg up Southampton water I opened her up, again monitoring the T&P's and all was good. I can only think that in the process of tracing the fault and in changing a couple of the spade terminals the fault cleared. I will continue to keep an eye on things over the next few runs.

Thanks to all who contributed. Thats what makes this forum so good; the willingness of fellow boaters and people with greater knowledge happily sharing to help others find a solution

I will look at the VDO senders and gauges as I need these gauges on the flybridge as soon as possible, for peace of mind!

For single station temperature VDO temp sender p/n 323470 287 Ohms. Dual station p/n 325007 144 Ohms.
VDO oil pressure Cummins p/n 3913627 10 0hms. Dual station p/n 3913616 5 Ohms.

 

[Paul&Ness]

For single station temperature VDO temp sender p/n 323470 287 Ohms. Dual station p/n 325007 144 Ohms.
VDO oil pressure Cummins p/n 3913627 10 0hms. Dual station p/n 3913616 5 Ohms.

Thanks, Latestarter1... Sorry for the delaying responding. I will be making this one of my winter projects

Paul