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Transmission Pressure Alarm or False Alarm

Discussion in 'Post Yacht' started by Soulstice, May 27, 2019.

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  1. Soulstice

    Soulstice Member

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    I know this is better placed on boatdiesel but since I am hoping to get some thoughts, advice, help faster, I thought you guys might be a better place to start.

    So I am bringing the Post home and today we were running a longer day from St. Augustine to Charlestown. About 30 minutes out of the channel, the MAN alarm starts going off for Gearbox Oil Pressure (clutch). We bring the boat down to neutral, check the transmission and everything looks good (apart from a hot as hell day and hotter engine room). We let everything cool down for a while thinking it may be due to the heat and a long run today. The alarm still went off anytime we got over 1,200 RPM although the analog pressure gauge is showing the same pressure for both transmissions (350-375).

    There is no slipping, the gear shifts normally, the oil is clear and amber (Changed about 30 hours ago with a recent analysis looking good), and the fill level when warm is the same for both transmissions.

    After letting the engine room cool down a few hours, we looked it over. On this boat there is a regular analog transmission pressure gauge and then this MAN sensor panel. On the transmission itself, it appears there is one sensor on the gear (analog pressure?) and one on the heat exchanger (transducer?). We found that a wire on the sensor mounted on top of the heat exchanger had broken off.

    We have now repaired this and are preparing a ~200 mile run in the morning but I am looking for advice on whether this is most likely the source of the alarm or what else could be setting off that alarm on the MAN display? What is the source of this alarm for the MAN display, is it the sensor on the heat exchanger? Are these the sensors that tend to go bad? My gut tells me the transmission is fine based on the analog gauge but I would to hear if anyone else has had this issue or can provide us advice before we leave tomorrow to test it out.

    Thanks for any help you can provide.

    Jay
  2. Capt Ralph

    Capt Ralph Senior Member

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    MAN engines and peripherals have DanFoss senders. These senders are famous for false alarms.
    Please review past MAN threads.
    If you have mechanical gauges and during your speed runs they look good, can the alarm and keep running.
  3. Seth Fisher

    Seth Fisher Member

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    I had similar issues on my ZF and MTU, replaced the sender and all is good. The new senders read more accurately than the old ones...
  4. Soulstice

    Soulstice Member

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    So here is the update. The wire that had broken off the sensor on top of the transmission cooler was the culprit. This attaches two sensors (one on the gear and one on the cooler) to the MAN alarm system. I re-stripped the wire and attached it to the sensor and we ran all day today with no issues.
  5. Soulstice

    Soulstice Member

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    Just as a follow-up to this topic and so I don’t create a separate thread, I had another one of these wires break Off the terminal from fretting and am going to look at replacing the sensor.

    Does anyone with a 50 Post with Man’s know who makes this sensor? I can’t find a part code in any of my books and it is worn off the sensor which is located on the heat exchanger for the transmission gear oil. This is what triggers the Man alarm for gear temp. I will also reach out to Bayside Diesel but I wanted to ask if anyone knew off their head.

    Attached Files:

  6. Capt Ralph

    Capt Ralph Senior Member

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    Dan Foss makes the senders. You will never be able to cross it.
    Call Performance Diesel in Houston with your serial number. Out in today's mail.
  7. Soulstice

    Soulstice Member

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    Thank You! I will call the guys at Performance Diesel as they are always a huge help.
  8. Capt Ralph

    Capt Ralph Senior Member

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    Because of the lack of MAN support in the Jax area, I copied their phone number from a decal on a V8-900 CRM in a SeaRay.
    Talking about support. They sent manuals and spent some serious time in detailed phone support. All my part orders no matter how large or small came thru there from then on.
    I have bragged on these kids before.
  9. Soulstice

    Soulstice Member

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    Just wanted to close out this topic as I have finally found the replacement sensors thanks to Performance Diesel. It turns out they setup all the MAN packages for Post back in the day and certainly for my 2000.

    The part in question is a temperature alarm switch, part number TM-2C-203R/20. They go for around $85 as of March 2021.
  10. Capt Ralph

    Capt Ralph Senior Member

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    In your hands for less than $100. Probably the cheapest sensor on the engine package.
  11. Capt Fred

    Capt Fred Senior Member

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    If you loosen the wire and use a tie wrap to secure the wire to the sensor you will improve the reliability of that connection. In the picture that wire appears taught and will vibrate and break. The tie warp take the strain off the bare copper wire at the connection. It's a good idea to do this on every connection on the engines.
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  12. Capt Ralph

    Capt Ralph Senior Member

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    This is a great idea.
    I have always tried to cable tie wires down to the engine or on wire runners. Also try to have a single & flexible harness umbilical to the boat.
    I do get carried aweigh on shrink crimps, shrink tubing pairing, chafe protecting wires and sealing wire ends also.
    It's so automatic, I forget to mention these little things.
    436055_TMB.14112018103253.jpg
    Capt Fred likes this.