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  1. #1

    Default Alarm Wiring Question

    I have a 1995 Rinker Flotilla with 4.3L Mercrusier engine.

    Just pulled the boat out from winter storage and now I now have an alarm with the Key ON. I don't recall exactly the Key On scenario last Fall, but I know it ran correctly without the alarm. I've done a handful of maintenance over the winter such as replacing lower unit impeller, oil + filter, gear lube, and installed a handful of electronics like fish finder, stereo, and Automatic Low Voltage Disconnect.

    I've read dozens of posts on this and have now purchased the wiring diagram. According to the diagram, only the Water Temperature, Drive Unit Oil, and Oil Pressure Switch can/should trigger the alarm. They are wired together in a OR-configuration so that if any of them short to ground the alarm activates. Well... I disconnect all 3 and my alarm still activates!

    I next disconnected the main wire harness plug in the engine bay and confirm the short to ground was in the engine bay. I'm not sure how this happened. I don't see any obvious damage from mice/rats. The wire harness is still wrapped in tape.

    Any ideas where I go from here? My best idea is to instead of tearing apart the entire harness is to cut the tan/blue wire and then use new wire to re-wire each sensor back to the plug.

  2. #2
    Join Date
    Jul 2008
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    Northboro, Ma, USA
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    Default Re: Alarm Wiring Question

    """""I've done a handful of maintenance over the winter such as replacing lower unit impeller, oil + filter, gear lube, and installed a handful of electronics like fish finder, stereo, and Automatic Low Voltage Disconnect.""""



    Based on all the posts you have going for all these electrical related problems I would UNDO everything you did over the winter and see if all returns to normal.

    WTF is a automatic low voltage disconnect?
    Jack
    Mass.

  3. #3

    Default Re: Alarm Wiring Question

    kghost, Thanks for all your replies. I'll have more time to continue troubleshooting hopefully tomorrow evening and will report back more findings.

    The Low Voltage Disconnect is a circuit that takes battery power away from everything when voltage drops below a setpoint. It is a product marketed for Marine applications. I bought it on Amazon. It is called "Blue Sea Systems m-LVD Low Voltage Disconnect" I just wired it to the non-mission-critical electronics (basically everything but the starter and trim).
    I wanted this because I've had too many accidental moments of forgetting to turn off a light, radio, etc... and coming back to a boat with a dead battery that no longer holds a charge.

    Yes, I agree that these changes seem very suspect since it worked before and now I have several issues, but I'm really scratching my head to figure out why this would cause these types of problems.

  4. #4

    Default Re: Alarm Wiring Question

    I did have another measurement last night that was really bothering me, but I didn't know what to make of it. I was at the instrument cluster and measured resistance between power and ground (with the Key ON). I measured between 5-15 ohms depending on where I measured. Is that normal or a symptom of a larger problem?

  5. #5
    Join Date
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    Default Re: Alarm Wiring Question

    Quote Originally Posted by ignisuti View Post
    I did have another measurement last night that was really bothering me, but I didn't know what to make of it. I was at the instrument cluster and measured resistance between power and ground (with the Key ON). I measured between 5-15 ohms depending on where I measured. Is that normal or a symptom of a larger problem?


    I think you are doing and over thinking.....too much..

    You CANNOT do resistance when power is applied..............Dump the volt meter and get a 12 volt test light.

    With a simple electrical system as with this year boat, all you need to look for is a strong 12 volt light when connected to a test point.

    Alligator goes to ground and pin point of tester goes to test point. Bright light and you have 12 volts. Can be used in reverse to see if you have a good ground also.

    Problem with a meter is, it shows volts which may be present but you have no idea of amps/current flow. A test light shows this by way of brightness. Dim means issues bright means good voltage/current
    Jack
    Mass.

  6. #6
    Join Date
    Jun 2008
    Location
    Island Heights, NJ,
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    3,622

    Default Re: Alarm Wiring Question

    FWIW.... on all my boats 18 ft and larger, I've installed 2 batteries.... The main "start" duty battery ( one size bigger than min recommended by engine manufacturer) and a second "dual purpose" battery. The "dual purpose" battery runs ALL my electronics plus the 500 gph "rain water" (non automatic but with separate "caged" float switch for auto function"bilge) pump in my boat.
    The "start" battery only powers the engine plus nav lights pus the 2000gph "holy s$%t" bilge pump..... also with a caged switch.
    A 1-2-off-both switch controls it all.... I run out on 1 battery and home on the other. NEVER run on BOTH to attempt to charge both batteries.... it degrades battery life. Recently I installed a single output marine grade charger which is connected to the dual purpose battery... While my boat was in the water about a mile from Sandy's ground zero path and all worked as planned ( the 2000 gph took over after the dual purpose battery went dead), I decided that the roughly $100 was worth it to keep the dual purpose topped up as long as possible in the event of another "sandy like" rain event.

    Re: "My best idea is to instead of tearing apart the entire harness is to cut the tan/blue wire and then use new wire to re-wire
    each sensor back to the plug."

    Turning the 1-2-both-off switch to "off" when you leave the boat will leave the only thing that should have power, "hot", i.e. the bilge pump.... if your boat is wired correctly.

    NOT a good idea....likely to make more problems than it will solve. Follow KGHOST's advice.

    Unless you ran a separate fused heavy 2 conductor wire from your battery to your electronics you will have problems... wiring electronics to the dashboard circuit often results in "issues". The wiring to the dashboard is not intended to supply power to a number of accessories.
    Last edited by sandkicker; 05-29-2021 at 11:14 AM.
    Capt Bob
    1969 23ft ChrisCraft Lancer
    Merc 5.7L 260HP/ Volvo 280

  7. #7

    Default Re: Alarm Wiring Question

    Well, I found the alarm trigger!
    I found another tan/blue wire that I didn't know about on the back side of the engine just below the distributor on the port side. I runs to what looks like a temperature sensor mounted on the block. Pulling and removing this push-on connector stopped and re-triggered the alarm.

    So, hopefully you guys can help me understand what this sensor is so I can order it. I thought the temperature sensor/sender was on the thermostat housing...? Are there a total of 3 senders/switches? It looks like it is maybe part #48952, but I would like someone to help me confirm as it's roughly $100 for this switch.

    Jack, regarding the resistance test with power applied, you're 100% right. I should know that!!! I was in a rush combined with lack of sleep!

  8. #8
    Join Date
    Sep 2010
    Location
    Jersey Shore
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    6,250

    Default Re: Alarm Wiring Question

    That is the low oil pressure alarm switch. It opens shutting off the alarm when the oil pressure comes up.
    Chris
    Dockside Marine Services
    Jersey Shore.
    Mercruiser/Mercury Certified
    Let the insanity begin.

  9. #9

    Default Re: Alarm Wiring Question

    Quote Originally Posted by Docksidemarineservices View Post
    That is the low oil pressure alarm switch. It opens shutting off the alarm when the oil pressure comes up.
    not from the part # he is quoting

  10. #10

    Default Re: Alarm Wiring Question

    it looks to me that you are having multiple wiring problems and they should all be looked at possibly having a common root cause.
    the alarm for the high temp runs through the thunderbollt module, yellow wire to module wich comes out of the module in the tan/blue wire. remove the tan/blue from the module and run the engine, see if the alarm is still sounding.

  11. #11
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    Default Re: Alarm Wiring Question

    There's no high temp alarm on these older MEFI engines. If there were, then there would be far fewer overheating posts ha ha. The sensor with the yellow wire is a temp sensor but that's just for the ECU's info and not for alarms or anything. In 1995 he would have MEFI 1 or 2 I think.
    The only alarm is low oil and those have the tan/blue that the OP is asking about.
    OP, be sure all your grounds are clean and tight. You might have a bad low oil pressure sensor. Those are about $10.
    To be clear, the alarm sensor is just that, an alarm trigger. It will not shut off the engine if oil pressure is lost. It only sounds the alarm (if it is working). You should have a (working) oil pressure gauge on your dash and if you don't you should.
    Last edited by o2batsea; 05-31-2021 at 09:14 AM.
    Practicing the ancient art of ren-ching

  12. #12
    Join Date
    May 2010
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    Default Re: Alarm Wiring Question

    Slightly off-topic, you should consider adding a second battery as suggested, and then use a voltage sensing relay and emergency parallel switch. What this does is isolate the start and accessory batteries so that the start battery never gets discharged. The voltage sensing relay will bleed off extra voltage to the accessory battery after the start battery is full, so that both batteries get charged. In case the start battery cannot start the engine, the emergency parallel switch will connect the accessory battery to the engine allowing the engine to start.
    This eliminates a 1,2, BOTH, OFF switch.
    Your accessory battery (bank2) should be a big fat group 34 deep cycle marine. Your start battery can be smaller like group 27 but dual purpose type. This should allow you to party all night and still fire the engine.
    Practicing the ancient art of ren-ching

  13. #13

    Default Re: Alarm Wiring Question

    Quote Originally Posted by stang32 View Post
    not from the part # he is quoting
    stang32, that was mainly a wild guess. The diagrams I looked this up from were not very helpful as it just showed me a list of sensors and not the location on the engine.

    o2batsea, Thanks for all the info. That sounds like a something I really want to setup. Do you have a good link that gives a bit more details with a wiring diagram? Currently, I have 2 batteries, but they are both wired in parallel. No 1,2, off, switch.

  14. #14

    Default Re: Alarm Wiring Question

    Can someone please help me with the part number for this oil sensor? Can't see to find it on the parts diagram.

  15. #15
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    Default Re: Alarm Wiring Question

    Jack
    Mass.

  16. #16
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    DC Burbs/Maryland Eastern Shore
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    Default Re: Alarm Wiring Question

    Quote Originally Posted by ignisuti View Post
    Do you have a good link that gives a bit more details with a wiring diagram? Currently, I have 2 batteries, but they are both wired in parallel. No 1,2, off, switch.
    I use a Yandina Combiner 100. You just install it according to their instructions and it does all you need it to do without you having to think about it. Has voltage management and emergency combiner in one small package. I love mine, and it just works. Currently $70. https://www.yandina.com/c100Info.htm
    There are plenty of others out there. Blue Sea Systems seems to be the one that Google points to all the time whether that's cz they pay for that or what I dunno, but that's another possibility.
    Practicing the ancient art of ren-ching

  17. #17

    Default Re: Alarm Wiring Question

    Quote Originally Posted by o2batsea View Post
    I use a Yandina Combiner 100. You just install it according to their instructions and it does all you need it to do without you having to think about it. Has voltage management and emergency combiner in one small package. I love mine, and it just works. Currently $70. https://www.yandina.com/c100Info.htm
    There are plenty of others out there. Blue Sea Systems seems to be the one that Google points to all the time whether that's cz they pay for that or what I dunno, but that's another possibility.
    That sounds like a really cool setup. I'm putting this on my To-Do list.

    Thanks everyone! I'm ordering my oil switch. That should fix this issue!

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