The famous random overtemp alarm for no reason

[mstotler8]

If youre getting the random alarm for no reason, all guages good etc etc, its in the ICM, you can replace it for half a grand, throw money at stats, impellers, sensors or...

First I verified its definitely initiated in the temp warning alarm circuit, I pulled the yellow wire out of connector at ICM and other end at temp sensor, good continuity(under 3 ohms) while pulling and shaking the s%i* out of the harness, never blinks. If I ground the yellow wire to t-stat housing (proved grounded, again under 3 ohms resistance) repeatedly I get the alarm maybe 1 out of 5 times, also alarm most time wont stop even after pulling the ground, just keeps on buzzing until I pull the tan/blue wire from other ICM connector to remove continuity to buzzer. Ah hah, its the relay (or whatever) in the ICM.

What I did is pull the yellow terminal out of ICM connector and tan/blue from other ICM connector and splice them together. Now alarm system functions as should. If I heat temp sensor to just under boiling (inexactly 190 degrees) it closes and sends ground to buzzer as designed (just not through ICM). IR thermometer says engine is running at 168 degrees, Now take all that money you were going to spend on t-stats, impellers, hoses, water pumps, sensors and put it in the gas tank.

The only thing Im not sure of is if ICM still retards/advances timing as designed even if relay thinks its sending ground to the alarm. Doesnt seem to affect the performance of my 5.0 at all, except peace from the alarm and peace of mind that nothing is wrong with my engine. Id love to get ahold of an ICM and open it up to further research. If anybody has a junk one laying around and would like to donate to science LMK.

Some of us with carbed engines have this frankenstein wire harness that has a yellow and black 2 wire temp sensor for the alarm, part MIE and part MCM, I believe when they were transitioning from carb to FI we got these "in between" builds while they used up stock or had afterthoughts at the factory and ours dont match any diagrams to a T. I believe the ICM is also in between designs and thats where our problems begin.

 

[QBhoy]

Sounds like you’ve had a bit of trouble with this...but please forgive me for noticing that you might not have considered that the alarm may be from the gear oil header tank ?

 

[achris]

Hello mstotler8 , and :welcome: aboard...

Can we ask, what engine are you playing with?

As for an 'in between' harness. I have never heard of that. The harness for the carbed engines is the same as Merc have been using since the 70's.

If by 'ICM' you're referring to a Thunderbolt V module, again, not an afterthought, a generational improvement of the extremely successful and very reliable Thunderbolt IV, which came to us in 1984. And this 'famous' beeping alarm problem, you're the first I have heard with it, and I was a Mercruiser dealer when TB-V was new, and we never saw any problems with them, except when people tried to mess with them. You may have a faulty one, that's not impossible, but it's not common.

Chris.......

 

[mstotler8]

I respect you maybe had a dealership, you are wrong.

facts are the “generational improvement of the extremely successful and very reliable Thunderbolt IV module“ ( I won’t dare call it a ICM) is opening the ground to the alarm at ambient temp with ZERO input from the 2 wire temp sensor (yellow n black)in the T stat housing. “Playing with” you had to go there.

Fun Times looks to also be a well respected member of this forum, guess he plays with stuff too.

read up a little if you care if not whatev,

https://forums.iboats.com/forum/eng...ser-4-3-tks-intermittent-false-overheat-alarm

 

[mstotler8]

Sounds like you’ve had a bit of trouble with this...but please forgive me for noticing that you might not have considered that the alarm may be from the gear oil header tank ?

Uhmm... yea. Thanks for reaching out anyways. Maybe its the way i explained it? Im leaving post up, hopefully it helps 1 person someday. Thats all I was after.

 

[GA_Boater]

I respect you maybe had a dealership, you are wrong.

facts are the “generational improvement of the extremely successful and very reliable Thunderbolt IV module“ ( I won’t dare call it a ICM) is opening the ground to the alarm at ambient temp with ZERO input from the 2 wire temp sensor (yellow n black)in the T stat housing. “Playing with” you had to go there.

Fun Times looks to also be a well respected member of this forum, guess he plays with stuff too.

read up a little if you care if not whatev,

https://forums.iboats.com/forum/engi...overheat-alarm

Too bad you didn't read and understand Fun Times post. He said;

Thus far the unofficial fix has seemed to of been inspecting, disconnecting, cleaning, gently wiggling/pushing in the wire pins at the ICM connectors to ensure the associated wires/connectors are seated/making proper contact to the ICM.

Did you try that? Many replies after his post said doing what he recommended cured the random alarm.

Also just because you disagree with someone doesn't make you right. Remember that respect is a two way street and you may be coming back to ask for help when your work around causes a $5000 mistake.

 

[mstotler8]

Too bad you didn't read and understand Fun Times post. He said;



Did you try that? Many replies after his post said doing what he recommended cured the random alarm.

Also just because you disagree with someone doesn't make you right. Remember that respect is a two way street and you may be coming back to ask for help when your work around causes a $5000 mistake.

glad you said that because I’ve disrespected nobody. I got told I was basically a child playing with things, only to be followed up with 3 absolutely wrong statements from a pompous ex mercury dealer I was just trying to help someone and add something to an apparently non-existent problem that literally hundreds of people seem to have at one time or another. . Never mind I’ll take it down, geez sorry.

as far as the 5k mistake, that’s another point I can’t let go. I’ve tested it with a Pyrex bowl of water, an IR temp reader and a sterno can. All 3 times the alarm sounded at around 190 degrees, I know it works. Would you bet 5k that that alarm will sound after the “jiggle fix”? Think about what you’re saying. You trust a “generational improvement of the extremely successful and very reliable Thunderbolt IV module“ ( Do not call it the ICM) that needs jiggle fixed over a proven, tested reliable circuit ? Honestly it was the “playing with” statement that I even fell into this rabbit hole. He knows nothing about me, my electronic background or what I do for a living on a daily basis.

If I have in any way disrespected or offended anyone please know that was never my intent save for 1 pompous ex mercury dealer. This all really started with trying to save even one person some money, time and heartache.

 

[mstotler8]

Rough crowd in here.
Please at least tell me you see what I’m saying?? Do you know that alarm will work?? I grounded that yellow wire 50 times, got an alarm maybe 10. I just don’t trust that over mine, right, wrong or indifferent.

unplugging, juggling the connector, in other words applying power and ground repeatedly in other words “resetting the module” presto... fixed, no more alarm.

Exactly

look I get it it’s not “the fix” we won’t all put a 500 module in a 10 k boat when we have giauges, IR thermos and basic mech/elec knowledge. I thought the point of y’all’s forum was to save the average joe boater some money time and heartache, make it more affordable and enjoyable. No, you’re a child playing with things you shouldn’t.

 

[metsfan3197843]

FYI asking someone what they are "playing with" is an extremely common phase on the forum when someone doesn't post what exactly they are working on. I highly doubt it was a shot at you or worth getting so riled up about.

 

[GA_Boater]

Now we have a pompous ex-Merc dealer. Right after you say you didn't disrespect anyone. :facepalm:

I gotta ask - Who's the pompous one?

You came in here waving flags with a marching band saying you had the answer with your very first post. You have no reputation in this forum, so you got what happens when a new member says "Hey, look what I found" with no basis of what could be considered to be normal troubleshooting.

And it's obvious you still haven't read or understood what Fun Times wrote. It isn't a jiggle fix. FT's fix is free and only takes some time by the boat owner. You spent more time with all your 50 groundings of the wire, rewiring and sticking the sensor in hot water.

You're happy playing with your toy. Good for you.

Go ahead and take it down. :lol:

 

[mstotler8]

Now we have a pompous ex-Merc dealer. Right after you say you didn't disrespect anyone. :facepalm:

I gotta ask - Who's the pompous one?

You came in here waving flags with a marching band saying you had the answer with your very first post. You have no reputation in this forum, so you got what happens when a new member says "Hey, look what I found" with no basis of what could be considered to be normal troubleshooting.

And it's obvious you still haven't read or understood what Fun Times wrote. It isn't a jiggle fix. FT's fix is free and only takes some time by the boat owner. You spent more time with all your 50 groundings of the wire, rewiring and sticking the sensor in hot water.

You're happy playing with your toy. Good for you.

Go ahead and take it down. :lol:

wow, you really told me... everything but where Im wrong?

:baby: "you called my friend what he was acting like":baby: doesnt prove anything. Reputation and facts are 2 different things, If a reputation makes wrong statements correct in your little world then have it. Im good, my boats good, I dont know why I care so much. I can see all you guys as 6th graders taking a 2nd graders lunch money then standing around high fiving each other like ' We're so bad ass" Thought Id give something back due to once a few years ago I came across a basically free boat with OMC. Ive been around Mercury since I could walk but wasnt at all familiar with these and I learned a LOT from a very intelligent guy on here named Don S. Whatever.

 

[GA_Boater]

You said your piece.

Closed.