TKS Ignition system hissing/sucking - not working properly

[IS-217]

You mean jump the diode plug don’t you. Lol I feel stupid now…
Why am I removing the fuse btw? Lol I almost understand this system… stay with me.
Here’s a pic of the 15Amp fuse behind engine. Pink wire & red wire with purple stripe.

 

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You mean jump the diode plug don’t you. Lol I feel stupid now…
Why am I removing the fuse btw? Lol I almost understand this system… stay with me.
Here’s a pic of the 15Amp fuse behind engine. Pink wire & red wire with purple stripe.

If that 15 amp fuse continuous to blow, look for a cut open chafed wire including all the wiring at the alternator and not rubbing on something or even the damaged wire you mentioned may had been rubbing on a sharp edge. This member ended up blowing both fuses at different episodes.

Blowing Fuses

There has to be more then 2 wires. 1-supplies battery voltage 2-supplies voltage to run system (when key is turned ON) 3-supplies power to start relay to crank the motor over

forums.iboats.com

Some say the engine will run while others say it won't run... some don't get 12 volts on the purple and it seems to depend on how the diode is working correctly or not for how the engine/12v system works at the time of failure... So keep that in mind as you're testing and changing things out. Also I recommend you always keep an extra diode onboard in case it fails again while out.

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[alldodge]

Yes use a short piece of wire to replace the diode. Doing this will send 12V to TKS when key is on. With power applied the hissing should stop and if it does then we will know it's ok

The fuse is remove to find out if the diode path works or not. If it does work then the temp switch is not making a connection even when motor is warmed up. Removing the fuse also allows the motor to be turned Off. As shown on previous pic, if the diode shorts out (we are jumping it) the motor could not be shut off

After the above test, could try one more test with motor warned up. To verify if the temp switch is working replace the fuse and start the motor. Turn key off and the motor should keep running. If it does keep running the the temp switch is closed, if it doesn't then it's open

 

[IS-217]

If that 15 amp fuse continuous to blow, look for a cut open chafed wire including all the wiring at the alternator and not rubbing on something or even the damaged wire you mentioned may had been rubbing on a sharp edge. This member ended up blowing both fuses at different episodes.

Blowing Fuses

There has to be more then 2 wires. 1-supplies battery voltage 2-supplies voltage to run system (when key is turned ON) 3-supplies power to start relay to crank the motor over

forums.iboats.com

Some say the engine will run while others say it won't run... some don't get 12 volts on the purple and it seems to depend on how the diode is working correctly or not for how the engine/12v system works at the time of failure... So keep that in mind as you're testing and changing things out. Also I recommend you always keep an extra diode onboard in case it fails again while out.

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www.mercruiserparts.com

Sorry FT you lost me.
I haven’t mentioned any damaged wires.
I uploaded a pic of the 15Amp fuse that is blown. It has a pink wire and a red wire with purple stripe. Where do these wires come from relate to? Alternator? Previous owner had the starter replaced. Would the starter be part of the problem.

 

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The diode is no good no continuity both ways looks like it shorted out one pin is grey/burnt looking.

Was going off of this comment in the first post.
Without an updated wiring diagram, I'm unsure of the pink wires routing...I just know of the fuse and wire but unsure of the exact specifics that it handles. It seems some have reported issues with the temp switch wires rubbing and others didn't blow that one but the 20 amp closer to the diode / carb area.

 

[IS-217]

Was going off of this comment in the first post.
Without an updated wiring diagram, I'm unsure of the pink wires routing...I just know of the fuse and wire but unsure of the exact specifics that it handles. It seems some have reported issues with the temp switch wires rubbing and others didn't blow that one but the 20 amp closer to the diode / carb area.

Hey FT, yes I realize now my wording was wrong for the diode, alldodge said the same thing, all I knew was that it had no continuity both ways as stated in the post which means open. I just said shorted because it looked burnt inside. Can I edit that post now I can't find a way to do so. Would be good to do for other viewers following along.

As for the 15amp fuse. Should I just replace and see if it trips again. I'll be running the boat tomorrow. I'm getting a new thermostat, and a new diode from electronics store. I'll see if engine warms up to 160 and then hopefully temp switch closes and TKS system starts working properly again. I guess I'll see if the 15amp fuse trips again when I hook everything up.
Did I miss anything? Is it worth doing the diode jumper test? I may as well change the thermostat if its not getting up to temp anyways and the diodes are cheap from the electronic store.
One more thing. If all is good after changing to new parts do I need to seal up the new diode to prevent shorting (bare metal will be exposed).

We'll know after tomorrow. Wish me luck guys. Thanks for all your help. You guys really know your stuff this forum is great. Hope this is the fix.
Cheers

 

[IS-217]

Yes use a short piece of wire to replace the diode. Doing this will send 12V to TKS when key is on. With power applied the hissing should stop and if it does then we will know it's ok

The fuse is remove to find out if the diode path works or not. If it does work then the temp switch is not making a connection even when motor is warmed up. Removing the fuse also allows the motor to be turned Off. As shown on previous pic, if the diode shorts out (we are jumping it) the motor could not be shut off

After the above test, could try one more test with motor warned up. To verify if the temp switch is working replace the fuse and start the motor. Turn key off and the motor should keep running. If it does keep running the the temp switch is closed, if it doesn't then it's open

Hey alldodge,
Do we know if temp switch is bad if thermostat not working (engine too cold) does your test work if thermostat still no good or is this test based on thermostat getting engine up to 160.
See my last post to FT.

 

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At this point I’d say put everything you have/can in new, double check all wires everywhere you can for cut open type damage and/or rubbing on something then go test the boat to see what happens before going much further…. Have extra fuses on board in case they blow later to Tty to get back home.

No real need to go back and edit the thought to be damaged wire, it worked itself out.

 

[IS-217]

At this point I’d say put everything you have/can in new, double check all wires everywhere you can for cut open type damage and/or rubbing on something then go test the boat to see what happens before going much further…. Have extra fuses on board in case they blow later to Tty to get back home.

No real need to go back and edit the thought to be damaged wire, it worked itself out.

I'll be doing the work and running the boat on the driveway.
Time to put her to sleep for the winter.....
This is my only weekend I have before life gets too busy and the days get too cold. Any issues doing all this on the muffs?

 

[IS-217]

Update.
After replacing the thermostat and wiring up the new diode the TKS system is running good again no more hissing noise after warmed up for 10mins or so.
Very happy the issue has been resolved.
Thanks again guys. You guys have been very helpful.
Now I just need to figure out the 15Amp fuse on the back of the engine.
I bought some fuses only to find out the fuses I bought were too big. This 15Amp fuse is smaller. Does anyone have a suggestion where I can buy the proper fuses. I didn’t see any other sizes where I bought them and they need to be marine application (sealed up bottom side) I also learned that auto and marine fuses are different auto fuses are open bottom side between the pins whereas marine fuses are sealed.
Cheers

 

[alldodge]

Thanks for the update
Search for "mini blade fuse"

 

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www.mercruiserparts.com

15	832969T15	FUSE, Mini - Blue - 15 Ampere	83296915	SS/ACT		$3.90	$3.81	1
15	832969T20	FUSE, Mini - Yellow - 20 Ampere	83296920	SS/ACT		$6.30	$6.15	1

 

[IS-217]

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www.mercruiserparts.com

15	832969T15	FUSE, Mini - Blue - 15 Ampere	83296915	SS/ACT		$3.90	$3.81	1
15	832969T20	FUSE, Mini - Yellow - 20 Ampere	83296920	SS/ACT		$6.30	$6.15	1

Hey FT thanks for the link.
Do you know if these fuses are sealed on the bottom?
Does it matter if they're open or closed I haven't been able to source mini blade fuses that are closed on the bottom between pins. Do they need to be sealed if inside the waterproof fuse holder?
Thanks

 

[Fun Times]

Hey FT thanks for the link.
Do you know if these fuses are sealed on the bottom?
Does it matter if they're open or closed I haven't been able to source mini blade fuses that are closed on the bottom between pins. Do they need to be sealed if inside the waterproof fuse holder?
Thanks

It's still preferred to be sealed even if encased in a waterproof holder anything other than that is much like using what engine oil, oil filter and ways of winterizing an engine, it becomes a matter of opinion vs facts and who's watching and/or paying in the end.... < In my opinion of course.

That is Mercruiser's part number so yes it ought to be sealed, https://www.ebay.com/sch/i.html?_from=R40&_trksid=p4432023.m570.l1313&_nkw=832969T15&_sacat=0

ATO vs ATC fuses in bilge

Have a fuse holder in bilge that’s always hot for bilge pump. It’s factory installed blade fuse holder with the weatherpack-like gasket. Do I need to use an ATC to prevent a spark hazard? I ordered a 25 pk of ATC’s but received ATO’s and would like to use.

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