Merc 600 SCI IAC 1 Amp Fuse Install
01-14-2017 | 11:19 AM
#12
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Joined: Dec 2007
Posts: 174
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From: Cary, IL
I recommend installing the fuse even if you are replacing the IAC every season. I do not believe it has anything to do with being gummed up since I have had perfectly clean ones fail and the pintles were never stuck. Plus, the IAC is a stepper motor and the current draw is independent of load so it wouldn't matter anyway.
GF?
GF?
01-14-2017 | 02:59 PM
#13
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Joined: Jun 2005
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From: River Falls WI
Ive repaired 2 ecm drivers on 2 different 700 boats, so after the 2nd one i learned a lot about this problem after talking to a couple of, what i think are a good source, marine mechanics and one said fuse both wires the other said for sure the negative and wouldn't hurt to do the positive so i did both. I looked up a wire schematic for my motor based off serial # just to see how that circuit is wired and you can figure out which wire is the negative if you choose to do only the negative
01-17-2017 | 08:19 AM
#14
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From: minnesota
There are two wires connected to the IAC and I don't recall the colors but you can figure out which one to put the fuse on fairly easily. The PCM controls the ground to the IAC and the other wire will have 12 volts with the ignition turned on. The 12 volt wire is connected to a 20 amp fuse that powers the boost controller and the IAC, which you can find in a fuse holder mounted on the plate near the PCM. Use a voltmeter/test light to figure out which one has 12 volts and that is the one you want to have the fuse installed on. I recommend unplugging the two connectors to the PCM whenever you are testing circuits, just in case.
Worst case, you can just put a fuse on both wires and it will be fine.
GF?
Worst case, you can just put a fuse on both wires and it will be fine.
GF?
01-17-2017 | 11:17 AM
#16
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Joined: Dec 2007
Posts: 174
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From: Cary, IL
Correct, you need a 1 amp fuse to properly protect the PCM. I installed the inline fuses on my 700SCi's eight years ago and they have protected my computers many times.
03-16-2017 | 08:07 PM
#18
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Joined: Jun 2011
Posts: 2,169
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From: Henderson, KY
Hey, GF?, I've been looking at the wiring diagram tonight. The PCM controls the ground for the IAC (as well as other controls). The 12v source is shared with the boost controller. This 12v source is supplied through the fuse from the Main Power Relay. I don't see how a 1A fuse on the 12v source is going to to protect the PCM, as they are not connected. A high amperage situation on the negative side of the IAC could result in damage to the PCM.
Would you further explain your logic. I appreciate it!
Terry
Would you further explain your logic. I appreciate it!
Terry
There are two wires connected to the IAC and I don't recall the colors but you can figure out which one to put the fuse on fairly easily. The PCM controls the ground to the IAC and the other wire will have 12 volts with the ignition turned on. The 12 volt wire is connected to a 20 amp fuse that powers the boost controller and the IAC, which you can find in a fuse holder mounted on the plate near the PCM. Use a voltmeter/test light to figure out which one has 12 volts and that is the one you want to have the fuse installed on. I recommend unplugging the two connectors to the PCM whenever you are testing circuits, just in case.
Worst case, you can just put a fuse on both wires and it will be fine.
GF?
Worst case, you can just put a fuse on both wires and it will be fine.
GF?
03-17-2017 | 08:01 AM
#19
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Joined: Jun 2010
Posts: 392
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From: Birmingham, AL
There are two wires on the IAC. For all practical purposes, power into the IAC will equal power out. It does not matter which wire the fuse is installed on, current flow will be the same in both.
Although I have never had an IAC failure on our 496, I did replace it last year just because. I do like the idea of the 1 amp fuse however and will put this in.
For whoever asked, the IAC is located on the rear of the intake manifold.
[ATTACH=CONFIG]565655[/ATTACH]
[ATTACH=CONFIG]565656[/ATTACH]
Although I have never had an IAC failure on our 496, I did replace it last year just because. I do like the idea of the 1 amp fuse however and will put this in.
For whoever asked, the IAC is located on the rear of the intake manifold.
[ATTACH=CONFIG]565655[/ATTACH]
[ATTACH=CONFIG]565656[/ATTACH]
