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Merc 600 SCI IAC 1 Amp Fuse Install

Old 01-11-2017, 10:47 AM
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Default Merc 600 SCI IAC 1 Amp Fuse Install

I want to install the in-line 1 amp fuse to prevent IAC failure damage to the computer. Threads talk about it but no real specifics. Can Someone take a minute and post info on what wire to install this on and any photos would be appreciated, Thank you!!
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Old 01-13-2017, 11:51 AM
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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?
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Old 01-13-2017, 12:05 PM
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Red with blue & white with blue , I would like to do this also I went through the ECM burn last year .
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Old 01-13-2017, 12:56 PM
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Thank you both for posting will dig into this and post back.
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Old 01-13-2017, 04:55 PM
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Is it Fountain problem? I've seen a bunch go out of them, sometimes taking the ECM with it.
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Old 01-13-2017, 05:05 PM
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Not specific to Fountain, all 600/700sci's are prone.

Had an IAC failure second season after getting boat, knew from reading to kill ignition power immediately to save ECM. Been replacing IAC's every other year now, cheap insurance to eliminate failures.
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Old 01-13-2017, 09:14 PM
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Originally Posted by Kelly O View Post
Not specific to Fountain, all 600/700sci's are prone.

Had an IAC failure second season after getting boat, knew from reading to kill ignition power immediately to save ECM. Been replacing IAC's every other year now, cheap insurance to eliminate failures.
Kelly, did you do the 1 amp fuse on the power to the IAC?
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Old 01-14-2017, 07:16 AM
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Originally Posted by VoodooRob View Post
Kelly, did you do the 1 amp fuse on the power to the IAC?
Did not do the fuse, figured I would just replace IAC's every other season and not have any failures. If I remember correctly, Smartcraft gave a low voltage warning for the idle control circuit which I believe was caused by the old IAC drawing high amps from being carboned/gummed up.

Have not seen that warning since replacing valve regularly. I viewed the fuse as protection for neglecting to replace IAC's, a known and well documented service concern. Thought it better to do preventative maintenance than reactive, in order to protect wiring harnesses and ECM.

The fuse is a great way to protect the ECM during an IAC failure, I've just decided to follow a replacement schedule which eliminates failures.
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Old 01-14-2017, 08:39 AM
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That would be one more think to try to remember not good for me .
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Old 01-14-2017, 09:28 AM
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Originally Posted by Kelly O View Post
Did not do the fuse, figured I would just replace IAC's every other season and not have any failures. If I remember correctly, Smartcraft gave a low voltage warning for the idle control circuit which I believe was caused by the old IAC drawing high amps from being carboned/gummed up.

Have not seen that warning since replacing valve regularly. I viewed the fuse as protection for neglecting to replace IAC's, a known and well documented service concern. Thought it better to do preventative maintenance than reactive, in order to protect wiring harnesses and ECM.

The fuse is a great way to protect the ECM during an IAC failure, I've just decided to follow a replacement schedule which eliminates failures.
Hi Kelly O, where exactly is this IAC, how much are they worth and do you know if this is still a problem with latest 700's ? I am also very big on preventitive maintenance but have not really heard of this failure .
Thanks, Mark
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