Electrical puzzle. PCM351W
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=2890
Printed Date: November-26-2024 at 10:21pm
Topic: Electrical puzzle. PCM351W
Posted By: Morto
Subject: Electrical puzzle. PCM351W
Date Posted: January-17-2006 at 4:18am
| Hi again all, thanks for the replies to my last! This time I can't figure out how to wire the engine circuit breaker (the 40amp one that mounts on the back). In the PCM manual (same one that's on this website) the electrical schematic has a drawing of the start relay (mine has no solenoid on the starter) with the main cable coming from the battery, the main cable going to the starter, the small wire coming from the start switch (via the neutral safety switch) and the small wire going to the ballast resistor. Fine so far but the breaker seems to be attached to the same terminal as the main cable coming from the battery, which to my way of thinking is useless if the starter is hotwired to the battery. Can anyone help with this one? (By the way, this thing was in many pieces when we bought it so I didn't see the original set-up). Thanks again. |
Replies:
Posted By: 79nautique
Date Posted: January-17-2006 at 6:04am
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Do you have a Amp gauge or a Volt gauge? And what Yr engine? Depending upon the type of gauge you have it is wired a little different. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: nuttyskier2002
Date Posted: January-17-2006 at 6:04am
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One terminal of the circuit breaker should go to the battery (via the cable mounted to the starter relay). The other terminal should go to the output of the alternator. All other electrical connections coming from the alternator output should be on the protected side of the circuit breaker. The circuit breaker protects your charging system and really has nothing to do with the starting circuit (other than it handles the current that charges the battery). Make sure your circuit breaker has not been bypassed! ------------- 95 Malibu Echelon w/Mercruiser 350 Magnum Skier Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
Posted By: nuttyskier2002
Date Posted: January-17-2006 at 6:09am
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Your right 79, forgot about that detail. The above post is basically correct, however you may also have an amp gage wired in between. ------------- 95 Malibu Echelon w/Mercruiser 350 Magnum Skier Former boats: 88 Ski Centurion Tru Trac II 59 Chris Craft Capri (woody) |
Posted By: Morto
Date Posted: January-17-2006 at 9:48am
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Gotcha. Forgot to mention also that mine has a single wire alternator (internally regulated - definately not original) and uses an ammeter.
So I take it that seeing as the output from the alternator isn't shunted directly to the battery, the breaker goes inline between alternator output and the ammeter? Starting to sound logical now........ Thanks. |
Posted By: JEFF KOSTIS
Date Posted: January-17-2006 at 8:07pm
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No matter what, one side of the breaker is a large cable directly to the batt + cable or starter hot all the time (feed). There should be nothing connectd along with this. All of the accessory feeds go on the other side of the breaker.
The purpose: batt is capable of 1000 amps at dead short. If something shorts like the alt, or wiring, the breaker will trip preventing fire. They are then fused again individually at the dash. Think of it like house wiring. Power comes in the house to a main breaker, then distibuted via smaller breakers or sub-feeds. GOOD LUCK!! Jeff ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: 79nautique
Date Posted: January-18-2006 at 6:57am
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Knida confused by Jeff's comments and think he is talking about the relay and not the breaker. What I remember is there are two 10 or 8 gauge wires going to the breaker and the battery + cable goes directly to one side of the relay then the other side of the relay goes directly to the starter. One side of the breaker is for a red wire out of the wiring harness directly from the alt I believe, then the other side of the breaker goes to the relay. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: JEFF KOSTIS
Date Posted: January-18-2006 at 8:25pm
I am talking about the breaker and not the relay. All PCM engines that Ive seen have the big breaker. The main pupose is to prevent a fire due to short or malfuction. If it were direct drive off the batt(no breaker in between), then if a overload occured, it would burn the wiring and possibly start a fire. Hopr this helps!!  ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: 79nautique
Date Posted: January-19-2006 at 6:36am
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I would suggest that you to refer PCM manuals in the reference section and look at the wiring diagrams.
How many amps does a start draw? <30? <50? >50? I'm guessing over 50 amps and if I put a 30 or 50 amp in series with it then it's going to trip every time the starter is engauged. Check out the manuals. .02 ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: JoeinNY
Date Posted: January-19-2006 at 8:31am
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A typical starter under load will draw 250 plus amps, thats once moving (neglecting inrush current), on a summer day with a fairly low compression motor. The connection between the battery and the starter motor doesn't ever go through a breaker, it wouldn't work if it did, for a breaker in that circuit to provide any fire protection it would have to be so small that it wouldn't allow the massive starting inrush currents. the only reason the starting circuit doesn't set the boat on fire is the inherent intermittant nature.
The big breaker in question protects all other circuits by residing between them and the battery positive I believe that is inline with what everyone has said but I can see how there could be confusion.. -Joe. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=1477 - 1983 Ski Nautique 2001 1967 Mustang 302 "Decoy" http://www.youtube.com/watch?v=cO5MkcBXBBs - Holeshot Video |
Posted By: 79nautique
Date Posted: January-19-2006 at 9:02am
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I guess since he has a single wire from the alt (new style/conversion) then that wire would go directly the the curcuit breaker then that would go to the solenoid or relay depending upon which type of starter you have (ford/gm) and that would be a battery (+) wire 8-10 ga. but there is also a battery (+) cable 0/2 ga. that goes directly to the relay or solenoid depend again on which make and type start the engine has maybe that the confussing factor???
.02 ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: JEFF KOSTIS
Date Posted: January-19-2006 at 8:21pm
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You are all correct and thank you for correcting the confusion. The starter motor is always direct off the battery, while the breaker feed is hooked at that same point. JoeinNY cleared up what I was getting at. Everything but the main batt cable/starter is protected by the breaker. Sometimes installing a larger alternator than the original (usually 37 A) might cause the 50 amp breaker to trip.
Example: 87 amp new alternator with a drained battery (due to running a stereo with the engine off) would cause the alt to charge the batt at lets say 70 amps for 10 seconds. This would trip it, and the motor dies. Another breaker or fuse with the correct wire size would have to be installed in parellel. Ok this is enough techno stuff...sorry Jeff------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: Morto
Date Posted: January-23-2006 at 8:15am
| Not at all!! Thanks everyone, once this beer wears off I;m gonna read it all again and then go out to the carport.....By the way, my man has just told me to ditch the ammeter and go with a voltmeter (wish he had told me a few months ago, ##$#!!). Seriously though, thanks. |
Posted By: 79nautique
Date Posted: January-23-2006 at 8:50am
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I would go with what gauge is currently wired in, that way it will be much easier to follow and less work rewiring. But if you are starting from scratch or re-doing everything then it doesn't matter use what you like. I like the amp gauge that way I know what the draw is on the battery and thats more important to me than knowing if there's 12 or 14 volts in the system. .02 ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: Morto
Date Posted: January-23-2006 at 6:21pm
| Sure 79, I was thinking along those same lines but seeing as the entire harness was thrown away and we are starting from scratch the strong recommendation was to use a voltmeter then the output goes directly to the start relay (only about 1 1/2 feet). The alternator has an output for a warning light which will at least tell us when the battery is discharghing. Incidently, we are using elevator cable. The cable is neopreen and not harmed by water/oil etc, and there's 11 individually numbered wires plus an earth. It's pretty neat. |
Posted By: JEFF KOSTIS
Date Posted: January-23-2006 at 7:17pm
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A voltmeter can be installed easily. If you do a volmeter (which is still ok), I would suggest running seperate ground and hot wires to it from the batt cable and ground on the engine. This is because it will give you a low inaccurate system voltage reading if connected at the dash due to the voltage drop in the wiring. SOOOOOO many boats read 13-14 volts until the blower and lights are turned on. Then the gauge will read 12.5 which isnt good, but in reality its ok because the voltage at the batt cables are still at 13.8 or so. Remember to run large (#8 awg) wire minimum for the hot and ground that feeds the dash.
Jeff... ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: Morto
Date Posted: January-25-2006 at 12:07am
| Thanks Jeff, the plan is to run two large wires from the battery to a main cut-off switch at the dash and take the voltmeter pickoff from here. The feed will then go to a fusebox and off to all the circuits. Sound OK? |
Posted By: JEFF KOSTIS
Date Posted: January-29-2006 at 8:54pm
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Make sure the feed wires are large enough!! At least #8 awg. Its better to run the ground wire for the voltmeter back to the engine block to eliminate reading the voltage drop in the ground feed wire as well. Remember to hook the voltmeter after the ign key so it doesnt run all the time and kill the batt. The ultimate is to hook the voltmeter to the main batt cable and use a relay tied to the ign key so what you read is REAL. Issues occur when accys are on and you start reading low voltage due to the voltage drop in the wire--- thats inaccurate. Plus, If you read 14v, then in a few years you run it and it says 13, you might need alt work cause its not keeping up with the load. ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: JEFF KOSTIS
Date Posted: January-29-2006 at 9:03pm
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Oh yeah, make dam sure you fuse (or breaker) the main feed hot wire at the engine. A 60 amp is usually a safe short circiut protection for # 8 wire. Your engine may already have it, but be sure!! Keep the unprotected wire on the engine as short as possible, and put it in black split wire loom for extra protection!!
I just read that you have a 40amp breaker already in the boat, then you are golden!! Jeff...------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: Morto
Date Posted: February-13-2006 at 6:30am
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"I just read that you have a 40amp breaker already in the boat, then you are golden!! Jeff..."
Jeff, I think it's actually a 60amp. It's a Japanese alternator (I've filed the Mitsubishi diamonds off the back of it before we paint it - got nothing against Mitsu, it'll be towed by one, just can't have it on that engine!) Sounds like it's way over the top for this setup but it was there when we got it......... |