84 SN2001 Voltage Drop |
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maxibarker ![]() Newbie ![]() Joined: July-21-2009 Location: Discovery Bay Status: Offline Points: 8 |
![]() ![]() ![]() ![]() ![]() Posted: September-24-2017 at 3:21pm |
Shouldn't my electrical system be able to overcome the load of a small Rule bilge pump, and the OEM blower? I have great hole shot with these loads off, and stumbling, and stammering when I stab it with these loads on. Nominal voltage is 12v, but when loads are on it drops to 10.5. Shouldn't the available voltage regulate to maintain nominal 12v? My solution is obvious, loads off generally. But seems to me that when this boat was new I didn't have to do this. Thoughts?
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Gary S ![]() Grand Poobah ![]() ![]() Joined: November-30-2006 Location: Illinois Status: Offline Points: 14096 |
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Thoughts? do a search,common problem with all makes. You need new feeds to the dash,much like people needing a heart bypass
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10774 |
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Sounds to me like a nominal voltage of 12 is low and maybe your alternator/voltage regulator have issues.
You should have 13 to 14 or so at the battery itself (measured with a multimeter) with the engine running and a little less at the dash. If that 12 is on your dash meter, it's too low What do you have for an ignition system? points or electronic. What brand if it's electronic? If it's electronic, depending on the brand, they can be finicky and do things like you describe if supply voltage is too low. It could be wiring related like Gary said or the alternator/regulator or a combination of both. |
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gt40KS ![]() Gold Member ![]() ![]() Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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* Failing alternator?
* Ground or power cable corrosion and/ or short? * Voltage regulator? Regardless, I would verify the exact running voltage with loads off to eliminate the possibility of a failing battery and that the alternator is supplying the correct voltage while running. It's a good starting point anyway. |
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JCCI
1995 Ski Nautique GT40 |
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maxibarker ![]() Newbie ![]() Joined: July-21-2009 Location: Discovery Bay Status: Offline Points: 8 |
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Thanks all. I did search the forum first but didn't come up with anything relevant. It's a new alternator with an integrated regulator as my "mechanic" suggested but no help. Also at his suggestion we changed out the loom resistor with a ballast resistor no help. And while we were at it we replaced the coil. Same result. It has points by the way, not EI. Will get the meter and check these suggestions and the battery is probably about 7 years old so will do a load test.
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gt40KS ![]() Gold Member ![]() ![]() Joined: August-05-2017 Location: Wichita Kansas Status: Offline Points: 943 |
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Battery is not to be ruled out, you're correct - stranger things have happened. As with the alternator ... brand new out of the box has been known to be faulty. I'd still check it.
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JCCI
1995 Ski Nautique GT40 |
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10774 |
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I'm kinda wondering what you have for an engine, since you mention having a loom resistor originally and I haven't seen any mention of the brand, like PCM Ford, Mercruiser Chevy for example.
The PCM Fords didn't have a resistor in the wire loom You could also check the big connector plug at the back of the engine, unplug it, clean the connectors and plug it back together. Power has to get thru that plug to get to the dash and back thru the plug to get back to the ignition system and corroded connectors can impact your voltage and current carrying capability. |
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maxibarker ![]() Newbie ![]() Joined: July-21-2009 Location: Discovery Bay Status: Offline Points: 8 |
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It's a Ford 351 Commander and it did have a loom resistance wire. I will clean all connectors while I try to find the problem. Thanks.
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KENO ![]() Grand Poobah ![]() Joined: June-06-2004 Location: United States Status: Offline Points: 10774 |
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I guess I won't put up Tim's PCM wiring diagram then, it may confuse things
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8122pbrainard ![]() Grand Poobah ![]() ![]() Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41040 |
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Confirming what has already been said, clean all your connections check voltage at the alternator and then at the dash with a VOM. Up sizing both the - and + wire up to the dash is common. Also add up your amp draw and run it through one of the on line calculators like this one. When sizing wire, take a look at the chart: ![]() ![]() |
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maxibarker ![]() Newbie ![]() Joined: July-21-2009 Location: Discovery Bay Status: Offline Points: 8 |
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Will do. Thanks all!
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