Low Voltage
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=683
Printed Date: November-25-2024 at 12:55am
Topic: Low Voltage
Posted By: marks
Subject: Low Voltage
Date Posted: July-29-2004 at 4:31pm
I have an 89 SN with the original alternator. The other night at the lake, I noticed that when I turned on my nav lights the voltage meter dropped below 12 volts. If I turned on the blower too, the voltage would drop to around 8 volts. With just the engine running, it normally runs around 13 volts. Is this a sign that my alterator is starting to die, or could I simply have a bad connection somewhere? Any suggestions on how to diagnose the problem?
Thanks,
Mark
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Replies:
Posted By: 64 Skier
Date Posted: July-29-2004 at 5:00pm
Sounds like your alternator is unable to keep up with the few amps of load that lights require...that or you've got a short. What does your voltage do when your cranking and really pulling the battery down? If your voltage while cranking is higher than the lights and blower I'd guess you have a short.
Use a Volt Meter and measure your alternator output. It should read 1-1 1/2 volts higher than the battery alone. If not, give the engine a few hundred more RPM to see if the circuit "excites" the alternator. Sometimes, idling around just doesn't spin the alternator fast enough.
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64 Skier
66" HO VTX and 67" HO Triumph
http://www.correctcraftfan.com/diaries/details.asp?ID=1071&sort=&pagenum=3&yrstart=1971&yrend=1975 - 71CC
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Posted By: Jeff
Date Posted: July-29-2004 at 5:26pm
I had the exact same problem in my '89, as did the mechanic at my Nautique dealer. When I turned on the lights and blower, the volt meter would drop, and the temperature gage would bump up 10-15 degrees. When I hit my spot light, the low voltage alarm started singing.
In my boat, the problem was in the grounding of the gages. All the dash gages had their grounds connected in series, then back to the ground block. There was enough resistance in the connections from gage to gage that I measured 1.5 volts from the ground block to the last gage. My solution was to connect each individual gage grounds directly to the ground block. I also ran an additional heavy gage wire from the battery (-) to the ground block. After doing this, the gages remain normal when accessories are turned on.
Hope this helps.
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http://www.correctcraftfan.com/diaries/details.asp?ID=398&yrstart=1986&yrend=1990 - 89SN
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Posted By: kenny g
Date Posted: July-29-2004 at 6:42pm
internal regulators ! the trio diode system.
3 diodes in series,1 goes bad and the other 2 are still working.enough to crank the mill over,but a drop when you pull the acc's.
like the ol gal i go rid of,she ain't puttin out enough !
rebuild the alternator !
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kenny g
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Posted By: marks
Date Posted: July-30-2004 at 1:27pm
Thanks for the input guys. I will take an external meter and and try and determine if its a gauge problem or if the voltage really is low.
64 Skier, when I crank the engine, the volt meter has always dropped low. Is this normal? It doesn't seem to be cranking slow and I don't have any trouble starting. With the key on and the engine not running, I get a reading of about 11 volts.
Jeff, when you had the grounding problem with your gauges, did it also effect the gas gauge? I have had my boat for 3 years and the gas gauge has always had problems.
Kenny G, my alternator has the external regulator. Would the diodes you mentioned be part of the external regulator or are they still internal to the alternator? If the problem does turn out to be the alternator or regulator should I consider upgrading to a new alternator with the internal regulator? The upgrade is kind of pricey.
Thanks,
Mark
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Posted By: Jeff
Date Posted: July-30-2004 at 2:56pm
Mark,
If memory serves, all the gages were affected, but my attention was mainly focused on the voltage and temp.
Jeff
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http://www.correctcraftfan.com/diaries/details.asp?ID=398&yrstart=1986&yrend=1990 - 89SN
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Posted By: 64 Skier
Date Posted: July-30-2004 at 8:47pm
You should have 12 volts, and it sounds like your gauges reduce the voltage as much as the starter does. Did you read the 11 volts with a Volt meter or your gauges?
I think Jeff is correct and your first efforts should be the ground wiring of the gauges. Then start up and test the alternator output.
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64 Skier
66" HO VTX and 67" HO Triumph
http://www.correctcraftfan.com/diaries/details.asp?ID=1071&sort=&pagenum=3&yrstart=1971&yrend=1975 - 71CC
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Posted By: marks
Date Posted: August-02-2004 at 1:30pm
Problem solved. It was a ground problem just as Jeff described. The ground bus for the gauges was essentially 14 wire segments crimped end to end. The volt gauge happened to be the last one in the chain. I ran a couple of new wires from the ground block and branched them out so that each gauge was no more than 3 segments away. The volt meter now functions correctly and shows about 14 volts when the engine is running regardless of how many accessories are on and reads a little over 12 volts when the engine is off. There does appear to be about 3/4 volt drop across my ignition switch. I don't know if this is normal.
My fuel gauge is still goofy, but its behavior is more like an intermittent break in the connection.
Thanks everyone for your input.
Mark
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