General Electrical troubleshooting ?s

[QC]

I am having an issue with my boat's electrical system and need some diagnostic direction. I am kind of an electrical idiot, but I can use a multi-meter.<br /><br />I initially noticed that the running lights are drawing excessive voltage. When I have them on, voltage drops well below 12 volts (10.5) even with the engine running. I have to run above 1000 RPM to get back to 12 volts, better with both batteries on than single. Basic green and red on the bow and a standard stern light, no docking lights. Blower seems to draw too much as well. With the lights off, I can run the stereo, GPS, depth sounder etc. and the Merc 65A alternator (6.2 MX) keeps it at almost 14 volts. Well above 12 even at idle.<br /><br />I have also noticed that my gauges are all affected by turning on accessories. Whenever I hit the lights or the blower or trim tabs or drive trim there is movement on my temp gauge, trim gauge etc. This even happens with the key off and the gauges all off!! Temp moves, trim gauge starts moving down when I hit accessories. Batteries on, key off, gauges off, lights off; hit the blower, gauges move, blower off, hit the lights, gauges move. I can get the trim gauge to read anything I want by hitting the lights and then turning them off when the trim setting is where I want to "set" it (gauge only, I have not touched the trim button); if I turn the key on (no accessories on) the trim gauge returns to the correct position. With the engine running I get what appears to be slightly more trim down and higher temp when I hit the lights, again gauges only, the drive has not moved.<br /><br />What I have done so far: I pulled the fuses out of my GPS and depth sounder (I installed both so suspected them first) with no change to the freaky gauge stuff. I have checked voltage at each gauge's ground by using the hot lead at the ignition (all read 12.4ish key off). I have verified that my voltmeter is correct by comparing with voltage read on my GPS and my multi-meter. I have taken each bulb out of the running lights one at a time with no real impact except a very slight voltage blip up from removing the tiny load of each bulb. <br />Couple of other notes: batteries are individually holding a charge above 12 volts for 3 - 4 weeks easy. When I bought the boat (3 years ago), I saw something similar while inspecting. The previous owner said he would fix it, he called me later that day and said he had fixed it by playing with some ground wires. I confirmed that it indeed was "fixed" when I picked her up. I just changed my bilge pump that had totally fried due to an unknown issue. The bilge pump has the least affect on any of this. Gauges acted as above with new and old pump. It does not appear to be related, although I do not believe in coincidences much . . .<br /><br />Sorry about the long post, just wanted to give all the potentially related info. I don't know what to check next . . .

 

[RubberFrog]

Re: General Electrical troubleshooting ?s

I was thinking ground and then you mentioned a)previously had this problem due to ground, b)new bilge pump.<br /><br />How is the automatic float wired in? Have you quadruple checked it? Check it again. Completely unhook the new bilge pump and try checking it. It really sounds like a ground issue. Perhaps float power to ground?

 

[QC]

Re: General Electrical troubleshooting ?s

RF,<br /><br />I have done most of this testing with no bilge pump (in-between old and new, boat sitting on trailer). No float switch since boat was new(another topic, no need to go there now). Some testing with fuse out of bilge circuit. Getting good voltage and the pump now works fine, no change before and after. All connections to the new pump check out. Gauges only barely act up with bilge pump switch on/off. Nothing compared to impact of blower and running lights.

 

[MrBigStuff]

Re: General Electrical troubleshooting ?s

>drawing excessive voltage<br /><br />No such thing. Voltage is a measure of potential to do work. It is not consumed.<br /><br />The first step is to test the battery to insure it is capable of supplying the current demand without losing terminal voltage. This can be done by checking the specific gravity of the electrolyte or by load testing the battery.<br /><br />If the battery checks out, what is likely happening is that you have a bad/corroded connection somewhere common to all these circuits. When you energize them, they begin to draw current. As they draw current through the bad connection, it heats up. As it heats up, it's resistance goes up and so more voltage is dropped across the bad connection. You see the accessory terminal voltage go down during this time.<br /><br />You can visually inspect for bad connections or use the resistance measuring function of your meter to locate them. Be sure to disconnect the power source prior to measuring resistance of the circuits.

 

[tommays]

Re: General Electrical troubleshooting ?s

What happens with the trim PUMP ? at over 100 amps its the only really big draw on most boats AND is on its own battery cables <br /><br />How far above 12 ? 12.6 + is pretty good if your holding around 12.4 or less its a pretty big difference in the batterys abilty to pass amps<br /><br /> I work on a lot of floor scrubbers and electric lifts ,we do a lot of hydrometer checking on the batterys and the hydrometer readings tend to back up those voltage figures as to when the batterys have seen better days<br /><br />tommays

 

[QC]

Re: General Electrical troubleshooting ?s

Originally posted by MrBigStuff:<br /> drawing excessive voltage<br /><br />No such thing. Voltage is a measure of potential to do work. It is not consumed.

Like I said, electrical idiot. Voltage drops dramatically, would be more correct then.<br /><br />

Originally posted by MrBigStuff:<br /> Be sure to disconnect the power source prior to measuring resistance of the circuits.

Help me here. I can check resistance with no power to the circuit? Just check resistance between two points with battery switch off?

 

[QC]

Re: General Electrical troubleshooting ?s

I saw 12.57 yesterday across "both" without adding any charge for a couple of days. So the fact that these batteries (either one)will hold a charge AND that she cranks easily etc. is not a good indicator? No hydrometer, seems to behave the same regardless of charge level. Will leave on charger for a few hours and report back voltage after that . . .<br /><br />No clues from the gauges off behavior?

 

[tommays]

Re: General Electrical troubleshooting ?s

It sounds like a bad connection <br /><br />Thats why i am asking about the TRIM PUMP if theres a problem with the batterys and ALT IT WILL really show up when you use it<br /><br />On a lot of boats with problems the trim will kill the motor it drops the voltage so far<br /><br />tommays

 

[QC]

Re: General Electrical troubleshooting ?s

OK, just checked before charger application and have 12.47 across "both". I have been fartin' around with this thing for about four days with no new charge. Hatch up, hatch down etc. I am getting 13.52 with 6 AMP charger on now. Same across the gauges, battery direct etc.<br /><br />Sorry missed the trim pump question. Moving too fast Trim pump causes exact same behavior as running lights, blower, trim tab pump and hatch ram (electromechanical, not hydraulic). Big voltage drop, but I have never seen the engine stumble although I have played with each of these together and separately 100 times trying to narrow it down.

 

[tommays]

Re: General Electrical troubleshooting ?s

If the trim pump cables are in good condition and have clean connections it points to getting a real load test on the battery<br /><br /> It is a self contained system and really makes a weak battery show up<br /><br /><br />tommays

 

[QC]

Re: General Electrical troubleshooting ?s

Is there a rule of thumb for voltage drop over time that can be used as a load test? I can pull them out, but I have been able to start this thing without a charge as long as six weeks after putting her away. That was leaving the switch on purposely to try and kill them . . .

 

[tommays]

Re: General Electrical troubleshooting ?s

I can only say that my last 8 year old battery started the boat fine BUT the new one started it a LOT finer <br /><br />How old are they ?<br /><br />tommays

 

[QC]

Re: General Electrical troubleshooting ?s

I think they are original. She is a 2001.

 

[tommays]

Re: General Electrical troubleshooting ?s

At 5 years they have given a good service life for a marine application <br /><br /><br />Unless you get a dead cell a batterys deterioration is pretty subtle<br /><br /><br />tommays

 

[QC]

Re: General Electrical troubleshooting ?s

I agree with you, that's why I was trying to kill 'em . . .<br /><br />With that said, would battery condition come close to causing the issues I describe? Especially considering the gauge behavior with the key off? I just had 15 volts with the charger on (6 AMP) and same gauge behavior by simply hitting the running lights switch with the key off. I also hit up on trim pump just now and it only dropped to around 12 volts (charger off), I was reading 13 volts before trim experiment, ambient around 75 F.<br /><br />Not avoiding the battery discussion, I just want to understand as much as possible. Definite weakness in my technical experience . . .

 

[tommays]

Re: General Electrical troubleshooting ?s

With the littel charger i would guess the voltage is "floating" up there BUT the battery really is not putting out the amps<br /><br />Check your trim pump it "should" have its own cables dirrectly to the battery and is as close to a load test as you can do with out the tool because its amp draw is so high<br /><br />I run in to fuses all the time that will pass enough voltage to show on a DMV but not even light a small bulb <br /><br />tommays

 

[QC]

Re: General Electrical troubleshooting ?s

Yes, trim pump is wired correctly. I just retried the trimp pump test. Starting voltage (drive down) 12.64 both batteries on. While trimming up dropped to 12.08 and blipped back up to 12.10 while drive was still rising. When reached max height and the pump started really screaming it dropped to 11.52. Batteries recovered to 12.56 within 15 seconds.<br /><br />Edit: They have recovered to 12.62 after about 5 minutes.

 

[QC]

Re: General Electrical troubleshooting ?s

The batteries have hung all day at 12.62, even after a much more severe version of the trim pump test. Stabilised at 12.2 with the pump being cycled up and down. Dropped to 11.87 with drive at high tilt limit and up trim held briefly.<br /><br />I have realised that there is a .6 volt drop between where I am checking the voltage (battery switch) and my helm voltmeter with nothing on except the key. Also there is this same lower voltage across all of the gauges etc. Only dropping .25 volts at the batteries when I hit the lights, about 1.5 voltage drop when checked at the helm. All of the points at the helm are within .05 volts.<br /><br />I will check resistance at each point tomorrow. Should this be checked at the same places, hot and cold for each powered item?

 

[tommays]

Re: General Electrical troubleshooting ?s

i wait for a second BUT i think the battery is takeing to long to recover from a short run of the trim pump<br /><br />There is no reason it should not go right back to to 12.6 volts as soon as the pump is off<br /><br />tommays

 

[jlinder]

Re: General Electrical troubleshooting ?s

I would reccomend taking a step back,taking/recording a number of measurements, then looking at them.<br /><br />I suggest you measure:<br /><br />1. Voltage at battery with no load.<br />2. Voltage at battery with load (lights & acc on).<br />3. Voltage at fuse panel with load.<br />4. Voltage between fuse panel ground and battery neg. terminal with load (just use any wire to extend the multimeter)<br />5. Voltage at battery with load and engine running.<br /><br />This will give us what we need to help diagnose the problem. For example:<br /><br />A. A bad ground will cause excessive voltage to appear in reading 4.<br />B. A bad battery will show a big difference between readings 1 and 2.<br />C. A bad power lead will show with a big difference between readings 2 and 3.<br /><br />I know this sounds like a lot, but you should be able to do this in 15-20 min. In the end it is the fastest way to troubleshoot and the most reliable.