Possible low voltage problem

[Tail_Gunner]

This is a first...2001 4.3 GI Fuel injected PEFS. the boats gauge show's 11/12 volt output....The Gps chimes in with low battery. Voltage at the battery 12+ and the altenator give a solid 13.9 volts...The regulator is in the altenator so that cant be srewy...I am getting older but my brain is at a loss here...Bad ground on the bus bar????

 

[Don S]

Re: Possible low voltage problem

If it's 13.9 at the alternator, what is it at the starter terminal (not the wire ends them selves, the starter solenoid terminal), then check the orange wire terminal they all the same?
If still 13.9 at the starter and 12 at the battery, then something between the starter and the battery is at fault.

 

[Tail_Gunner]

Re: Possible low voltage problem

Sorry for the delay..Ok altenator 14.1 starter 13.98 battery 12.8 engine off and 14.0 when the motor is running...gauge shows 12.2..Can i take a reader and meausre the gauge or is it cut down there.

 

[Don S]

Re: Possible low voltage problem

Hook your DVM to the + and - terminals on the back of the gauge and see if it agrees with the gauge. Engine running and not running.

 

[Tail_Gunner]

Re: Possible low voltage problem

10.78 off 12.8 on gauge is reporting right....alt 14....starter 13.9..There are some solenoids setting in front the TBI they seemed warmed.

 

[Jlawsen]

Re: Possible low voltage problem

10.78 off 12.8 on gauge is reporting right....alt 14....starter 13.9..There are some solenoids setting in front the TBI they seemed warmed.

Tail Gunner, that sure sounds like a sulfated battery to me. I'm just guessing but if it was me I'd take it in and have it tested. If nothing else it would eliminate it. I'm hesitant to call it a bad ground because your alternator output seems normal. Usually, when you have a bad ground that close to the charging system, you'll see the alternator spiking with some really high voltages.

 

[Tail_Gunner]

Re: Possible low voltage problem

Removed the old battery placed a new on in. ALt now reads 14.1 battery 14.1 gauge and power leads to the gauge 12.9 motor running...No more low voltage on the gps but will the circut even send 14 volts to the gauges.

 

[Jlawsen]

Re: Possible low voltage problem

Put a load on the battery for a short period of time. That will burn off any surface charge and it should settle at 12.6v. Now start the motor and fire of your electronics for a while. Shut it off and check the battery voltage. It will likely be between 12.8 and 13.3. What this is telling you is that the voltage sensing circuit in your rectifier/regulator is working perfectly and that your battery is being properly charged. You should be able to rest easy.

Also, the voltages you are reading are telling you that the Alternator is seeing a well connected circuit (proper load) and is outputing a voltage level that is consistant and appropriate. Essentially, you have no bad grounds.

 

[Tail_Gunner]

Re: Possible low voltage problem

Well your right..took it down and bang 13.5 volts on the gauge. Havnt seen that for a year..Sulfated battery hmmm havnt heard that for a very long time.

 

[bruceb58]

Re: Possible low voltage problem

You have a resistive connection between the engine and the helm.

Measure the voltage between the positive of the battery and the positive of your gauge. The do the same between negative terminal of the battery and the negative busbar or negative side of the gauge. The side with the 1V drop is the culprit. I would suspect the main engine harness first.

 

[Tail_Gunner]

Re: Possible low voltage problem

You have a resistive connection between the engine and the helm.

Measure the voltage between the positive of the battery and the positive of your gauge. The do the same between negative terminal of the battery and the negative busbar or negative side of the gauge. The side with the 1V drop is the culprit. I would suspect the main engine harness first.

I am truly the village idiot when it comes electronics...Arnt you talking resistance???

 

[bruceb58]

Re: Possible low voltage problem

Yes but measure the voltage drop with the circuit active is the besy way to look for it. You basically can't measure this with a meter in the ohms setting. This is the easy way to do it.

By measuring both the positive voltage drop and the negative voltage drop you can see which side of the circuit has the problem which cuts your troubleshooting in half.

 

[Tail_Gunner]

Re: Possible low voltage problem

You have a resistive connection between the engine and the helm.

Measure the voltage between the positive of the battery and the positive of your gauge. The do the same between negative terminal of the battery and the negative busbar or negative side of the gauge. The side with the 1V drop is the culprit. I would suspect the main engine harness first.

Ok So engine off mesure the battery..then the gauge Orr....How does one measure voltage on the postive of the gauge to the positve of the battery that's one long test wire....Told you...Your trying to talk to a childs mind here..

 

[bruceb58]

Re: Possible low voltage problem

Measure everything with the engine running.

Yep...its a long test lead. You will need to make a long test lead with alligator clips on each end.

 

[Tail_Gunner]

Re: Possible low voltage problem

Ok i did read it right will do Bruce thank you..Finsihing a carb now so it will be a couple of hours.

 

[Tail_Gunner]

Re: Possible low voltage problem

After reading your post Bruce i decided to check as many components as possible...Bad bilge pump...bad horn...Relay's in front of the TB were badly corroded new battery cables cleaned the power dist bank. Now reading 13.5 volts and the main power connection is next..most all of my connections when checked where facing pretty bad corrsion.

Even cleaned the spark arrestor...pretty clean on the outside but full of debis on the inner mesh actually boiled it clean on the barby and blew it out with both water and air....I think i picked up 2mph in the 3500 rpm range....

 

[Tail_Gunner]

Re: Possible low voltage problem

Well after all that over looked maintance i now have a interesting result. The trim gauge bounces every time i use something electrical and it bounces according to how much power is being drawn...aka blower motor mild bounce bilge pump nice bounce..horn jumps half the gauge. The trim system works fine and is dead on..Why the short or spike only on the trim gauge??

 

[Don S]

Re: Possible low voltage problem

Have you checked your main harness connection on the engine (Round 10 pin connector). That connector also has a clamp on it. DO NOT over-tighten that clamp. It will distort the connector.

 

[bruceb58]

Re: Possible low voltage problem

Also make sure you have the cable connections at your starter are perfectly clean. Take them all off and sand to bare metal and reinstall. Do the same with your negative battery connections at the block.

The trim sender likely has its reference voltage in a different spot than the dash and that is why you see the spike.

 

[Tail_Gunner]

Re: Possible low voltage problem

So the main harnes is all good no deformation no oxidation.
All cables are clean as whislte

Ing key off trim gauge nice spike with blower on
Ing key ON trim.. gas.. voltage gage... give a small spike

Now oil and water gauges...no spikes.


The trim sender likely has its reference voltage in a different spot than the dash and that is why you see the spike.

So this then if not a problem???