charging system

[Andy in NY]

1970 evinrude 85 hp

this morning when getting ready to go to the lake i went to start it and it was a little slow cranking, but started okay. got to the lake and started, slow cranking as well. went out on the lake and ran around for about 30 min (i figured i would give it time to charge) and stopped to let someone on the tube and she would barely crank and didnt start. luckily i carry jumper cables. got a jump and it fired on the first crank.


this past week i did a bit of working on it, a fair amount of tilt up and down.


is this a battery issue or a charging issue? i know barely anything about electrical systems.

btw i dont run any accessorys except for power tilt and a depthfinder.

 

[Vic.S]

Re: charging system

Check/clean all connections. Don't forget the negative ground connections as well.

Charge the battery and check the volts across it. If fully charged and in reasonable shape you should get around 12.8 volts after it has rested with no charging and no load for 12 hours.
If you can let it stand for longer you'll find that the volts will drop fairly quickly at first then more slowly. A good battery holding its charge should not drop much more than 0.1 volt in the first 7 - 10 days

It would be a good idea to get the battery load tested as that will confirm that it will still deliver the amps required to operate the starter.

When refitted to the boat monitor the volts at the battery terminals. They will drop while the starter is operated but should quickly recover and if it is charging will soon rise to around 14 volts. If they do not rise then the charging system is not working. ( defective rectifier perhaps)

It is a non-regulated system so if all is well the volts will rise above 14 possibly to 16 or more eventually.

 

[Andy in NY]

Re: charging system

Check/clean all connections. Don't forget the negative ground connections as well.

Charge the battery and check the volts across it. If fully charged and in reasonable shape you should get around 12.8 volts after it has rested with no charging and no load for 12 hours.
If you can let it stand for longer you'll find that the volts will drop fairly quickly at first then more slowly. A good battery holding its charge should not drop much more than 0.1 volt in the first 7 - 10 days

It would be a good idea to get the battery load tested as that will confirm that it will still deliver the amps required to operate the starter.

When refitted to the boat monitor the volts at the battery terminals. They will drop while the starter is operated but should quickly recover and if it is charging will soon rise to around 14 volts. If they do not rise then the charging system is not working. ( defective rectifier perhaps)

It is a non-regulated system so if all is well the volts will rise above 14 possibly to 16 or more eventually.

The connections are good, the battery cables are both brand new and i just cleaned the contact points for the pos that goes from the solinoid to the starter.

with the motor running, the voltage according to the depth finder was 12.6


if i have a faulty recitifer or something else in the charging system, how do i find out what?

 

[Andy in NY]

Re: charging system

is there a sure fire way to check for charging at idle?

 

[Vic.S]

Re: charging system

At 12.6 volts you are not charging. You have got to have around 14.

Id rather check at the battery terminals with a separate voltmeter though.

Check also at the red lead from the rectifier.

You can test the rectifier by following Joe Reeves' instructions on the Engine FAQs board.
BUT if you use a digital meter use it on the "diode test" setting not on an ohms range because they don't all work for diode testing on all the ohms ranges.

No problem with analog meters

 

[Andy in NY]

Re: charging system

At 12.6 volts you are not charging. You have got to have around 14.

Id rather check at the battery terminals with a separate voltmeter though.

Check also at the red lead from the rectifier.

You can test the rectifier by following Joe Reeves' instructions on the Engine FAQs board.
BUT if you use a digital meter use it on the "diode test" setting not on an ohms range because they don't all work for diode testing on all the ohms ranges.

No problem with analog meters

okay so apperantly i havent a clut how to use my new digital multimeter! where do i want to set it for this testing?

 

[Andy in NY]

Re: charging system

few things i forgot to ask/mention...


the battery load tested ok at auto zone.


if it is my charging system, what will need to be replaced... the stator? or the rectifier?

 

[Vic.S]

Re: charging system

okay so apperantly i havent a clut how to use my new digital multimeter! where do i want to set it for this testing?

Use a suitable DC volts range ( probably 20 volts ) to check the volts across the battery and also between the red lead of the rectifier and ground.

At both places you should see 12.something volts. The reading will fall during cranking but should soon recover. If it is charging the volts will recover quickly and rise to around 14 or even higher eventually. If they do not rise it is not charging.

Use the diode test range for testing the rectifier, otherwise following Joe Reeves' instructions.

You can also check the stator using an ohms range. You should get a fairly low reading between any two of the yellow wires. If you don't then the stator is open circuit.

 

[Andy in NY]

Re: charging system

thanks vic you have been a big help so far. ill be working on this later this afternoon... but the big picture is all starting to come together now. i just read the post on testing the rectifier and tachometer to see wich is faulty... and it hit me that the tach i installed 2 weeks ago isnt working.

 

[Dabbler_E]

Re: charging system

Not charging + tach not working = smells strongly of a bad rectifier.

I learned this by blowing mine accidentally (as a newbie, when I knew not what I did) by disconnecting and reconnecting the battery with the key switch on.

Joe Reeves' rectifier testing procedure is HERE

 

[Andy in NY]

Re: charging system

Not charging + tach not working = smells strongly of a bad rectifier.

I learned this by blowing mine accidentally (as a newbie, when I knew not what I did) by disconnecting and reconnecting the battery with the key switch on.

Joe Reeves' rectifier testing procedure is HERE

really, thats all it can take to blow it? now that i start to think of it, theres probably 5 or 6 different things that i did that could have blown it. i know ive disconnected the battery with the key on several times (but motor not running), and when i was installing the tach i accidentally hit the pos and sig poles together while tightening the nut that holds the wire on.


i just ordered one that will be in tomorrow, and if its something else at least i will have a spare rectifier hanging around.

 

[Andy in NY]

Re: charging system

okay here are my results:


battery with multi meter: 12.6 volts with engine off. with engine running, the display jumps around like crazy, so fast that i cant even read the numbers.

same with readings from the rectifier to ground. if i even put my multi meter near the engine it went wonky.

 

[daselbee]

Re: charging system

Gotta weigh in here.
1. Key on when connecting or disconnecting the battery will not blow the rectifier.
The positive battery cable runs from the batt to the starter solenoid large post. The rectifier red wire is also directly connected to the same large post. So, the key switch has no effect on anything in the rectifier's red wire circuit. None.

2. Accidentally shorting the 12v battery voltage to the gray tach signal wire as you described could likely blow the rectifier.

3. You need serious lessons on the use of a mulitmeter. When measuring voltages, always set the meter to a scale settting that is one switch setting higher than the voltage being measured. For example, when measuring 12v dc, set the meter for the next setting higher than 12v, which is probably 20v, but can vary depending on the meter in use. When measuring house current, which is 120v AC, set the meter for AC volts, and the proper switch selection that is higher than 120, which may be 300 for instance. Depends on the meter.

When measuring for continuity, or for exact ohms readings, never measure the circuit with the power on. You can blow the meter, again depending on the meter's quality (input protection ability). Using a digital multimeter on diodes almost always requires that you use the diode check switch selection, because this allows the meter to provide enough current to forward bias the diode being checked.

If you were to "ohm out" the stator, use regular resistance scales, again setting the range just higher than the expected value. You expect 500 ohms, then set the meter scale to 1k. Example only. Depends on your meter.

 

[Andy in NY]

Re: charging system

Gotta weigh in here.
1. Key on when connecting or disconnecting the battery will not blow the rectifier.
The positive battery cable runs from the batt to the starter solenoid large post. The rectifier red wire is also directly connected to the same large post. So, the key switch has no effect on anything in the rectifier's red wire circuit. None.

2. Accidentally shorting the 12v battery voltage to the gray tach signal wire as you described could likely blow the rectifier.

3. You need serious lessons on the use of a mulitmeter. When measuring voltages, always set the meter to a scale settting that is one switch setting higher than the voltage being measured. For example, when measuring 12v dc, set the meter for the next setting higher than 12v, which is probably 20v, but can vary depending on the meter in use. When measuring house current, which is 120v AC, set the meter for AC volts, and the proper switch selection that is higher than 120, which may be 300 for instance. Depends on the meter.

When measuring for continuity, or for exact ohms readings, never measure the circuit with the power on. You can blow the meter, again depending on the meter's quality (input protection ability). Using a digital multimeter on diodes almost always requires that you use the diode check switch selection, because this allows the meter to provide enough current to forward bias the diode being checked.

If you were to "ohm out" the stator, use regular resistance scales, again setting the range just higher than the expected value. You expect 500 ohms, then set the meter scale to 1k. Example only. Depends on your meter.

it is set to 20v.


so how do i test the rectifier then if i am not supposed to measure with it on???

 

[daselbee]

Re: charging system

I said when measuring resistances or continuity the circuit must not be powered on.
If the power is on when measuring resistance, you will likely blow the meter, and if it doesn't blow, you won't get a valid resistance reading anyway.

When measuring voltages, the circuit is powered on.

Maybe you haven't seen the rectifier testing procedure where you test resistance between rectifier leads in various combinations...red to gnd, reverse lead polatity and measure again...etc. Have you not seen that?
Those tests must be done with the power off, and if it were me, with the rectifier off the motor and on the bench, or at minimum with all leads disconnected and free floating, not touching anything at all.

 

[daselbee]

Re: charging system

Not charging + tach not working = smells strongly of a bad rectifier.

I learned this by blowing mine accidentally (as a newbie, when I knew not what I did) by disconnecting and reconnecting the battery with the key switch on.

Joe Reeves' rectifier testing procedure is HERE

Here is the resistance checking method that Dabbler posted for you earlier. Note the directions say to disconnect the leads, and to use the ohmmeter, and that you are testing diodes.
Therefore, no power on the circuit, and use the diode check feature of your DVM if you have one.

 

[Vic.S]

Re: charging system

with engine running, the display jumps around like crazy, so fast that i cant even read the numbers.

Now that is not what I was expecting at all.
Puzzled now.

I think the way forward is to test the rectifier as described by Joe Reeves
Simple three wire type. Red, yellow and yellow gray.

The best bet is to remove the rectifier in order to test it but there is no reason why it should not be disconnected and tested while still in position. Make a written record of all the connections so that there is no possibility of reconnecting things wrongly

On what others have said:

It is right that disconnecting the battery with the key switch on will not harm the rectifier.
However disconnecting the battery while the engine is running could do so.

I do not think accidentally shorting the battery to the gray tach wire will harm the rectifier.

What will destroy the rectifier in an instant is connecting the battery the wrong way round! ( not done that I suppose?)

 

[Andy in NY]

Re: charging system

Now that is not what I was expecting at all.
Puzzled now.

I think the way forward is to test the rectifier as described by Joe Reeves
Simple three wire type. Red, yellow and yellow gray.

The best bet is to remove the rectifier in order to test it but there is no reason why it should not be disconnected and tested while still in position. Make a written record of all the connections so that there is no possibility of reconnecting things wrongly

On what others have said:

It is right that disconnecting the battery with the key switch on will not harm the rectifier.
However disconnecting the battery while the engine is running could do so.

I do not think accidentally shorting the battery to the gray tach wire will harm the rectifier.

What will destroy the rectifier in an instant is connecting the battery the wrong way round! ( not done that I suppose?)

i have not ever connected the battery backwords.


i tested the rectifier with the ohms meter and got NO READING in either directions according to the troubleshooting guide.

 

[Vic.S]

Re: charging system

i tested the rectifier with the ohms meter and got NO READING in either directions according to the troubleshooting guide.

You may have a defective rectifier then. BUT we did say use the diode test range because with the ohms ranges you most likely get no readings anyway.

If you do not have a diode test range try the very highest ohms range ... that works on my meter. Thats the 2000k ( 1 megohm) range.

If you still don't get a reading at all one way then assume it's dud. For each pair of connections tested you must get a reading one way and no reading the other way. ( You can actually forget about testing between red and the case .. tells you nothing extra. Red and each yellow, and case and each yellow is what counts.)

BTW is there a fuse anywhere in your motor wiring? If so check that. May be a 20 amp one there somewhere.

 

[Andy in NY]

Re: charging system

vic, i did use the highest ohm setting while doing the test.


i have a new rectifier coming today, so we'll see what happens.