1987 70ETLH not charging

doh13

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Hi, I am trying to diagnose my 70 hp 2t charging issue and would appreciate some input from the pros
1. I have unplugged the 2 green wires from the lighting coil that go to the voltage regulator and checked the ac voltage with the motor running at idle and it seems to be 4v AC so its possibly the lighting coil?
2. The regulator shows (minus) -3v dc voltage when testing at the regulator fuse and the battery has a power draw of approx 0.3v but when i unplug the regulator fuse the battery has little to no power draw this might indicate the voltage regulator? .
3. With the voltage regulator fuse unplugged the starter will not turn but if the motor is running and i unplug the fuse the motor will stay running is this normal?.
 

boscoe99

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What you call the voltage regulator fuse is the same fuse that provides battery power to the key switch. If no battery power to the key switch, then the starter won't operate.

Your model motor does not need battery power to run. Only to crank the motor. That is why when you disconnect the fuse (no battery power to the key switch) the motor will not crank but it will continue to run. You could pull start the motor also in which case it would start and run.
 

boscoe99

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4 AC volts from the lighting coil is way too low. Assumption being the lighting coil was unloaded when taking the measurement.

Have you tested the ohms of the lighting coil? Have you verified that the lighting coil is not shorted to ground?

Bad input to the R/R equals bad output from the R/R.
 

99yam40

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manual calls for measuring with a peak reading volt meter or an DVA adapter and a regular meter
it would be a good idea to get a service manual for you motor, and the proper test equipment
this is a little clip out of mine for a C40TLRX

1660482166186.png
 

99yam40

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notice spec in DCV, so that would require the proper test equipment
 
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doh13

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What you call the voltage regulator fuse is the same fuse that provides battery power to the key switch. If no battery power to the key switch, then the starter won't operate.

Your model motor does not need battery power to run. Only to crank the motor. That is why when you disconnect the fuse (no battery power to the key switch) the motor will not crank but it will continue to run. You could pull start the motor also in which case it would start and run.
Ahh thats a bit odd to me that that wire is needed for the starter but im glad you explained it I appreciate the info sir!
 
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doh13

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4 AC volts from the lighting coil is way too low. Assumption being the lighting coil was unloaded when taking the measurement.

Have you tested the ohms of the lighting coil? Have you verified that the lighting coil is not shorted to ground?

Bad input to the R/R equals bad output from the R/R.
I cant remember if i unplugged the 3rd wire from the lighting coil when I tested but i will check again and yes i do believe it was shorting to ground i will check that again though. thank you for the info.
 

doh13

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manual calls for measuring with a peak reading volt meter or an DVA adapter and a regular meter
it would be a good idea to get a service manual for you motor, and the proper test equipment
this is a little clip out of mine for a C40TLRX

View attachment 367928
I have read about the DVA adapter i might have to order one but I am guessing there could be an issue with the lighting coil I will check a few more things and hopefully can figgure it out with out the DVA thank you for the help.
 

boscoe99

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If you don't have a DVA adapter it is pretty easy to convert RMS voltage (what you see on your multi-meter) to peak voltage. Just some simple math.
 

boscoe99

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I cant remember if i unplugged the 3rd wire from the lighting coil when I tested but i will check again and yes i do believe it was shorting to ground i will check that again though. thank you for the info.
What third wire? There are only two wires coming from the lighting coil.

Perhaps you are speaking of the one green wire that is jumpered so as to provide the tachometer its reference signal.
 

doh13

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What third wire? There are only two wires coming from the lighting coil.

Perhaps you are speaking of the one green wire that is jumpered so as to provide the tachometer its reference signal.
Yea that is the one i was talking about thanks for the info .
If you don't have a DVA adapter it is pretty easy to convert RMS voltage (what you see on your multi-meter) to peak voltage. Just some simple math.
I am interested in the math , I get about 2.5v Ac on the multimeter with the motor turning over and 4v with the motor idling , when I check the ohms of the green lighting coil to the ground on the motor it shows a short so am i safe saying the lighting coil is bad?
 

boscoe99

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You are so far off I would guess that it is the lighting coil. D

Did you measure it for ohms? Did you measure it to make sure it was not connected to the block?
 

doh13

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You are so far off I would guess that it is the lighting coil. D

Did you measure it for ohms? Did you measure it to make sure it was not connected to the block?
I just checked the green lighting coil leads and the side with the connector for the RPM signal had approx 8v at 2k-2500 rpms and the other wire only had 2.5-3v at the same rpms i am assuming both leads should have the same voltage eh? Also when trying each of the green coil leads on my multimeter to ground its a short ( 0 ohms) should i put the multimeter on both green wires to get an ohms reading or putting the lead from green to ground the correct way?
 

boscoe99

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Set your meter on AC volts and put one probe on one green wire and the other probe on the other green wire.

It is good that you are reading 0 ohms from either of the two leads to ground.
 

99yam40

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Set your meter on AC volts and put one probe on one green wire and the other probe on the other green wire.

It is good that you are reading 0 ohms from either of the two leads to ground.
Not sure on this 0 ohms reading.
when I put a meter on a shorted connection (meter leads touching each other) it reads 000.4 ohms (meter leads resistance)
when meter leads are not touching each other (open circuit) it reads OL

I guess it depends on what you call Zero ohm reading
 

doh13

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Set your meter on AC volts and put one probe on one green wire and the other probe on the other green wire.

It is good that you are reading 0 ohms from either of the two leads to ground.
checked again and its 9v ac at 2k rpm approx 6-7v at idle
 

boscoe99

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Not sure on this 0 ohms reading.
when I put a meter on a shorted connection (meter leads touching each other) it reads 000.4 ohms (meter leads resistance)
when meter leads are not touching each other (open circuit) it reads OL

I guess it depends on what you call Zero ohm reading
Any internal resistance within the meter and the probes should be taken into account. But perhaps using the continuity function of the meter might be a better choice.
 

99yam40

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so are you saying he should be reading zero ohms from each green wire to the block?
I thought that would mean a dead short to ground, not even going thru part of a coil
and that does not seem right to me.
 

boscoe99

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Maybe I said it poorly. I am saying that there should be no electrical connection between any lighting coil wire and the block.
 
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