1988 Jsn 150 - Charging system

[winfieldh]

Hello,
How would I check the charging system of the above motor? I have no volt gauge on the dash, I have put a multimeter on the battery before and during engine running, but don't see any appreciable difference. Somewhere I have read how to check this system at rectifier/regulator, but can't seem to find it. Any guidance much appreciated.
Thank you,
Winfield

 

[Joe Reeves]

Re: 1988 Jsn 150 - Charging system

If you have a tachometer, and it functions normally, the charging system is operational. The tachometer operates off of the charging system's 6 pulse setup. If no tachometer, redo the test you seem to have already done as follows.

Have a voltmeter connected across the battery terminals set to read 12 volts. Observe the reading.

Start and run the engine. Observe he reading. The voltage should have increased somewhat UNLESS the battery is fully charged already.

If there is no voltage increase OR if the battery voltage appears to decrease with starter usage, electrical equipment, etc, the usual cause is a faulty regulator/rectifier assy.

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

Ah...that might be what I read. There is a tach and it is functioning properly. Just had me puzzled since I couldn't see any movement on the meter. Thanks so much for the quick reply.
W

 

[boobie]

Re: 1988 Jsn 150 - Charging system

If the tach is working properly you could have a bad meter.

 

[Barnacle_Bill]

Re: 1988 Jsn 150 - Charging system

The rectifier can be bad and the tach still work. It all depends on which diode blows and how it blows. Shorts out or opens.

 

[wilde1j]

Re: 1988 Jsn 150 - Charging system

If you get no voltage increase running/stopped, then you're not charging. Even with a fully charged battery, you should see 13 to 13.5 vdc running. A fully charged battery in most of the US will read ~ 12.7 to 12.8 vdc static (not running). The other possibility as pointed out by Boobie is a bad meter.

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

How can I check rectifier?

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

After reading the "Why doesn't my tach work" thread (very similar engine year/model), I'm a little nervous. From that thread to check stator:

"With not running engine:
Measure resistance (Ohm) between the two yellow - you should have resistance.
Measure resistance between yellow and ground - you should have open circuit (no resistance reading)
If any of the above fails, you have a defective stator."

I have just checked resistance between yellows, there is none (same reading as touching red/black probes together).
Checking between each yellow and ground, there is none (although not as easily detected, meter still shows little or no resistance).

Engine and tach run fine, but my initial concern was with charging so do I infer from this, stator=bad? Would that not have other signs as well?

Thanks.

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

Just did another check with engine running.
I get 25VAC across yellows
I also get 25VAC crossing ea yellow to ground
Rot Roooooowwww???? What does this insinuate?

 

[wilde1j]

Re: 1988 Jsn 150 - Charging system

The stator is OK. Likely bad R/R.

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

Thank You. I will proceed the R/R route.

 

[Fed]

Re: 1988 Jsn 150 - Charging system

Just had me puzzled since I couldn't see any movement on the meter.

So you had your meter set on DC Volts and put it across the battery, got a reading then started your motor and the reading remained the same?
Wouldn't want to see you do any unnecessary work.

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

Fed --
Yes. I saw no difference between running and not running on the battery terminals (dc), but the tach works which is what got me curious. Then I did the test on the yellow terminals from R/R/Stator and the results are as posted. Still point to the R/R?

 

[Fed]

Re: 1988 Jsn 150 - Charging system

If your battery is down on charge it's likely you won't see any appreciable difference until the battery comes up.
If that was the case try it again with a fully charged battery.

There is a load test but it requires a 40A ammeter.

BTW, when you're checking the stator resistances you need to do it with the stator wires disconnected.

I have just checked resistance between yellows, there is none (same reading as touching red/black probes together).

That reading should be very close to zero, my manual shows 0.17 Ohms for a 150HP with a 35A stator. (Same as shorting the meter leads)

Checking between each yellow and ground, there is none (although not as easily detected, meter still shows little or no resistance).

That reading should be close to open circuit. (Same as leaving the meter leads apart)

 

[winfieldh]

Re: 1988 Jsn 150 - Charging system

The previous tests pointed toward a bad rectifier....new one is now on hand, but....

This is a watercooled, 6-bolt unit. The two outboard (port/stb) bolts have snapped off when removing unit. They did have 1/4" sticking up, but looks like there is still 1" of bolt in the block. I have applied heat and oil to one, it has now broken off flush with block. I am leary of the other, but feel it will do the same when attempted. It looks like the bolts are grade-8 into a softer metal block so drilling out will be very challenging to stay on track. I have done the heli-coil thing many moons ago on different application.

What, if any, are my options here? I have 4 good bolts/holes and have new bolts. Any tricks would be much appreciated.

Thank you,
Winfield

Follow up....
2 drill bits and 2 helicoils later, rectifier is installed and everything back together. Will test tomorrow. Cheers.W

 

[Fed]

Re: 1988 Jsn 150 - Charging system

I don't want to rain on your parade but did you put sealing compound on the rectifier bolt threads to stop it happening again and did torque the flywheel to a perfectly clean & dry taper?
Hope it all goes well for you.