1994 135 hp black max V6 Battery Charging System Troubleshooting 40 AMP

[kramerpage]

I do not have rising battery voltage when the motor is at 1000 rpm and above.
I believe my first step is to check wire integrity from battery + to starter solenoid. From there to the pair of red wires to each voltage regulator. The pair of yellow wires going to the stator. Just to look for corrosion. open worn wires and what have you. Oh also grounds on the regulators.

If all is well I will go to check the regulators per the shop manual. which leads me to MY QUESTION.

What if only one regulator is found to be bad? So does each regulator have the ability to distribute 20 amps each to the battery as needed?

Thanks

 

[Texasmark]

Regulators usually are reverse blocked such that if in parallel, the one having the lowest voltage will not be harmed by the higher one pumping current into it from the output.....blocking diode. If the output of both regulators aren't shorted to ground then there is no reason one can't suffice at half the capacity. With two pumping one load, the higher voltage will produce the most current, so there will be inherent differences in who is sharing how much of the load.

 

[Chris1956]

On that dual VR system, each VR can supply up to 20A to charge the battery. So you should see charging if at least one VR is good. You might test the bad VR to make sure it is not shorted to ground.

Look on the circuit boards for burn marks. That is a giveaway....​

 

[kramerpage]

Here is a pic of the two regulators. As you can see the yellow conductors were open from high resistance at the connector which led to overheating and eventually failure.

 

[kramerpage]

So I warmed up the VRs with a hair dryer slightly and performed the diode test. Both VRs passed this test. Now to test the stator.



Voltage Regulator Test

Using Digital Meter Test Leads To-
Diode Check: Con- nect NEGATIVE (?)
meter lead to RED regulator lead in connector. Connect POSITIVE (+) test
lead to either YEL- LOW regulator lead. Results #1 was .427 #2 .431

Diode Check: Con- nect NEGATIVE (?)
meter lead to either YELLOW regulator lead. Connect POS- ITIVE (+) ohm lead to RED regulator lead
in connector. Results Both were OL

SCR Checks: Con- nect NEGATIVE (?)
meter lead to regu- lator case. Connect POSITIVE (+) meter lead to either YEL- LOW regulator lead.
Tachometer Circuit Check: Not measur- able with digital meter Results Both were OL

 

[Texasmark]

Let's back the truck up. What have you been running that's electrical? If no heavy loads, then 22 years of corrosion have taken their toll. why don't you cut the connectors off, and strip and twist the wires together to complete the circuit like it was with the connectors. Crank the engine and test your voltage. If ok, get you some new bayonets or just solder what you have and cover with electrical tape. Bad connections are a runaway situation. As they degrade they form resistive elements which get hot with current passing through them. That process over time just keeps getting worse till you have a catastrophic failure.

I don't see your rectifiers or regulators being damaged by what I see if that is the root cause of your loss of charging ability. However if you were running a couple of boom boom boxes and night lights and an Air Conditioner and Microwave and and and.....then you may have burned up your regulators which caused the yellow stator leads to burn.

That's the way it looks from here.

 

[kramerpage]

Truck has flat tire Tex... thanks for your help. This boat is a new purchase. I call it a SLUG...numerous problems since the previous owner didn't take care of her. I have 3m bullet shrink connectors on hand. Once I saw Thierry condition I figured I'd pull them so I could bench test them. The boat is in the water so it's hard on my old back. I am new to working on outboard motors and slowly learning these things.

 

[kramerpage]

I read the voltage on the two yellow conductors from the stator while the motor was running and got 21 to 22 VAC. According to the shop manual thats within spec so the stator is good. Yeah

 

[Texasmark]

I read the voltage on the two yellow conductors from the stator while the motor was running and got 21 to 22 VAC. According to the shop manual thats within spec so the stator is good. Yeah

Phew.....passed that test.......moving right along. Grin

 

[kramerpage]

Yes i did the happy dance then looked around to see if anyone at the marina was watching....lol

 

[Chris1956]

I have same motor, and some years ago I replaced both VRs with new CDI brand units. When I test the DC voltage it kept changing a few volts, say from 15VDC to 12VDC. Not sure why, as I expected VRs to well, Regulate!

​I do not have any issues with battery charging or battery life, so Ihaven't worried about it. I would be interested in what you observe.

 

[kramerpage]

I installed to new Mercury voltage regulators. They were New Old Stock. The output voltage is 12.9 to 14.9. The voltage on a digital meter constantly goes up and down as you describe.

 

[kramerpage]

Strangely enough by the way the motor with the bad bad vrs runs better Stronger with a much smoother idle. Strange.