Rectifier/Regulator Help

Sendero · Nov 20, 2010

I have a 1996 Mercury 200 EFI. My tachometer started to act crazy. It jumps around sometimes and is unreliable. Sometimes it appears to show the right reading, but then sometimes spikes depending on how much power I give it.

Also, my cranking battery is being drained while the boat sits. I disconnect the battery when I put the boat up to keep it from draining. When I reconnect the battery, there are sparks as if the motor is on.

From everything I've read, it appears I have a bad rectifier/regulator(s). I wanted to see what I could do before spending $300 to replace both of them. I realize that is probably the easiest fix, but definitely the most expensive.

In the attached picture, you can see that one of the yellow wire connectors that is connected to the upper rectifier is burned. That rectifier is also the one that the tach is connected to. Could replacing the connector possibly help?

Both rectifier/regulators appear to be the originals with the clear potting. Neither circuit board in either regulator appears damaged or melted like I hear some people have experienced.

I tried ohmmeter tests on both rectifiers. I disconnected all the wires before testing. Both rectifiers had essentially the same results. Three of the tests came back within the proper range, but one didn't. I'm not sure what this tells me, however, because I'm no electrical guru. Here were the results:

Negative to Yellow, Positive to Large Red = 40 (should be between 100-400)
Negative to Large Red, Positive to Yellow = 100K (should be between 40K to infinity)
Negative to Yellow, Positive to Ground = 20K for one 15K for other (should be between 10K to infinity)
Negative to Ground, Positive to Gray = 19K for one 15K for other (should be between 10K to 30K)

Any help would be appreciated. Thanks.

j_martin · Nov 20, 2010

Re: Rectifier/Regulator Help

Sendero said:
I have a 1996 Mercury 200 EFI. My tachometer started to act crazy. It jumps around sometimes and is unreliable. Sometimes it appears to show the right reading, but then sometimes spikes depending on how much power I give it.

Also, my cranking battery is being drained while the boat sits. I disconnect the battery when I put the boat up to keep it from draining. When I reconnect the battery, there are sparks as if the motor is on.

From everything I've read, it appears I have a bad rectifier/regulator(s). I wanted to see what I could do before spending $300 to replace both of them. I realize that is probably the easiest fix, but definitely the most expensive.

In the attached picture, you can see that one of the yellow wire connectors that is connected to the upper rectifier is burned. That rectifier is also the one that the tach is connected to. Could replacing the connector possibly help?

Both rectifier/regulators appear to be the originals with the clear potting. Neither circuit board in either regulator appears damaged or melted like I hear some people have experienced.

I tried ohmmeter tests on both rectifiers. I disconnected all the wires before testing. Both rectifiers had essentially the same results. Three of the tests came back within the proper range, but one didn't. I'm not sure what this tells me, however, because I'm no electrical guru. Here were the results:

Negative to Yellow, Positive to Large Red = 40 (should be between 100-400)
Negative to Large Red, Positive to Yellow = 100K (should be between 40K to infinity)
Negative to Yellow, Positive to Ground = 20K for one 15K for other (should be between 10K to infinity)
Negative to Ground, Positive to Gray = 19K for one 15K for other (should be between 10K to 30K)

Any help would be appreciated. Thanks.

A good regulator will spark a little bit when you connect the battery. There's a capacitor that takes a charge, then quits drawing current. It is normal for them to have a few milliamps leakage.

Disconnect the reds on both regulators. Then hook an ammeter or a small 12 volt bulb in series with the battery cable. It should be essentially 0 amps, or light completely out.

Now connect the reds to one regulator at a time and see if the meter moves or the light glows. If it does, that regulator is bad.

FYI, the tachometer can be connected to either regulator. Also, you can run on one regulator if you don't have a lot of auxiliary electrical load. (lights, electronics, etc) You can test each regulator separately for charging and tachometer operation.

hope it helps
john

Sendero · Nov 21, 2010

Re: Rectifier/Regulator Help

j_martin said:
A good regulator will spark a little bit when you connect the battery. There's a capacitor that takes a charge, then quits drawing current. It is normal for them to have a few milliamps leakage.

Disconnect the reds on both regulators. Then hook an ammeter or a small 12 volt bulb in series with the battery cable. It should be essentially 0 amps, or light completely out.

Now connect the reds to one regulator at a time and see if the meter moves or the light glows. If it does, that regulator is bad.

FYI, the tachometer can be connected to either regulator. Also, you can run on one regulator if you don't have a lot of auxiliary electrical load. (lights, electronics, etc) You can test each regulator separately for charging and tachometer operation.

hope it helps
john

Forgive my stupidity. I understand what you mean in regards to the wires, but I'm not sure I understand what you mean about how to hook up the ammeter. Should one end of the ammeter be connected to the battery cable (I assume it would be at the terminal?) and then the other would be connected to each disconnected red wire one at a time? Then I should connect the reds one regulator at a time, but what is the ammeter connected to on this part?

Sorry, just learning to do this.

I'm just not sure where, exactly, to hook each side of the ammeter to.

j_martin · Nov 21, 2010

Re: Rectifier/Regulator Help

Sendero said:
Forgive my stupidity. I understand what you mean in regards to the wires, but I'm not sure I understand what you mean about how to hook up the ammeter. Should one end of the ammeter be connected to the battery cable (I assume it would be at the terminal?) and then the other would be connected to each disconnected red wire one at a time? Then I should connect the reds one regulator at a time, but what is the ammeter connected to on this part?

Sorry, just learning to do this. I'm just not sure where, exactly, to hook each side of the ammeter to.

Disconnect the positive battery cable. Connect the positive lead of the ammeter to the positive terminal of the battery. Connect the negative lead of the ammeter to the cable.

Sendero · Nov 21, 2010

Re: Rectifier/Regulator Help

Ahhh. Ok. That makes sense. I'll give it a try.

Sendero · Nov 21, 2010

Re: Rectifier/Regulator Help

Ok, I still don't claim to know what I'm doing, but this is what I found:

I disconnected the red wires from both regulators. I used my multimeter and changed the setting to DCA 10m (I assume that's milliamps?). I then attached the negative to the battery cable and the positive to the positive battery terminal. There was no reading.

I then connected the red wires for the top regulator and I got a reading of 3 on the 1-10 scale (I assume that means 3 milliamps?).

I then disconnected the top regulator and connected the red wires for the bottom regulator. Again, I got a reading of 3.

I then connected the red wires for both regulators and got a reading of 6.

Does that mean regulators together are allowing a 6 milliamp flow? Is that significant?

Sendero · Nov 21, 2010

Re: Rectifier/Regulator Help

Ok, I decided to simplify since I really don't know how to use a multimeter. I bought a 6-12 volt light circuit tester which I'm assuming you're refering to. I clipped one end to the battery cable. With all the red wires disconnected on both regulators and when I touch the needle of the tester to the positive terminal, I get no light. When I connect the red wires on either regulator, the light comes on when I touch the tester to the positive battery terminal. Are my regulators bad?

Sendero · Nov 21, 2010

Re: Rectifier/Regulator Help

As I'm waiting for replies, I'm trying to check out other possibilities. I think I may have found another culprit to the draining battery. There are still several unresolved issues with the regulators, namely the tachometer acting screwy, but this is what I found:

There are several other wires connected to the positive terminal on the cranking battery. This is a 1996 boat that I bought a year or so ago. I'm not sure what they all are to, but I figured I'd leave them alone. I decided to use my multimeter to check the amps for the other wires. As I said earlier, I get 6 milliamps (if I'm reading it right) coming from the motor battery cable. There are about 4-5 other wires normally connected to the positive cranking battery terminal. I checked each one using the 10m setting on DCA. All of the other wires showed no needle reading. However, one pegged. I changed the DCA setting to 250m and checked it again. This time it read about 60-70 milliamps. 6 milliamps may not be much, but is 60-70??

I traced the wire to under the console. It turns out that this wire goes to the motor trim gauge. Once I determined that, I decided to see what happens when I connect the wire to the battery. Sure enough, the gauge goes from dead to reading the motor trim level. Why would this gauge be wired to be on all the time? Have I found one of my battery draining culprits?

j_martin · Nov 21, 2010

Re: Rectifier/Regulator Help

Sendero said:
As I'm waiting for replies, I'm trying to check out other possibilities. I think I may have found another culprit to the draining battery. There are still several unresolved issues with the regulators, namely the tachometer acting screwy, but this is what I found:

There are several other wires connected to the positive terminal on the cranking battery. This is a 1996 boat that I bought a year or so ago. I'm not sure what they all are to, but I figured I'd leave them alone. I decided to use my multimeter to check the amps for the other wires. As I said earlier, I get 6 milliamps (if I'm reading it right) coming from the motor battery cable. There are about 4-5 other wires normally connected to the positive cranking battery terminal. I checked each one using the 10m setting on DCA. All of the other wires showed no needle reading. However, one pegged. I changed the DCA setting to 250m and checked it again. This time it read about 60-70 milliamps. 6 milliamps may not be much, but is 60-70??

I traced the wire to under the console. It turns out that this wire goes to the motor trim gauge. Once I determined that, I decided to see what happens when I connect the wire to the battery. Sure enough, the gauge goes from dead to reading the motor trim level. Why would this gauge be wired to be on all the time? Have I found one of my battery draining culprits?

Man, it's Sunday. I've been napping.

The power to the trim gauge should not come directly from the battery. It should come from the purple instrument supply wire from the control harness. That's what's draining your battery.

6 ma leakage is not significant. It'll theoretically drain your battery in about 4200 hours, or 6 months. 60 ma, however, is significant, as it would drain the battery in about 3 weeks. (less, of course, if the battery is old.)

OK, now that you've identified that leak, get back to the voltage regulators.

First thing, unbolt them and clean them up so they make good contact with the mounting plate. The clear potted ones are grounded through the frame.

Then connect them up one at a time, put your voltmeter on the battery, notice the voltage with key off (should be 12.5 or so), start it up, go to fast idle, 1500 or so, and it should climb to 13.5 if the battery needs a charge, to as high as 15 if it's topped off. Do that with each regulator.

Assuming both work OK, connect the tachometer to each one and not if it works OK. Leave it on whichever one works. If it works on neither, hook it up to one of the yellows connected to either regulator. (use an insulation piercing test clip, and repair the wound afterwords.) If it still doesn't work, the tachometer is bad. (you think?

)

hope it helps
john

Sendero · Nov 21, 2010

Re: Rectifier/Regulator Help

Thanks John. I'll check it out as soon as I can get on the water. I appreciate the response. At least I feel I'm sorta on the right track now.

199675hpforce · Nov 21, 2010

Re: Rectifier/Regulator Help

Ok ive owned serveral boats and every time get this, turn the dial on your tach and return it back to same position. Fixed mine every time?

Rectifier/Regulator Help

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