Tachometer Voltage Regulator/Rectifier Issue

[gbc_redfisher]

My Tachometer is not working at all.....

I know this has been done before...but I want to make sure i tested the Tachometer and both of my Voltage Regulators/Rectifiers before i go out and buy 2 of them. Here are some specs:

1999 Mercury 150hp XR6 Carb Engine
2 ea Regulators/Rectifiers - Mercury part # 854515

Each Regulator has (2) Red wires (2) Yellow Wires and (1) Grey Wire.

I tried out a new Tachometer first....still nothing...needle didn't move. I tried swapping the Grey (Sending) wire from the top Regulator to the bottom...and no change.

I disconnected all the Red/Yellow/Grey wires on both Regulators...with Ohm meter blk lead to ground...took red lead touched each wire individually one at a time and got a reading..ok

Reversed leads....red lead to ground....took blk lead and touched each wire individually one at a time and still got the same readings...not good?

To me, if I read what others wrote on here before...that tells me that both of my Regulators are bad.

Thats pretty much all i have done now....So, could someone confirm if I am correct in assuming that I need (2) new Regulators.

Thanks!

 

[CharlieB]

Re: Tachometer Voltage Regulator/Rectifier Issue

Disconnect all wires from the regulators, Ohm's test each Yellow to red, then reverse meter leads and retest both Yellow to red again. You should have continuity one direction only, nothing when the leads are reversed.

You should DVA test the yellow stator leads to ensure the charging coils of the stator are good.

 

[gbc_redfisher]

Re: Tachometer Voltage Regulator/Rectifier Issue

What if you dont have a DVA multimeter. Is there a way of Testing the Stator with a regular Multimeter?

 

[CharlieB]

Re: Tachometer Voltage Regulator/Rectifier Issue

Ohm's test of alternator/generator coils can often be misleading, a broken winding can Ohm within spec, but once a load is placed on the system the connection fails.

Ohm specs are listed in the service manual and in the CDIElectronics.com Ignition Troubleshooting Guide available for free download at their website.

A DVA Adaptor can be built quite cheaply, search these forums for the schematic and parts list. Basically it is a diode, capacitor, and resister. It places a measured load on the stator while charging the cap, which produces a very reliable reading from your volt meter.

 

[gbc_redfisher]

Re: Tachometer Voltage Regulator/Rectifier Issue

Thanks CharileB! I will look into making a DVA adapter and troubleshoot some more before I go out and purchase some Regulators.

Thanks again!
~Greg

 

[j_martin]

Re: Tachometer Voltage Regulator/Rectifier Issue

You can test this out without a DVA.

Basic theory simplified. There are two windings in the stator, independent from each other, each connected with 2 yellow wires. The two wires have to both go to the same regulator. Each regulator then operates completely independently from the other one.

Disconnect all yellow and red wires.

With engine idling, test the AC voltage on each pair of yellow wires. It should be about 15V per 1000 rpm. Voltage follows rpm all the way up.

That good, connect the yellows and reds to one regulator. With a DC voltmeter on the battery, check to see if it is charging when it is running. You would expect about 12.4V before you start the engine, a big dive while starting, and 13V or more when running, regulated to about 14V max. Check each regulator independently.

It is not unusual for both regulators to fail. One gives up the ghost, and the full load on the other one soon does it in.

The clear (yellow with age) potted regulators are junk from factory. The black ones are a bit better. CDI's are the best.

A common mode of failure is for the yellow bullet connectors to overheat, and that overheat going down the wires into the regulator, stressing it. I would replace those connectors with soldered and heat shrinked splices.

If the regulators are both working, you have something else wrong with the tach.

hope it helps
john

 

[gbc_redfisher]

Re: Tachometer Voltage Regulator/Rectifier Issue

Ok...J_Martin:
I will disconnect all the yellow and red wires again. Idle the engine and check the yellow wires coming from the Stator for 15v ac @ 1000rpm.

Previously, before ever posting my problem, I did check one of my batteries to see if it was charging and it was getting 13v while the motor was running. I have heard that the Voltage Regulators can be bad and still charge the batteries. That's why alot of people recommend Ohm testing the VR's, which I did up above. I was orginally asking if the Ohm test that I performed, as described above, was legitimate and confirms my belief that both of my VR's are bad.

One thing to note, something you pointed out. I did notice the clear connector plugs on some of the Yellow cables looked burnt and melted. I was thinking that if the VR's were bad, it may have been due to overheating.

So, J_Martin - to sum it up, if I am getting 15v AC on the yellow stator wires, I could safely assume the Stator is Good?
Also, could you read through my original post and see how I tested the VR's (ohm tested) and tell me what you think?

On DVA's... I am thinking of making one...but I read that if you are just testing the Stator....if you Multiply 1.41 to your reading...that its the same as using a DVA. Just a thought.

Thanks!
~Greg

 

[sschefer]

Re: Tachometer Voltage Regulator/Rectifier Issue

Dude, make this simple, get a 12vdc test light for 6.00 from Autozone. Start the motor and see if the light comes on when you connect the clip to ground and stick the prob in the connector for the fatter of the two red wires on each rectifer/regulator.

If the light comes on steady and bright the the stator is fine and your rectifier/regultor(s) are probably fine. The problem is with your tach still. Make sure it's a tach designed for outboard marine engines with a variable pulse switch and make sure that the ground it is connected correctly. Test it by manually hooking it up to the motor with clean wiring. If it works then the problem is probably in your harness.

Unlike a automotive engine, the tach for Merc outboards works off the charging circuit not the ignition circuit. Confusing yes, but that's how it works.

 

[j_martin]

Re: Tachometer Voltage Regulator/Rectifier Issue

There probably shouldn't be any reverse continuity to ground on the reds, or the battery would bleed down, but I do know they have a fairly heavy output filter capacitor in them and will draw a spark when connected. (normal) If you tested with a fairly sensitive meter, it would look like a low resistance for awhile. At any rate, I would consider the tests not worthwhile.

No, a bad VR won't usually charge a battery.

Do as I say, temporarily replacing the burned connections with wire nuts. If it works, replace the wire nuts with soldered and insulated connections.

If both VR's charge the battery, and the tach won't run off either one, it's the tach that's bad.

If a VR works, and the tachometer doesn't, you can further verify bad wiring to the tach or bad tach by connecting it to each yellow wire along with the VR. One or both should run the tach.

hope it helps
john

 

[sschefer]

Re: Tachometer Voltage Regulator/Rectifier Issue

The clear covers discolor with age, that's normal don't sweat it unless they are melted and stuck to your block.

I don't know why everyone insists on making the simplest circuit on the engine the most difficult to trouble shoot.

If you take that motor to a shop and the mech pulls out a dva and a multimeter you've got a rookie. The first thing a seasoned mechanic is going to do is put a 12v test light on the red and look for a bright light. Then he'll put that same 12v test light on each of the yellows and rev the engine. If it goes from dim to bright you have charging voltage. If all of them do that then the odds are pretty darn good that the stator charging coils are good.

If you have doubts about your tach, just use any of the yellow leads instead of the gray lead. It's going to give you exactly the same signal voltage as the gray. Your tach will either work or it won't. If it doesn't and the yellow leads tested o.k. with the light then it's your tach and not the rect/regulator.

If for some reason you don't believe this then consider this.. We had tachs long before we had regulators on these motors and they all worked fine and still do. We ran them straight off one of the yellow leads on the rectifier and we let the battery regulate the voltage for us. We didn't worry about it because we didn't have fancy stereos or thousands of dollars worth of sensitive electronic fish finders and GPS systems.

It's your motor though so do as you please. I'm going fishing tomorrow what are you doing?

 

[Faztbullet]

Re: Tachometer Voltage Regulator/Rectifier Issue

A test light wont tell if voltage is high or low, and how bright is bright??? Just test it by the CDI testing spec's below:

Bench Test
Diode plate check: Test the forward diodes between the two yellow wires and the red wire. You should get a reading of about 45K (45,000) on one and a high reading on the other. Check the resistance from each of the yellow wires to case ground, you should get a reading of about 56K (56,000) on one and a high reading on the other. The red wire should read about 14K (14,000) ohms to ground.
Tachometer Circuit:
Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms. Gray to red, and gray to the yellow wires should be a high reading, usually in the M range
Troubleshooting Tachometer
1. At 800-1000 RPM, check output on the gray wire, reading should be at least 8 volts with a DVA meter. A low reading usually indicates a bad regulator if the system is charging the battery.
2. Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms

 

[sschefer]

Re: Tachometer Voltage Regulator/Rectifier Issue

A test light wont tell if voltage is high or low, and how bright is bright??? Just test it by the CDI testing spec's below:

Bench Test
Diode plate check: Test the forward diodes between the two yellow wires and the red wire. You should get a reading of about 45K (45,000) on one and a high reading on the other. Check the resistance from each of the yellow wires to case ground, you should get a reading of about 56K (56,000) on one and a high reading on the other. The red wire should read about 14K (14,000) ohms to ground.
Tachometer Circuit:
Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms. Gray to red, and gray to the yellow wires should be a high reading, usually in the M range
Troubleshooting Tachometer
1. At 800-1000 RPM, check output on the gray wire, reading should be at least 8 volts with a DVA meter. A low reading usually indicates a bad regulator if the system is charging the battery.
2. Check the resistance between the gray wire and engine ground. You should read above 100K (100,000) ohms

Go back to the original post.. The problem was that the tach was not working. Being this far of track is a problem that's been induced by over teching a very simple problem.

How bright is bright.. I don't think that's too hard to figure out.

 

[Faztbullet]

Re: Tachometer Voltage Regulator/Rectifier Issue

Troubleshooting Tachometer
1. At 800-1000 RPM, check output on the gray wire, reading should be at least 8 volts with a DVA meter.

Thats not going to be to "bright" on a 12v bulb....

If it doesn't and the yellow leads tested o.k. with the light then it's your tach and not the rect/regulator.

Nope...Wrong as the tach is seperate circuit in rect/reg so rect/reg could be good and tach side of it bad..

 

[sschefer]

Re: Tachometer Voltage Regulator/Rectifier Issue

Thats not going to be to "bright" on a 12v bulb....

Never said to check it on the gray.

Nope...Wrong as the tach is seperate circuit in rect/reg so rect/reg could be good and tach side of it bad..

Don't matter it still gets it's signal from the same place on a V-6 that it has for years. The stator charging coils. If you think there's some sort of electronic magic going on in there, you are mistaken. The gray wire is only there to make it easier for laymen to hook up the rectifier/regulator. Tell them to hook the gray tach wire up to the one of the yellows and they cry because the colors don't match. So, to stop all the crying they simply added a gray wire. It's also before any rectification and regulation.

Go look at a 1989-90 V6 that has a rectifier mounted on the electrical plate and a separate regulator mounted on the top of the block between the heads.

If you look at theschematic for the rectifier you'll see that the tach wire is connected to the same terminal as one of the yellow wires from the stator. Most of these were 16amp systems but it doesn't matter the 40 is just two 20 amp systems anyway. The regulators on those motors didn't really regulate they just didn't allow the voltage to exceed 14v. Newer regulators have two red wires. The fatter one is the output voltage and the smaller one is reading that voltage and sending it back to the regulator circuit so voltage can be increased as current demand increases. It's called a voltage sensing circuit. However all that happens after rectification of the A/C to D/C and the tach requires A/C for it's signal so it is connected directly to one of the yellow wires even though it comes out of the box gray.

If you count the magnets in the flywheel you'll find that the number of magnets corresponds to the pulse setting for the tach. That's why these types of tachs have a pulse setting and not a cylinder setting like is found in an automobile, (although it is somewhat similar).

Now thats enough of the tech stuff. When the light bulb is on the red wire it should glow bright and steady. When it's on the yellow it will start out dimmer and glow brighter as the rpm increases. Thats because it's A/C voltage and you're only getting half the + voltage, (approx 8 volts positive and 8 volts negative peak to peak) on the one leg.

You can sort of relate to it by picturing the way a 24v circuit is made up of two 12 volt batteries in series or why it takes two 1.5 volt batteries to produce the 3 volts needed to operate the mouse for your computer. Like I said, you can kind of relate to but not completely because there is no A/C counterpart in a battery as I described it.

Hopefully that makes some sense as to why a light bulb will tell you 99% of what you need to know to troubleshoot a tach problem. Once you understand it you can see why a simple 12v circuit tester can tell you if its your regulator/rectifer, your stator or your tach in about 15 seconds.

 

[Faztbullet]

Re: Tachometer Voltage Regulator/Rectifier Issue

Don't matter it still gets it's signal from the same place on a V-6 that it has for years. The stator charging coils. If you think there's some sort of electronic magic going on in there, you are mistaken

There is "magic" as its a seperate circuit built into the VR

Go look at a 1989-90 V6 that has a rectifier mounted on the electrical plate and a separate regulator mounted on the top of the block between the heads.
If you look at theschematic for the rectifier you'll see that the tach wire is connected to the same terminal as one of the yellow wires from the stator.

This is a 99 model and uses 2 20 amp VR ,not a 4 bridge with a regulator,works total different as you said it a"voltage sensing circuit".

the tach requires A/C for it's signal so it is connected directly to one of the yellow wires even though it comes out of the box gray.

If that where true you would read no resistance from the grey to one of the yellow wire. Resistance between the gray and engine ground should read above 100K & gray to the yellow wires should be a high reading, usually in the MEG OHM range...

If you count the magnets in the flywheel you'll find that the number of magnets corresponds to the pulse setting for the tach.

I see you remembered..... I am not saying this wont work but its not the correct way to troubleshoot this type system as you cannot see if any voltages are balanced ie: stator.

 

[sschefer]

Re: Tachometer Voltage Regulator/Rectifier Issue

There is "magic" as its a seperate circuit built into the VR

This is a 99 model and uses 2 20 amp VR ,not a 4 bridge with a regulator,works total different as you said it a"voltage sensing circuit".

If that where true you would read no resistance from the grey to one of the yellow wire. Resistance between the gray and engine ground should read above 100K & gray to the yellow wires should be a high reading, usually in the MEG OHM range...
I see you remembered..... I am not saying this wont work but its not the correct way to troubleshoot this type system as you cannot see if any voltages are balanced ie: stator.

Whatever.. I'll let the OP decide what method he want's to use.

 

[gbc_redfisher]

Re: Tachometer Voltage Regulator/Rectifier Issue

I want to Thank everyone for their advice. I will definitely give it all a try and let ya know the outcome.

~Greg

 

[gbc_redfisher]

Re: Tachometer Voltage Regulator/Rectifier Issue

Well, I finally got around to trouble-shooting the problem some more. Now, I believe that my Stator is bad.

The First thing I tried was to use a Test Light on both Red Wires from either Regulator while its fully connected to the Stator and motor running...the Test light did not illuminate.

I disconnected all the Yellow wires (4ea) coming from the Stator to the Regulator. I did cut the connectors off the (2) short Yellow Stator wires and on the regulator - connected them w/ wire nuts.

I tried putting a Test Light on all four yellow wires (one at a time) while the engine was idling and the light would not come on.

I tried to check for ACV on all four yellow wires (one at a time) and the meter would jump up (between 10.8 - 19.0) only for a second then read -1 or nothing.

I also hooked up (2) different Tachs - I used a single yellow wire from the Stator - hooked it up directly to the Sending post on the Tach and hooked a ground up from the Tach to the motor...both Tachs did nothing especially when I rev'd the motor up.

So, is there anything that I may have missed?...and...What do any of you'll think? Any further input is greatly appreciated!

~Greg

 

[j_martin]

Re: Tachometer Voltage Regulator/Rectifier Issue

Well, here's the bad news. You missed it by mile. Good news, maybe the expensive stator isn't bad.

The 4 yellow wires go to 2 independent coils in the stator. Neither is connected to the other, and no part of either one is connected to ground.

You can't measure the output of the stator on the yellow wires except between the 2 wires in each pair. Any wire to ground will be useless. and a wire from one pair to a wire from the other pair will also be useless. Maybe they got mixed up. Sort it out with an ohmmeter or continuity tester.

So, you say, how the heck do you get voltage to ground from coils that are not connected to ground. Answer. There are 4 diodes in the bridge rectifier input circuit in the regulator. 2 of them selectively ground a stator wire, and the other 2 take the positive voltage then present on the other one on into the regulator circuitry.

Also, a yellow wire will not develop a voltage capable of driving a tachometer unless it is correctly connected along with it's mating yellow wire to the ac terminals on a bridge rectifier. (input yellow on a regulator)

I hope you have 2 regulators, and not 4 yellow wires going to one.

This isn't rocket science, but it is elementary electrical theory. If you don't/won't/can't understand it, get some help.

Well, I finally got around to trouble-shooting the problem some more. Now, I believe that my Stator is bad.

The First thing I tried was to use a Test Light on both Red Wires from either Regulator while its fully connected to the Stator and motor running...the Test light did not illuminate.

I disconnected all the Yellow wires (4ea) coming from the Stator to the Regulator. I did cut the connectors off the (2) short Yellow Stator wires and on the regulator - connected them w/ wire nuts.

I tried putting a Test Light on all four yellow wires (one at a time) while the engine was idling and the light would not come on.

I tried to check for ACV on all four yellow wires (one at a time) and the meter would jump up (between 10.8 - 19.0) only for a second then read -1 or nothing.

I also hooked up (2) different Tachs - I used a single yellow wire from the Stator - hooked it up directly to the Sending post on the Tach and hooked a ground up from the Tach to the motor...both Tachs did nothing especially when I rev'd the motor up.

So, is there anything that I may have missed?...and...What do any of you'll think? Any further input is greatly appreciated!

~Greg

 

[gbc_redfisher]

Re: Tachometer Voltage Regulator/Rectifier Issue

Thanks - John

My motor does have (2) Regulators.

I more or less understand what you saying about how the (2) yellow wires work in a bridged Regulator circuit. So, correct me if Im wrong.

The (2) Red wires (on a single regulator) are connected to the Starter Solinoid and the battery (+) is connected there as well. Thus putting (+) voltage (DCV) on both wires.

First, the Rectifier/Regulator has a ACV circuit design and DCV circuit design. The end result...take ACV voltage convert it to DCV to charge the batteries.

Correct me if im wrong.
So, the Stator sends (+) voltage (ACV) to the Regulator which is grounded via set of diodes - then converts ACV to DCV - the converted ACV to DCV is then put on the Regulator Circuit which correspondes with the Red Wires going to the Starter Solinoid and battery.

The grey wire is non converted ACV voltage that provides the Tach with a variable degree of voltage depending upon how fast the motor is throttled. Thus, rendering RPM readings on the Tach dial itself.

I think my confusion comes from previous posts...where someone said, just take one of the yellow wires coming from the Stator and directly hook it up to the Tach....and I do believe you told me that I should be getting 15v (ACV) on both Yellow wires. I know that you'll know what your talking about and I probably just interpret'd it the wrong way. I do truly appreciate everyone's input.

So, now your saying my Stator may be Ok...and again the VR's are most likely bad.