3wire and 4wire rectifier (troubleshoothing chargin circuit)

makak

Recruit
Joined
Oct 5, 2007
Messages
5
Hello all,

My battery is not charging, engine starts and runs A1!

I ordered a rectifier received it and its a 3 wire rectifier.
When open open the engine cover, looks like the rectifier that already in there is a 4 wire square shape one. I double check the part number and it says 3 wire.

It is a 1970 Johnson 85 electric shift motor model # 85ESL70B
The rectifier I order is part # 580795 RECTIFIER & LEAD ASSEMBLY

I had jumped to the conclusion that my rectifier was bad, so i found a good deal and ordered one. When tested my current rectifier it seemed to be ok, I unplugged the leads one by one and made sure the current is one way by testing with an ohm meter. Im not sure if the test i did is correct.


now im assuming if the rectifier is Ok, the next thing is the Fuse? or Stator?

Im very new to boats, this is my first boat, Im trying to learn all this stuff.

thanks for your help!
 

Barnacle_Bill

Admiral
Joined
Feb 8, 2004
Messages
6,469
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

If you are serious about learning your motor you need to get a manual for it. The procedure for testing the rectifier is in it. Your old rectifier probably has a black wire going to it. This is a ground lead. The new rectifier is grounded internally so the black wire is not needed. BTW, if you ever caused a spark anywhere or hooked up your battery backwards, even for a split second, your rectifier is toast and needs to be replaced.
 

makak

Recruit
Joined
Oct 5, 2007
Messages
5
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

If you are serious about learning your motor you need to get a manual for it. The procedure for testing the rectifier is in it. Your old rectifier probably has a black wire going to it. This is a ground lead. The new rectifier is grounded internally so the black wire is not needed. BTW, if you ever caused a spark anywhere or hooked up your battery backwards, even for a split second, your rectifier is toast and needs to be replaced.

thanks for ur reply. Ok so I can use the 3wire one instead.

I never caused a spark but when it happened the engine was off and I had the radio on, i think it happened when i started the engine with the radio on.

i havent touched the cabled battery when it happened it was working ok.

before i go and order a new stator, could a fuse somewhere cause this?

thanks
 

F_R

Supreme Mariner
Joined
Jul 7, 2006
Messages
28,226
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

It is possible to use a bridge diode rectifier from an electronics supply house (Radio Shack). They are way cheaper than the OEM one, and a good fix if you are aware that it can be done. They usually are a square black unit with 4 bare wires coming from it. Is this what your motor has on it?

Anyway, whatever form it has, a bridge rectifier has 4 diodes in it. That includes the OEM and/or the Radio Shack one. You test each diode separately using a ohmmeter or continuity light.

To test the rectifier, you connect your tester to one of the yellow leads and ground. Then you switch the test leads on the same yellow/ground pair. It should pass current in one of the hookups but not the other. That tested one of the 4 diodes.

Test the 2nd of 4 diodes the same way, only between the other yellow lead and ground. Should have the same results.

Test the 3rd of 4 diodes the same way, only by connecting the tester between one of the yellow leads and the red lead. Should have the same results

Test the 4th of 4 diodes the same way only by connecting to the other yellow lead and the red lead. Should have the same results.

Note that you have made 8 hookups. It has to pass all 8 to be good.
 

clemsonfor

Lieutenant Junior Grade
Joined
Sep 19, 2005
Messages
1,011
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

good post on testin rectifier
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

And for a very simple test of the charging system, just measure DC voltage across the battery terminals with a decent DVOM. With the motor fast idling, you should get > 13VDC, ideally ~ 13.5 to 14 VDC. If 12.7 VDC or <, NO CHARGE. Then you get to trouble shoot the wiring, stator and rectifier.
 

dajohnson53

Lieutenant Commander
Joined
Apr 28, 2004
Messages
1,627
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

It is possible to use a bridge diode rectifier from an electronics supply house (Radio Shack). They are way cheaper than the OEM one, and a good fix if you are aware that it can be done. They usually are a square black unit with 4 bare wires coming from it. Is this what your motor has on it?

Anyway, whatever form it has, a bridge rectifier has 4 diodes in it. That includes the OEM and/or the Radio Shack one. You test each diode separately using a ohmmeter or continuity light.

To test the rectifier, you connect your tester to one of the yellow leads and ground. Then you switch the test leads on the same yellow/ground pair. It should pass current in one of the hookups but not the other. That tested one of the 4 diodes.

Test the 2nd of 4 diodes the same way, only between the other yellow lead and ground. Should have the same results.

Test the 3rd of 4 diodes the same way, only by connecting the tester between one of the yellow leads and the red lead. Should have the same results

Test the 4th of 4 diodes the same way only by connecting to the other yellow lead and the red lead. Should have the same results.

Note that you have made 8 hookups. It has to pass all 8 to be good.

Do you know if this will work with the "rectifier/regulator" on my J200TXESM? I have an OEM service manual and it doesn't list tests like this.

Thanks
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

A bridge rectifier is a bridge rectifier ... doesn't make any difference whether it's from Ford, GM or BRP. They all may be tested in the same fashion. F_R's test is fine. I usually approach it differently. I test the battery voltage with motor fast idling. Less than 12.7 VDC says not charging. Then measure AC voltage across the yellows from the stator ... if you don't get 18 to 20 VAC or more, the stator has quit. Otherwise, the rectifier is NG. All of the above assumes all the associated wiring is OK (no shorts, high resistance terminations, etc.)
 

dajohnson53

Lieutenant Commander
Joined
Apr 28, 2004
Messages
1,627
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

A bridge rectifier is a bridge rectifier ... doesn't make any difference whether it's from Ford, GM or BRP. They all may be tested in the same fashion. F_R's test is fine. I usually approach it differently. I test the battery voltage with motor fast idling. Less than 12.7 VDC says not charging. Then measure AC voltage across the yellows from the stator ... if you don't get 18 to 20 VAC or more, the stator has quit. Otherwise, the rectifier is NG. All of the above assumes all the associated wiring is OK (no shorts, high resistance terminations, etc.)

Thanks. I don't have a charging problem at all. When I measure volts across the battery terminals when engine is at fast idle, I get >14 volts. I think it leveled off at something like 14.6 at fast idle. The volt meter on the dash also shows 13+, which is normal. The problem I have is that the tach isn't working. Conventional wisdom given to me is that if the tach doesn't work, but the charging system is working, it's the tach. However, I hook up a new tach (with alligator clips) and it doesn't work. I get voltage at the tach at both the purple ignition wire-ground and also at the gray sender wire-ground. So I'm stumped.

Next step (this evening or tomorrow) is to (a) hook the new tach directly to the gray wire at the rectifier and (b) test all the diodes of the rectifier. I believe I've read somewhere on this forum that the sort of rectifier/regulator on this 200 HP johnson can have a "partially blown" (my words) situation where it will charge OK, but not run the tach.

The only good news is that there is a rectifier/regulator available locally. Bad news, of course, is that it's list price ($260) and obviously I don't just want to throw a part like that at it.
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: 3wire and 4wire rectifier (troubleshoothing chargin circuit)

Test with a known good tach, if possible.
 
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