tach/charging problem

[cpr]

My tach stays on zero until you rev engine high then it jumps to about 6000rpms and then back to zero until you rev again.Also when i check volts on battery cold it reads 12.50 or so with engine running at idle it reads about12.60 goes to 12.83 or so when i rev it high.Any thoughts on if it`s the tach or something else? Tach was working prior to me cleaning the cable connections going from engine to battery.thank you for any help or advice p.s it`s a 1985 140 johnson vro disconnected model #j140tlco

 

[Barnacle_Bill]

Re: tach/charging problem

Test your rectifier/regulator according to your manual. If you created any sparks while cleaning the battery cable it is most likely damaged.

 

[cpr]

Re: tach/charging problem

Not sure if i`m doing it right but here`s some of my readings.Set the meter on ohm scale 2000k with red lead to yellow on rectifier/regulator and black lead to ground reading was about 480 and going up higher.Put red lead to yellow/grey wire and black to ground it also read aroung 480 and rising the longer i held it there.Test were done with both wires unhooked from terminal strip.I then tested the stator wires while i had them unhooked from terminal block.With ohm meter set on 2000 touching red lead to yellow and black lead to ground.The screen reads with a l or 1 on the left hand side it reads the same when i touch red to yellow/grey and black lead to ground.Then i set meter to 200 on ohm scale and touched red lead to yellow and black lead to yellow/grey and it read 1.4 which doesn`t match with stator numbers in clymer book but thats as low as my cheap meter goes.Hope some of this makes sense to ya`ll because i just lost myself.Thanks if anyone can decifer any of this.

 

[HighTrim]

Re: tach/charging problem

Disconnect all 3 wires. There is a diode between each yellow wire and red and a diode between each yellow wire and ground. 4 diodes total.
1. Connect your ohmmeter between one yellow and red. You will have either a high or low resistance. Reverse your ohmmeter leads and you will have the opposite resistance. That is to say it should be high one way and low the other.

2. Do the same with the other yellow and red.

3. Do the same with one yellow and ground

4. Do the same with the other yellow and ground.

If it passes all 8 tests the rectifier is good. Otherwise it is toast.

Also, while you are at it, do a resistance test across the two yellow wires from the stator that were connected to the rectifier. Should be a low resistance continuity. Then check from one of those wires to ground. Should be no continuity to ground.

Don't go putting a new rectifier in without cleaning your battery cable terminals at both ends. Don't just look at them and assume--CLEAN them shiny bright!! Dirty or corroded or LOOSE terminals is what blows rectifiers. That and installing the battery backwards, even for a brief instant.

 

[cpr]

Re: tach/charging problem

My engine has the combo regulater/rectifier.It is on top back of engine grey looking filled with epoxy and water cooled i believe.Would this test work on this setup or is it for the type rectifier that used to be on the side of the older johnson evenrude?

 

[Barnacle_Bill]

Re: tach/charging problem

Double check the 2 yellow wires coming from the stator. Neither one should read anything going to ground.