rectifier johnston 135 1975

[flips]

Hi guys<br />can you tell me what volts the rectifer should be putting out. Tried new tacho does not work it points back to zero when power is on but does not work with revs, this tacho had been opened in shop which makes me think it could have been a change over unit. The old tacho that came with motor reads up to 1300 rpm but motor is doing much higher when reved changed settings on back just get lower reading ,Pulled old tacho apart and found big resitor very black this makes me think rectifier is bad, Old tacho was 2 wire job red to grey wire and black to ground in control box,<br />new tacho .. send to grey wire, power to bat + or switch, ground to -. Can only think of rectifier gone bad am i on the right track<br />Thanks Flips

 

[flips]

Re: rectifier johnston 135 1975

just tried volt/ohmmeter idle about 2-3 volts<br />2000 rpm ? rise to 4-5 volts quick rev didnt change much not game to rev to hard on muffs readings taken from wires to tacho out of control box. readings from motor on rectifer<br />very jumpy looks like 18 - 19 volts is this right.

 

[flips]

Re: rectifier johnston 135 1975

just tried another tacho does the same thing no movement on dial motor runs fine going to run wires back to motor on another loom set up and see what happens any info would be greatful.

 

[Barnacle_Bill]

Re: rectifier johnston 135 1975

Your rectifier is shot!

 

[ddaigle]

Re: rectifier johnston 135 1975

What is your voltage at the battery while engine is off and then while running? Some of these old engines dont have regulators and will put out 17 -18 volts. Mine does, but according to experts the amps are so low that it doesnt matter. So your rectifier may be good. You have to have the right tach for that motor, not just any tach will work.

 

[flips]

Re: rectifier johnston 135 1975

Thanks <br />IBNFSHN & ddaigle<br />Voltage at battery off is 13.7 volts running is<br />17- 21.4 volts at idle.<br />when i stoped motor battery went back to 13.1

 

[flips]

Re: rectifier johnston 135 1975

bump

 

[chuckz]

Re: rectifier johnston 135 1975

That sounds like the rectifier is OK, unless you're measuring AC voltage. The tach senses the RPM from the AC side of the rectifier. Disconnect the DC side and see if the tach works. If it does, the rectifier is probably shorted.

 

[flips]

Re: rectifier johnston 135 1975

L.I Chuck thankyou so much i just disconneted<br />yellow&grey wire to retifier which ithink is dc<br />and wired up direct to motor not thur control box<br />and it works now to order new recitifer thank you and all others for your help

 

[Terry H]

Re: rectifier johnston 135 1975

Glad you found the prolem...You did most of the work on that one flips...if you need more help you know we are here for ya...just a thought