How to test a rectifier/regulator ?

[csaba]

I have a 1973 Johnson 65HP Outboard and I need to test its rectifier/regulator ? I know that the charging system isn't working but how do I easily check the rectifier/regulator ?

 

[wilde1j]

Re: How to test a rectifier/regulator ?

If you have 18 to 20 VAC at idle from stator to regulator/rectifier AND ALL (+ & -) terminations are clean and tight, wire isn't broken, and still not charging, regulator/rectifier is probably bad. You can confirm that all's well w/ the charging system by measuring across battery terminals at idle ... should get 13.5 to 14 VDC.

 

[sho305]

Re: How to test a rectifier/regulator ?

Seems that the alternator makes AC power you can test for at the wires going to the rectifier, there may be other wires for the ignition system. There may be multiple wires to rectifier and a high & low speed charging loops on some motors; or it may cut in at a specific rpm like my Force that starts at 1000rpm. My old Merc charges all the time and more with more rpm. It will run over 16 volts at 5000 rpm/12.8v at idle. <br /><br />The rectifier converts AC to DC so if you have lots of AC after it & no increase in DC, it is bad. No AC going to it would be bad alternator.<br /><br />I check battery voltage, then start it and see if it goes up. If not rev it a little and see if it works at a fast idle or charges when running faster but not slower as your voltage will rise. If nothing look for AC power, then look for AC before the rectifier. Stay away from ignition and trigger wires so as not to be confused about what is part of the charging system or not.

 

[almost retired again]

Re: How to test a rectifier/regulator ?

Hello CSABA,

 

[almost retired again]

Re: How to test a rectifier/regulator ?

Hello CSABA,<br />I don't believe that the engine you have has a regulated out put, yours I believe has three wires comming out of it. I don't have a manual at home, so take this with a grain of salt.The wires will be colored yello-yellow with a grey stripe and red. The red wire is the output +, the case of the rectifier acts as the negitive side. The yellow, and yellow/grey are the stator output which is AC. The proper way to check it is with an ohmmeter set either on the diod scale, or a low ohms scale. You will be checking the front to back ratio on each of the diods,there are 4 diods in the case that make up the bridge network. So if you hook the 2 meter leads between any 2 leads from the rectifier, or case the meter should read very high in one direction, and zero when the leads are reversed. Keep doing this until all possable combinations are measured. If all of the above steps check out it's a good rectifier, but if any one of the combinations dosn't pass the high-low test you've got a bum rectifier.<br />I hope you can make sense out of all this.<br />Good Luck

 

[sho305]

Re: How to test a rectifier/regulator ?

Yes, that is right. Think of the rectifier as a one-way-valve for the power. The AC alternates its poles, and the rectifier only lets the current pass when it is going in the right direction so there is only DC beyond it. So it will test lots of ohms resistance one way, but let it pass the other way with a very low reading. The two alternator wires are normaly the ends of the coils wrapped in there, multiple coils to generate a smoother flow of AC to better supply DC since only half of it will get through as DC. The other half is going the wrong way and the rectifier stops it.