Testing a modern Regulator/Rectifier

I recently purchased from AO Services a Reg/Rec for my 72 Combat on which I have just installed a brand new Lucas wiring loom plus a modern battery condition analyser. Sadly the battery is not being charged. I have tested the diodes on the Reg/Rec with unexpected results see below:

Multimeter Connection Reg/Rec connection Yellow 1 Yellow 2
Neg Black -2.903v -0.304v
Neg Red 0.46v 0.459v
Pos Black -2.449v -2.906v
Pos Red -0.007v -0.006v

I was expecting 2 of the 4 combinations to show zero (or very close to zero) volts passing the diode. And the other 2 combinations having very similar voltage passing. As you can see above, one combination has almost no voltage passing (Positive multimeter, red Regulator wire connection. One combination as similar voltage passing (-2.5-2.9v - Positive multimeter setting, Black wire connected on Regulator).

The other 2 combinations are a concern.

This is a brand new unit. Bike has an RM19 alternator (2 wire output). These 2 wires go to the 2 yellow wires on the Reg/Rec. The red wire goes to battery positive, the black wire to battery neg..

Any thoughts? Is the unit faulty?????

I'm not clear what you are measuring. The usual way to check charging system is to run the engine and first check you have an AC voltage between the two yellow wires and then check output from regulator between red and black. You can then form an opinion if it's an alternator or regulator problem.

Ian

Nortoniggy said:

I'm not clear what you are measuring. The usual way to check charging system is to run the engine and first check you have an AC voltage between the two yellow wires and then check output from regulator between red and black. You can then form an opinion if it's an alternator or regulator problem.

Ian

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I was using the diode check function on my multimeter to try to determine if the new Reg/Rec was faulty.

Are you sure the battery is not being charged? Is this conclusion based on the installed battery checker? If so, use a multimeter to check the DC voltage at the battery with the engine off and then again with the engine running at 1500 RPM. If the second reading is not noticeably higher than the first, do as Ian suggested.

It is not clear to me exactly how you tested these diodes. Using the check diode function you should be measuring each diode individually, first ensuring there is no voltage present in the system when making the diode checks. IF using the diode check position on a DMM, it should show some voltage, typically around .6v but that can vary a bit, in one direction, and, reversing the leads, show OL (an open circuit) in the other direction on each diode.

Christopher Armstrong said:

I was using the diode check function on my multimeter to try to determine if the new Reg/Rec was faulty.

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Ah, well the theory is good but without knowing the internal structure of the Reg/Rec it's imposiible to know what to expect. It won't just be a simple bridge rectifier. Obviously a dead short would indicate a problem but that's about it. Al' Os' is a very helpful guy so why not ask him for some advice?

First check is to test the AC voltage generated by the RM19 in isolation - should get up to 30v AC

Yes, checking the regulator with the diode function will tell nothing. Measure the AC input to the regulator or better yet without the regulator at around 2Krpm. If that's around 30V then test the output of the regulator red/black or whatever it uses for DC volts without the battery. Then hook up the battery and if it's working you should get somewhere around 13-15VDC on the battery unless the battery is shot. Others say the same. You can get exotic with measuring DC amps and all, but save that for later.

I second Nortoniggy's suggestion i have found Al Osborn to be very good to deal with, i would email him direct if there is any doubt.

Test per DogT method. Most likely your regulator, being new, is good. The fault is therefore in the loom connections.

Check your ground (earth) connections. Many electrical problems are caused by poor grounds.

Slick

Yes, ground issues are very hard to trace unless you really have a lot of experience with the voltmeter and what the readings mean. It can really throw you off, even with experience.