Testing a Regulator/Rectifier on a KZ650 ???

Outaline's method is probably the best way (on a 650 like yours) without having to buy a new reg/rec if you have a spare battery around. (The test is slightly different on other bikes)

A battery with a dead cell will still show a higher voltage on it when the charging system is working.

EXACTLY! That is why I asked he test the darn battery before worrying about more complicated tests on other components. His original problem was that the battery didn't hold a charge. Simplest thing, seems to me, would be to test the battery first... I have seen a number of NEW or ALMOST NEW batteries with bad cells.

Don't trust the Clymer procedure for testing regulator/rectifiers. It will tell you nothing, and convince you that it's bad, even when it's not.

I installed a new reg-rec on my bike yesterday. My old one was crap, and was letting too much juice through. The lights got much brighter above 3000 RPM, and I was blowing dash and turn signal bulbs.

I tested the new reg/rec before installation using the same method you're using, and got really stupid readings. I think that the test procedures make assumptions about the voltage output of your multimeter. The new unit is working fine, lights are even, battery is charging, not blowing bulbs, etc., but according to the multimeter it's not passing electricity no matter how I hook up the meter.

Because you asked, the readings I got were infinite resistance with both positive-to-yellow and positive-to-black, on a unit that's been behaving well for me so far. 1978 D1A (SR). I even replaced the battery in my meter, thinking that it was the culprit. I think it's just that newer meters with solid-state components are much more sensitive, and don't put out the same amount of power as the older equipment.

Rectifiers cause a constant voltage drop (1.4V for some common diodes, for instance), as opposed to resistors for which voltage drop depends on current passed. If the meter isn't putting out enough voltage to reach the conductance threshold, it will read infinite (or very high) resistance.

Feel free to PM me if there's any testing you'd like me to do with voltage levels, etc.

wiredgeorge wrote:

EXACTLY! That is why I asked he test the darn battery before worrying about more complicated tests on other components. His original problem was that the battery didn't hold a charge. Simplest thing, seems to me, would be to test the battery first... I have seen a number of NEW or ALMOST NEW batteries with bad cells.

He had higher voltage on the battery when it was not running. A bad cell would show bad running or not. The voltage was lower when running.

Therefore, no need to test battery to know charging system is not working or wiring is bad.

Hydrometers only tell you the condition of the acid and won't indicate other problems. A shorted cell can still have normal acid.

Post edited by: loudhvx, at: 2005/11/11 13:18

GargantuChet is right on.

Disagree... a hydrometer WILL show a dead cell or marginal cell. In fact, they are quite accurate as the specific gravity of the fluid in the cell is a very accurate way of determining if it is any good. My point is, his problem was that the battery was not holding a charge; check the battery FIRST... I give up on this one...

wiredgeorge- I never said the battery wouldn't hold a charge. Read the first question, it says the battery isn't getting a charge, that is why I never tested the battery. The battery holds a charge just fine, however if you repeadely start the bike without charging it obviously the battery will discharge, so maybe that's what you were thinking. Anyway, I found the problem. It was a bad ground at the regulator. I found it open, so I rewired it, fired it up, and instantly had 14V at idle, and like 13.7 at 4K. Thanks for all the replies.

wiredgeorge wrote:

Disagree... a hydrometer WILL show a dead cell or marginal cell. In fact, they are quite accurate as the specific gravity of the fluid in the cell is a very accurate way of determining if it is any good. My point is, his problem was that the battery was not holding a charge; check the battery FIRST... I give up on this one...

His symptoms indicated bad wiring or a bad reg/rec. He was on the right track. The battery was not in question. Maybe you're responding to the wrong thread.

Hydrometers don't always show everything you need to know. When a good cell becomes shorted by a broken plate, the acid will still be good. The acid is out of the electric path. A hydrometer would show the acid to be good, but the cell would be useless to the bike and the battery will be around 10 volts.