Another charging system problem

From the threads recently charging system problems seem to be the latest rage. Here’s mine.

My sons 1978 KZ1000A2A has low charging system output. I don’t think it should affect the charging output but he’s running a Dyna-S ignition with Accel coils with the coil repower mod.

With the headlight off, system voltage will slowly build to 13.25. Headlight on, system voltage runs around 12.6 to 12.8. Stator output is good 36 volts AC at idle and 58 volts AC at 4000 rpm. (Voltages checked at the stator and at the connection to the rectifier.) Rectifier passes test and doesn’t show any shorted diodes. Unplugging the regulator has no effect on the system. If I read the wiring schematic correctly, the regulator, uses the sense line (brown wire) to read system voltage and shunts (if that’s the right word) the stators AC output to the rectifier to control the charging voltage. I’ve pulled the side cover and checked the wires from the stator back to the electrical panel. I’ve checked all the connections at the panels electrical connectors, they show clean connections. The battery sense wire (brown wire) has a clean path and shows full battery voltage. I cleaned and tightened all the rest of the connections, checked and haven’t found any bad wires, and everything appears to be in decent shape with no excessive voltage drops. The resistance level between the engine block and battery negative was a little high (7 to 9 ohms) we added an additional ground wire to the engine block and have gotten the resistance down between 3 and 4 ohms. I have an extra voltage regulator and rectifier and have tried them both, to no avail. I think I also have a spare stator to try next. One thing I did notice was that if you hook up and monitor the stators AC output, as soon as you hook up the rectifier, the stators AC voltage drops to 11.8 volts AC, with or without the regulator hooked up.

I missing something here, but I don’t know what.
Anyone have any additional ideas before I change out the stator and its wiring?

Thanks in advance for your input.

The AC voltage on the stator wires will always be pretty low. 11.8v is not abnormal there. Depending on circumstances, it can go way down to 6 or 7 volts and up to 12 or 13v (AC).

I'm not sure what's wrong with your bike, but just for your information, the Dyna S ignition uses double the power of the stock ignition. With Accel 3.0 ohm coils, it will use even more. At 13v, the stock uses about 3.25 amps. At 13v the Dyna S with Accel coils will use about 8.7 amps. (This is at low RPMs.)

What is the voltage on the white (maybe red or red/white) coming out of the rectifier, using the black rectifier wire as the negative? If it is higher than that of the battery (measured at the battery terminals), then you probably have some bad connections. If they're about the same, then the alternator (and/or wiring) may be weak and the Dyna S is just enough to put the charging system into a deficit.

Post edited by: loudhvx, at: 2007/07/19 22:47

John, The info you are provided is curious because it sounds like everything is healthy except for the total output of the regulator. I think the wiring itself on the bike might be the cause... The brown sense wire comes via a very circuitous path... Perhaps you could unhook the red wire on the tail light during a test and connect it to the brown sense input to the regulator. It is a switched 12VDC DIRECTLY off the tail light running lamp... doesn't go through the kill switch or a bunch of the connectors the brown does and doesn't perform all the electrical feeds the brown does... horn, blinkers, etc. See if it makes a difference on the output of the regulator at higher rpms to connect the red to the brown in. Just a thought.

Losing voltage on the sense line causes the voltage at the battery to be too high, not too low. But I agree he may be losing power through some wiring.

stator seems to have low AC output to me
I like to do a ohm check and insulation breakdown test first before a unloaded AC potential test at full hot running temperature



unloaded AC I like to see a top near 70~80 ac volts at higher revs 4000 + approx.
58 says to me that there is a bit of dynamic insulation breakdown happening and the stator is getting near borderline.

not bad yet but it is summertime and the old varnish between windings is getting thin and there is less output for the system to get converted to dc.

A big thanks to all you guys for your input.

I checked a little futher. The Dyna-S and coils are drawing just a shade over 5 amps at idle (@ 12.5 battery voltage). The rest of the system circuits are drawing right at 6 amps. The amp probe around the positive wire from the rectifier to the battery/system connection showed the rectifier running at 12 amps.

Checking the rectifier voltage, with the rectifier positive still hooked to the battery/system feed, voltage was right at battery voltage. With the rectifier positive feed disconnected from the system the rectifier voltage jumps to 40 volts DC. There was also a fairly impressive arc when connecting and disconnecting the rectifier system feed with the engine running.

The brown voltage sense wire to the regulator has no effect on the charging system voltage at all. It can be connected or disconnected and the system voltage remains the same. I tried a new route on the sense line, I pulled it from the connector and routed it directly to the battery. This had no effect on the system charging voltage.

I'm thinking that the charging system may be ok (albeit running at full output)and that we've got something else (short, voltage bleed or something) pulling the system voltage down. (Although removing the fuses to the lighting system has no effect on the system voltage.) When my son got this bike it had a bunch of cobbled up wiring on the front where it had a fairing on it at one time. I know he spent some time cleaning up the hack, twist, and tape mess. I think my next plan is to go back through that wiring mess and then start pulling circuits out of the system and see if at some point the system voltage increases.

Thanks again for your assistance.

A big thanks to all you guys for your input.

I checked a little futher. The Dyna-S and coils are drawing just a shade over 5 amps at idle (@ 12.5 battery voltage). The rest of the system circuits are drawing right at 6 amps. The amp probe around the positive wire from the rectifier to the battery/system connection showed the rectifier running at 12 amps.

Checking the rectifier voltage, with the rectifier positive still hooked to the battery/system feed, voltage was right at battery voltage. With the rectifier positive feed disconnected from the system the rectifier voltage jumps to 40 volts DC. There was also a fairly impressive arc when connecting and disconnecting the rectifier system feed with the engine running.

The brown voltage sense wire to the regulator has no effect on the charging system voltage at all. It can be connected or disconnected and the system voltage remains the same. I tried a new route on the sense line, I pulled it from the connector and routed it directly to the battery. This had no effect on the system charging voltage.

I'm thinking that the charging system may be ok (albeit running at full output)and that we've got something else (short, voltage bleed or something) pulling the system voltage down. (Although removing the fuses to the lighting system has no effect on the system voltage.) When my son got this bike it had a bunch of cobbled up wiring on the front where it had a fairing on it at one time. I know he spent some time cleaning up the hack, twist, and tape mess. I think my next plan is to go back through that wiring mess and then start pulling circuits out of the system and see if at some point the system voltage increases.

Thanks again for your assistance.