722: There's No Such Thing As A Stupid Question, Right?

[Atilathehun99]

Here's the latest issue. Battery checked good, new alternator. The machine doesn't seem to be charging the battery or even able to keep running when at low RPMs. My question is this. Does the charge to the battery travel through the ignition switch (or some other route) and not directly from alternator to the battery? I know the fact that the unit needs to run at high RPMs works against a switch problem but I'm trying to figure this out.

 

[Tazza]

If it's not a 1 wire alternator you will have switched power going to the alternator to energize it.
Ensure the diode is good that is feeding the alternator.
One test you can do to cehck the alternator is to hook it up, start the engine. Get a meter and check the voltage at the battery. get a wire from the +ve battery terminal and brush it over the exciting terminal on the alternator, see if the voltage jumps up.
Most alternators only need power once and from there they self excite till the engine stops. You may need to have the revs up some to get it to start though, but not flat out.

 

[OldMachinist]

If it's not a 1 wire alternator you will have switched power going to the alternator to energize it.
Ensure the diode is good that is feeding the alternator.
One test you can do to cehck the alternator is to hook it up, start the engine. Get a meter and check the voltage at the battery. get a wire from the +ve battery terminal and brush it over the exciting terminal on the alternator, see if the voltage jumps up.
Most alternators only need power once and from there they self excite till the engine stops. You may need to have the revs up some to get it to start though, but not flat out.

Looking at the wiring diagram for the 722 it shows the alternator output goes up to the ignition switch before returning to the large terminal on the starter.
Check the voltage coming out of the alternator at the large terminal with the engine running about 1000-1200 rpm's. If it's higher than the battery voltage then the alternator is working but the juice isn't getting to the battery.
You may have a connection problem in the connector that connects the cab wiring to the engine wiring.

 

[Atilathehun99]

Looking at the wiring diagram for the 722 it shows the alternator output goes up to the ignition switch before returning to the large terminal on the starter.
Check the voltage coming out of the alternator at the large terminal with the engine running about 1000-1200 rpm's. If it's higher than the battery voltage then the alternator is working but the juice isn't getting to the battery.
You may have a connection problem in the connector that connects the cab wiring to the engine wiring.

Thanks much for the replies. I see someone has hardwired the output wire bypassing the plug in connector between the engine harness and harness to the instrument panel. There are two taped connections and one or both of them might be bad. My next step will be to open them up, inspect, and probably replace with connectors.

 

[OldMachinist]

Thanks much for the replies. I see someone has hardwired the output wire bypassing the plug in connector between the engine harness and harness to the instrument panel. There are two taped connections and one or both of them might be bad. My next step will be to open them up, inspect, and probably replace with connectors.

Sounds like you're on the right track. One of my general rules when troubleshooting problems is to start where someone has been before.

 

[Atilathehun99]

Sounds like you're on the right track. One of my general rules when troubleshooting problems is to start where someone has been before.

Checked out the bypass splices and they look good. I opened up the instrument panel to check for possible bad connections and nothing jumped out as bad. However I did notice something that I'm sure has been this way for some time. I have one wire from the harness that isn't connected to anything. Most of the wiring colors are quite faded but this one looks like it could be green and white. I have the wiring schematic that is a reprint of maybe another reprint of maybe another reprint. Bottom line is it's hard to read and I can't figure out what's what. Can anyone send me the schematic which hopefully will be easier to read?

 

[OldMachinist]

Checked out the bypass splices and they look good. I opened up the instrument panel to check for possible bad connections and nothing jumped out as bad. However I did notice something that I'm sure has been this way for some time. I have one wire from the harness that isn't connected to anything. Most of the wiring colors are quite faded but this one looks like it could be green and white. I have the wiring schematic that is a reprint of maybe another reprint of maybe another reprint. Bottom line is it's hard to read and I can't figure out what's what. Can anyone send me the schematic which hopefully will be easier to read?

Need a email address to send it to.

 

[Atilathehun99]

Need a email address to send it to.

Update. A readable wiring schematic was great (thank you Oldmachinist). From that I discovered someone (OK, it was me) had connected the #2 alternator terminal (sensing wire) to the solenoid post that was only energized during start. After correcting that error that BAT post on the alternator now shows 14+ Volts when running where previous it showed only a little above 12 V. I also connected a wire that hadn't been (it was this way when I got the machine) This one was the blue wire from the harness that connects to the solenoid post that's only hot during start. This is the way the wiring schematic shows it should be. When starting the machine would run for a few seconds and die. To me it was acting like it wasn't getting fuel so I clean the carb and replaced the filter. The problem continued so on a whim I disconnected the blue wire to the hot starter post and the machine now runs fine. So I know the blue wire is intended to be a 12 V direct to the coil during starting but I'm confused why with it hooked up it doesn't permit the engine to run. I realize there could be a short in that wire somewhere but would that over ride the normal 9 V power to the coil when running