Lazer Z CT Rectifier Question

[cruzenmike]

My step dad gave me an ExMark that he said was having a hard time holding a charge. He stated that after a couple of cuts (about 2 acres each), the mower would have a hard time starting. He did replace the battery with a 350 CCA unit this past year and it was put on a trickle charger after every use, so the starting issue, for the time being, is no more. When I got the mower I used it a few times, not paying attention to the sticker stating to engage the PTO at half throttle. Me being the stickler I am for running and maintaining equipment per the manufacturer's recommendations, the first time I engaged the PTO at half throttle, the mower died. While this may have been half throttle position, it may have not been the RPM between idle and max. So now comes to the actual question, if the voltage regulator is bad, could it be the cause of my problem? I have verified with my voltage meter that I am receiving 30Vac from the alternator, which means that I have a 16 amp system. The down side, is that I do not have a meter than can test DC current over 10 amps, nor do I have the special tool (DC shunt) that will allow me to test with my meter. I just experienced an issue with my Cub Cadet where the voltage regulator was going bad causing the battery light to come on, but I never had it stall. it just seems too coincidental that the battery is not staying charged and this issue is happening on the same machine. I appreciate any help.

FYI, the engine is an 18HP Briggs Vanguard 356777 0115 E1

Mower is a LCT18BV483

Mike

 

[BlazNT]

You need a DC voltage tester to make sure but if memory serves me right you should have around 37v AC from the 2 same collored wires and 13.7v DC from red wire to ground.

 

[cruzenmike]

You need a DC voltage tester to make sure but if memory serves me right you should have around 37v AC from the 2 same collored wires and 13.7v DC from red wire to ground.

The 30 Vac is what I pulled from Briggs' Service Manual and I was spot on there with my multimeter. I haven't tested the DC voltage to the battery or at the terminals yet but the issue I found on my Cub Cadet was that I was reading the correct voltage at the red wire but there was no measurable current. Sounds impossible I know! The issue is that I cannot find a multimeter that will measure DC current over 10 amps. Based on my rectifier and ac voltage output I can see up to 16 amps through that red wire and I don't want to blow my new meter trying it out. Before pay $80 for a rectifier that I cannot return, I was hoping that someone could provide, with confidence, some insight into this problem.

 

[BigKingClipper]

Sounds like a minor issue to me. I had a similar issue on my exmark. They are very temperamental and seem to have a mind of their own at times. They are not good machines and I would get rid of it anyways, but if you are set on keeping it here is the fix... I took a 480uf capacitor and extended the end wires on the cap to reach across the battery terminals. Solder the two ends of the cap to the battery terminals. Strip the outer insulation and clamp from the end of your negative cable and solder this to your clamp on your positive cable. Make sure to electrical tape any exposed wire. Connect that positive puppy right up to the NEGATIVE battery terminal and completely bypass your low DC current issues. Very rarely will it even need a charge as long as the cap is doing its job. A Little mod that very few know.

 

[bertsmobile1]

The 30 Vac is what I pulled from Briggs' Service Manual and I was spot on there with my multimeter. I haven't tested the DC voltage to the battery or at the terminals yet but the issue I found on my Cub Cadet was that I was reading the correct voltage at the red wire but there was no measurable current. Sounds impossible I know! The issue is that I cannot find a multimeter that will measure DC current over 10 amps. Based on my rectifier and ac voltage output I can see up to 16 amps through that red wire and I don't want to blow my new meter trying it out. Before pay $80 for a rectifier that I cannot return, I was hoping that someone could provide, with confidence, some insight into this problem.

So the alternator is developing full power voltage that means the stator is OK and properly grounded
Now what is the DC rectified voltage ?
Very common for the ground strap to the rectifier to break so the mower never gets any of the power the alternator is generating as the DC side is open circuit.
While the initial power draw of an electric clutch is quite high, it is not as high as the cranking current that the battery supplies to the starter motor so the clutch creating a big enough power draw to cause a voltage drop sufficient to close the fuel solenoid is very small unless there is a dead short in the clutch or the clutch wiring.

OTOH an blown diode in the rectifier that is conducting both ways will cause a power draw while the engine is off as it will be trying to make the alternator motor.
Back in the early days the rectifier + feed wire was routed through the ignition switch to prevent this happening but this caused a lot of ignition switch and flat battery problems so every one other then JD , Walker & Grasshopper now run the feed directly to the battery thus bypassing the ignition switch.

The same diode problem will cause the battery to see pulsed DC not rectified DC similar to the old 3 & 5 single diode system used on smaller B & S engines.

The problem with your CUB is not incrediable but quite common and caused by the flat metal earth strap that grounds the rectifier fracturing so it s just touching most of the time thus you can get a voltage reading but very low current flow.
In bad cases you get enough arcing at the bad connection to see it glow a dull red at night.

Electrical problems need to be fixed not worked around.

 

[cruzenmike]

I believe I have the electrical issue all set. I am getting 14.2 volts at the battery terminal running min or max RPM. I did by the way replace the rectifier, clean off all electrical connections and apply dielectric grease before reconnecting everything.

In the end, this did not fix my original problem; I still have a bogging issue when engaging the PTO. It is possible that this is more of an engine/governor issue. I am going to start with some carb cleaner, a governor adjustment and checking the springs in the governor. If I am lucky, I will see a better response from the engine when engaging the PTO.

 

[bertsmobile1]

Forget the carb cleaner.
Pull the carb off & clean it with gas or an ultrasonic cleaner, fine brushes or a carb dip solution.
The spray can stuff can do more damage than good but is real handy for cleaning the outside of carbs.

Start the engine then work the governor by hand.
If the engine accelerates smoothly then your problem is in the governor or the amount of load being applied to the engine.

 

[BigKingClipper]

#cruzenmike, I noticed in all of your posts you keep mentioning the governor. The governor should not be tampered with at all, it is there for a reason and if you get to the point where you even consider playing with the governor as a fix, then something else is clearly not operating correctly within the machine. If you're electronics are operating correctly and your plugs are new and properly gapped, then yes the carburator may be playing a part in the revving. Float height? not allowing enough fuel to fill into the bowl. Jetting? clogged jets possibly. Intake Clean / Air Filter properly seated to form a seal? Exhaust bolts properly torqued? Simple checks should always be done first. Pulling the crankcase and messing with the governor should not even be considered as an option! I know you are new to the world of mowing and maintaining machines. I share with you my expert advice... start with the basics. If you aren't a professional, then don't experiment on your equipment. Simply maintain it and leave the wrenching to the professionals.

 

[cruzenmike]

#cruzenmike, I noticed in all of your posts you keep mentioning the governor. The governor should not be tampered with at all, it is there for a reason and if you get to the point where you even consider playing with the governor as a fix, then something else is clearly not operating correctly within the machine. If you're electronics are operating correctly and your plugs are new and properly gapped, then yes the carburator may be playing a part in the revving. Float height? not allowing enough fuel to fill into the bowl. Jetting? clogged jets possibly. Intake Clean / Air Filter properly seated to form a seal? Exhaust bolts properly torqued? Simple checks should always be done first. Pulling the crankcase and messing with the governor should not even be considered as an option! I know you are new to the world of mowing and maintaining machines. I share with you my expert advice... start with the basics. If you aren't a professional, then don't experiment on your equipment. Simply maintain it and leave the wrenching to the professionals.

I can appreciate what you are saying regarding not getting too deep into something in which I do not have experience. I have been wrenching on cars since I was a young boy and now in my 30's I do leave the repairs to the dealership, mostly because my cars are never more than 2 years old and also because time has become more precious now that I have kids. When it comes to the mower, I have 3 machines to cut with so I can afford the down time and don't mind tinkering with things. Thankfully, I have had some experience with the governor on my Cub Cadet; I actually removed the crank case and replaced the governor gear followed by a static governor adjustment. I surely do not want to get that deep into anything again, as that decision was driven by economics more than anything else; I just couldn't afford to pay someone for the repair but needed it fixed. This time around I stuck only to what I knew.

With that being said, here is what I did to resolve my issue:

Pulled air cleaner assembly and carb off. Cleaned outside of carb and around engine to make sure that no dirt or debris would get into the engine. I removed the governor assembly on the outside of the engine and replaced the springs. Put everything back together being sure that things were tight. I have a mini tac that I used to adjust the idle screw and bent the tangs to get the appropriate idle and max RPM as governed by the springs and linkages. I had already replaced my rectifier and cleaned all of my electrical connections, so I knew I was heading in the right direction when my mini tac showed that my.max rpm was set 300-400 too low. Once I had it set to the correct rpm per Briggs, I have had no issues with bogging when engaging the PTO and the battery is staying charged. Oh yeah, I also threw some sea foam into the tank to help clean out the fuel system. So far so good!!

Mike

 

[Telesis]

To BigKingCllipper... you mentioned something about the use of a 480uf cap across the battery terminals? I've read your post a dozen times and I can't quite understand it. I'd appreciate it if you'd take a moment and clarify how it's connected again, and what exactly you think it's doing...

Thanks