# kohler 4.5ckm21-rv generator puts out 50% power



## mhooker32 (Nov 9, 2020)

myself and my friend both have kohler 4.5ckm21-rv generators. 2 cyl rv units from the 80's. mine runs like a top and powers very well. his runs like a top, but only puts out 50% power. about 50 volts on the 110c circuit and 110v on the 220 side. both hots to neutra' on the 200 is 50 or so volts, hot to hot is about 110. the hertz are good at 60.5 no matter where you test. brining up the rpm will get the 50 up to around 63, but the hertz go to the high seventies. any7 idea what could be wrong or how to troubleshoot this? thanks


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## iowagold (Jan 22, 2020)

a few questions first.
how good are you with electrical and electronics?
and do you have a good fluke multi meter?
do you have the service manual?

if you are a seasoned tech:
set the hz to 60 hz period.
the voltage and current are set in the excitation.

you will need to check a few things with the gen off and wires disconnected.
rotor, and stator resistance.

all connections for water damage.
check the pcb for water and heat damage.

snap a few pix for us as well


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## iowagold (Jan 22, 2020)

you might head over to smoke stack on this old dog
Kohler 4.5cm21 generator help needed


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## mhooker32 (Nov 9, 2020)

iowagold said:


> a few questions first.
> how good are you with electrical and electronics?
> and do you have a good fluke multi meter?
> do you have the service manual?
> ...


i can handle a fluke very well, can read schematics, and somewhere i have the manual,but have to find it. i also have a working unit, but because its working, i'm hesitant to open it up . i will find the manual, and take some pics. my friend , the owner, also has the manual if i need it. it would be a shame to not get it working, it runs very well. i should note, it doesnt stay running when you release the start button. my understanding is thats correct , if the voltage output isnt correct it will shut down the engine. . it also doesnt output a charging voltage to the battery, runs at 11.9v battery. i checked both fuses that hook into the control panel( good) and also that diode with the spade connectors on each end. diode is good. also, no hung or low brushes. pics and more tomorrow. thanks


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## iowagold (Jan 22, 2020)

look for bad connections.
that is a common issue on the rv units.

make sure the battery is full charged be fore you start on the project..
it should be at 12.8 vdc just sitting there with no load.

battery charging should be at 13.8 to 14.2 vdc.


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## mhooker32 (Nov 9, 2020)

iowagold said:


> look for bad connections.
> that is a common issue on the rv units.
> 
> make sure the battery is full charged be fore you start on the project..
> ...


 opened it up didnt see any bad connections. there is one wire labeled "B" that isnt connected to anything, its taped on the end. there is also a B1 and B2 that are connected correclty. i opened up my unit. looking for the B wire. didnt see it, but didnt go digging to deep, i dont need a second unit running poorly  . here is a pic of the unit with the 505 power output. i should have the manual later today, my friend is dropping it off.


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## mhooker32 (Nov 9, 2020)

mhooker32 said:


> opened it up didnt see any bad connections. there is one wire labeled "B" that isnt connected to anything, its taped on the end. there is also a B1 and B2 that are connected correclty. i opened up my unit. looking for the B wire. didnt see it, but didnt go digging to deep, i dont need a second unit running poorly  . here is a pic of the unit with the 505 power output. i should have the manual later today, my friend is dropping it off.


should read 50% power output, not 505. didnt see anyway to edit that.


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## mhooker32 (Nov 9, 2020)

i found a pic of the regulator online. one of the 5 terminals is a "B" . im thinking its the B that is taped off and not connected to anything? cant even see the regulator, i guees to have to remoeve the end of the generator assembly? thanks


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## mhooker32 (Nov 9, 2020)

well, i though i had it, but no. that unconnected B wire ran behind the panel, i assume going to the b terminal on the regulator. i connected a wire to it. when its unconnected, the voltage AC output is 50v on the 110 side, about 110 across L1 and L2. i thought if i applied battery voltage to the B wire in question, it would allow the regulator to work. however, when it connected to 12 positive, the Ac output drops to near zero. now im stuck.


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## mhooker32 (Nov 9, 2020)

its the regulator. . it has 6 wires, not 5 and doesnt look like anything in the manuals i have. i pulled the regulator out of mine and tried the now known bad one. did the exact same thing, 50% voltage output. anyone know where to get one? see pic. or does anyone have a schematic of the regulator , i could possibly build one.


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## iowagold (Jan 22, 2020)

those clear ice cube relays are a bad design for out door...
they are not hermetically sealed.
or lay mans terms they are not water proof...
moisture gets in them and the contacts get damp over time....
we replace them by the bucket loads in some equipment...

if you are handy with component repair.
remove the relays and take them apart, use non printed paper strips to clean the contacts.
yea a total pain..
but it works!
*warning do not use any chems to clean the contacts!*
the plastic used in these ice cube style relays will melt with any chems.

after the clean job put them back together and see what you have.

also check the brushes and slip rings.
blow out the carbon, and use 400 grit to clean the slip rings
watch the slots if they have them they may need attention if they are plugged up.


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## mhooker32 (Nov 9, 2020)

i sent the regulator to flight systems for repair. even though its potted, he said he has done them before. should be good to go when i get it back. i'll post the result.


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## mhooker32 (Nov 9, 2020)

mhooker32 said:


> i sent the regulator to flight systems for repair. even though its potted, he said he has done them before. should be good to go when i get it back. i'll post the result.


a guy online had a unit not running. i gave him a hundred bucks for anything he could pull out of it, carb, pump, controls, and the regulator. it came a few days ago and the regulator is good, steady 240v now. i also had mine repaired by flight systems, it came today, so i have a spare if needed. the turn around was fast, and the cost was 65.00 with the shipping. cant beat that, i was pleasantly surprised.


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## iowagold (Jan 22, 2020)

spare parts are always a great plan!


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