Need help choosing a new capacitor

Thread Starter

Tscjcampbell

Joined Jul 27, 2018
3
I have a Onan generator control board that i want to replace the capacitor in but i cant seem to find a direct replacement for it. It is a mkt 1822 din 44122 w6.
Any help would be appreciated,
Onan control board (2)_LI.jpg
Thanks, Tim
 

ebp

Joined Feb 8, 2018
2,332
0.1 K 400
means 0.1 µF (microfarads), ±10% tolerance, 400 volts DC maximum

MKT means it is metalized polyester film
The DIN number just refers to some standard to which it complies.

In order to find a replacement, you will need to know the dimensions and the lead spacing. Overall dimensions don't matter too much as long as the new part will fit. Lead spacing is important because the leads on the "box" type like that are short and stiff. The spacing will be metric.

Any metalized polyester film cap of the appropriate value and voltage rating and size will do. 10% tolerance is common so it shouldn't be a problem. 5% tolerance would be OK.
 

Thread Starter

Tscjcampbell

Joined Jul 27, 2018
3
EBP, Thank you.

Sorry for what probably seems like simple questions, But I have never worked on a board before. And rather than sink $150 into a new control board i'd thought I might try to fix this one rather than buy new.
With that being said, do you have any idea what the blue square thing in the bottom left is? I put it in my component tester and it said it was a resistor with like a .4 ohm resistance. I tried to google MCI 2.0 and MCL 2.0 and didn't see anything useful.
 

ebp

Joined Feb 8, 2018
2,332
I think it is probably a 2 ampere self-resetting "fuse" - basically a special sort of resistor whose resistance is low when cold but if it self-heats sufficiently with overcurrent the resistance goes up dramatically. This doesn't turn current off, but keeps it low enough to prevent other things from burning up. They are sometimes called PTC (postive temperature coefficient) circuit interrupters or PTC overcurrent protectors or the like. Polyswitch, now a division of Littelfuse, is a fairly well known brand in North America.

MCI is probably the manufacturer. I've seen it before but can't remember what the letters stood for. I don't think it still exists. It may have been a house brand for one of the big components distributors. Given the measured resistance, I suspect it is OK.

If the board is quite old, the first thing I would replace would be the electrolytic capacitors C2 and the one sort of nestled among the relays. They do degrade with age and are inexpensive and easy to replace. The other parts on the board tend to be highly reliable. Relay contacts do fail eventually. The (rocker?) switch is something I would check. Carefully inspect all the solder joints, especially on the bigger pins such as the connectors.

Were CR2 and CR4 never there, or did you remove them?
 
Last edited:

Thread Starter

Tscjcampbell

Joined Jul 27, 2018
3
Ebp,
Thank you for the information on the fuse.
I plan on replacing the electolytic capacitors. They didn't look bad or leaking, but I know they have a lifespan. I believe the board to be around 20 years old. I'v tested the relays as far as the coils having the right ohm reading, and the relays activating with 12v provided to the pins. The on/off rocker switch while it looks crusty, test and works properly. Cr2 and cr4 were there, but I had removed them prior to the picture. So far of the diodes and capacitors I've removed they have all checked out, but I still have a few to go.
Thanks again for your help,
Tim
 
Top