Low voltage at glow coil

   / Low voltage at glow coil #1  

larryhughes

New member
Joined
Oct 12, 2012
Messages
2
Location
quitman, texas
Tractor
stt52 scag,. John Deere 830 and Kubota ZD21F
Just purchased a Kubota ZD21F, my first diesel and first Kubota. Starts but iffy it seems. Checked voltage to each coil and have just over 6 volts. Removed each coil and ohmed with continuity. Did not notice the actual ohm reading. Also, the light that indicates the coil is on does not light. Hard to get to the bulb but managed and it looks good, element seems to be ok, but very difficult to get to without removing fender, which looks tough.

The engine does start always after the second, sometimes 3rd time, trying about 10 seconds each time. Is that what I should expect? Still don't understand the 6 volt reading. Any ideas.
 
   / Low voltage at glow coil #2  
Measure:

Voltage at the battery

Voltage at the input of the heater relay
Voltage at the output of the heater relay
Voltage at the heater connection disconnected from the heater.
Voltage at the heater connection when connected to the heater.

USE THE SAME GROUND for all measurements

Heaters (glow plugs) are big current draw items. They could easily show 6V at the terminal when pulling max current if the battery and connections were anything but brilliant.
 
   / Low voltage at glow coil #3  
If you checked the glow plugs with an ohm meter but didn't get a reading they could be open. In other words bad. Each plug should be checked by itself and should show a resistance reading. I had a similar problem on my previous tractor (twice). Once I had one plug show a resistance reading, the second showed no reading meaning an open circuit, and the third plug read it was shorted. With this situation only one glow plug was working out of three.

Disconnect the wire that feeds your plugs and connect to a volt meter then turn on the key so the glow plug timer activates and read the voltage. On mine it read 12V while disconnected. Also see if the light comes on with the wire disconnected.

I suspect you have a bad glow plug timer controller or one or more bad plugs. By cycling the switch 2 or 3 times you are getting the working plug to heat up enough to get it to fire up.

Even if the controller and plugs are not working, just by you cranking it over 2 or 3 times you are building heat in the cylinders allowing it to eventually fire up.
 
   / Low voltage at glow coil
  • Thread Starter
#4  
Sounds like you may have the right idea, a bad or weak controller. Can you tell me where such an apparatus is located? It looks like the fender must be removed to get to just about everything and I have no idea where to start. I did remove the bulb holder from the socket but did not pull the bulb as I could just barely get my fingers on the bulb. This is the bulb in the indicator, which does not light. Thanks for your reply.
 
   / Low voltage at glow coil #5  
I have no idea where yours would be located. Not familiar with your tractor. On the Mahindra that I changed the timer was located under the dash panel on the left side easily accessed by removing a couple bolts.
 
 
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