Difficulty starting DK45SE in cooler weather (40's F)

[k0ua]

Well it is too late now, but I would have ohmed the glow plugs with the rail off. They should be a little under 1 ohm , but not shorted. a little less than 1 ohm at 12.6 volt would draw a little over 12 amps so about 150 watts per plug. Now you say with the bar off you measure 12.6 volts on the bar, but with it connected you measure near 0 volts. So if none of the glow plugs are a dead short, and if they were, there should be a fuse blowing somewhere. So the only other explanation for the 0 volts on the rail when connected is there is a high resistance connection somewhere in the supply path to the plugs. Perhaps the relay contacts are burnt, or a high resistance connection to them. There is no question in my mind that this is your problem, you just have to find the high resistance that is causing the very low current flow and the extreme drop in voltage. When they get the piece of the glow plug out and the head back on and a new plug put in then they can start to troublshoot the problem again..because it will still be there. Your measurement of 0 volts on the rail when on and 12.6 volts when it is disconnected from the plugs tell the tale. E=IR Ohms law, is not just a good idea it is the law Think of your problem using this simple example.. Take a 12 volt battery and a taillight and hook them together. The tail light lights to full brilliance. Lets say for ease of calculation that the lamp pulls 1 amp of current and since P=EI the E(electromotive force, commonly called Volts) is 12 and we said the I (current measured in Amperes or amps) is 1 amp the wattage for the lamp is 12 Watts and the resistance of the bulb is about 12 ohms. Now put a 10000 ohm resistor in series with the 12 ohm lamp. Will the lamp light to full brilliance? No it will not, the resistor will limit the current to about .001 amps and the voltage will drop on the terminals of the lamp to near 0 . But if you remove the load (the lamp) and measure the battery voltage thru the 10,000 ohm resistor you will measure 12 volts. It is only when you put a load on this voltage path that the voltage will drop and the current will be very low and the power dissipated in the load will be very low. If you will take your meter and measure backward from the glowplug rail with 0 volts until you encounter 12 volts again you can isolate the component or wiring or connection that has the high resistance and is causing the voltage drop and current limiting.

James K0UA

 

[murphy1244]

Well it is too late now, but I would have ohmed the glow plugs with the rail off. They should be a little under 1 ohm , but not shorted. a little less than 1 ohm at 12.6 volt would draw a little over 12 amps so about 150 watts per plug. Now you say with the bar off you measure 12.6 volts on the bar, but with it connected you measure near 0 volts. So if none of the glow plugs are a dead short, and if they were, there should be a fuse blowing somewhere. So the only other explanation for the 0 volts on the rail when connected is there is a high resistance connection somewhere in the supply path to the plugs. Perhaps the relay contacts are burnt, or a high resistance connection to them. There is no question in my mind that this is your problem, you just have to find the high resistance that is causing the very low current flow and the extreme drop in voltage. When they get the piece of the glow plug out and the head back on and a new plug put in then they can start to troublshoot the problem again..because it will still be there. Your measurement of 0 volts on the rail when on and 12.6 volts when it is disconnected from the plugs tell the tale. E=IR Ohms law, is not just a good idea it is the law Think of your problem using this simple example.. Take a 12 volt battery and a taillight and hook them together. The tail light lights to full brilliance. Lets say for ease of calculation that the lamp pulls 1 amp of current and since P=EI the E(electromotive force, commonly called Volts) is 12 and we said the I (current measured in Amperes or amps) is 1 amp the wattage for the lamp is 12 Watts and the resistance of the bulb is about 12 ohms. Now put a 10000 ohm resistor in series with the 12 ohm lamp. Will the lamp light to full brilliance? No it will not, the resistor will limit the current to about .001 amps and the voltage will drop on the terminals of the lamp to near 0 . But if you remove the load (the lamp) and measure the battery voltage thru the 10,000 ohm resistor you will measure 12 volts. It is only when you put a load on this voltage path that the voltage will drop and the current will be very low and the power dissipated in the load will be very low. If you will take your meter and measure backward from the glowplug rail with 0 volts until you encounter 12 volts again you can isolate the component or wiring or connection that has the high resistance and is causing the voltage drop and current limiting.

James K0UA

Good job James.. Well thought out and explained.

 

[k0ua]

Thanks Murph, I did look in the workshop manual, and if there is 12 volts on the rail, then the relay has to be pulled up by its 86 ohm coil. But the contacts could be burnt and be a high resistance. It looks like the next component in line after the relay contacts is the 60 amp slow blow fuse. According to the manual the wire is 5mm Orange to and from the relay contacts.

James K0UA

 

[schweizer]

Thanks guys. I understand what you are saying James, and I understand Ohms law. If the relay contacts are burnt, you would think replacing the preheat controller or timer relay would solve the problem. I must not have found the real relay yet. Since everyone likes diagrams...

 

[k0ua]

Ok I think you said you replaced the display unit which one of its functions is to take inputs from the temp sensor and decide how long to operate the glow relay for preheat and whether to operate the glow relay for post start. And the Actual Glow relay which switches high current to the glow plug rail. and is the 2nd relay from the left on the firewall. and is fed with 5mm Orange wires. If there is 12 volts on the glow plug rail when it is disconnected the contacts of this relay must be operated, If you pull the connections on this relay you should hear it fall and pickup when the key is in the preheat position and the temp is cold enough to allow the controller to energize the glow relay coil. Its coil is controlled by output of pin 7 of the display unit, it is a brown wire. If the glow relay has been replaced to eliminate the possibility of burned high current contacts, then perhaps a bad crimp or connection in the plug to the relay or further back to the 60 amp slow blow fuse.. My point is if the glow relay coil is operated, and by your measurements I have every reason to believe it is, then if you have 0 volts on the glow plug rail when it is connected, and if one or more of the glow plugs are not dead shorted to the engine block, and if they were it should have blown the 60 amp fuse or at the very least burned up (carboned up) the glow relay contacts so that they become a high resistance and limit the current so that the fuse will not blow. My point is if there is 12 volts on the rail , then it comes (according to the schematic) from the glow relay high current contacts and the other side of the relay goes to the 60 amp slow blow fuse, and the other side of the fuse goes to the battery. There has to be a high resistance joint in there somewhere or you would have high current to deliver to your load of the glow plugs. I guess this is all academic now as your tractor is in the hands of the dealer, and I am sure he will fix it.

James K0UA

The display unit is installed in the middle of the
shield plate in the engine compartment.
Function
1. Counting function for hour meter on instrument cluster
When the charge voltage is supplied from the alternator
after starting the engine, it controls the hour
meter on the instrument cluster.
2. Preheat adjustment function (automatic)
It detects the coolant temperature. If the temperature
is below 0°C (32 °F), it controls the operating
time of the glow plug.
Specification
1. Rated voltage: DC 12 V
2. Usage temperature: -20 °C ~ +80 °C
Preheat operation specifications
•
•
•
FFuunncctitoionn
Item Operating condition
Operating time
Preheat lamp
ON time
Temperature sensor
≥ 1.6 ㏀
8 seconds
Temperature sensor
< 1.6 ㏀
0 second
Post-heating
time
Temperature sensor
≥ 1.6 ㏀
15 ± 3 seconds
• Temperature sensor resistance (reference)
Temperature(˚C) Resistance(㏀)
-40 48.14
-20 15.48 ± 1.35
0 5.790
20 2.45 ± 0.14
30 1.6 ± 0.15
60 0.5865
80 0.3222
100 0.1884
110 0.1471 ± 0.002

 

[schweizer]

Yes, it's academic now, but the dealer is going to charge me fortune to fix it. Wish I had asked you guys sooner. I really didn't want to take apart the whole wiring harness to trace out which wire was going where, but that's what I needed to do. Thanks for the help!

Marcus

 

[ritcheyvs]

I'd add one detail to James' explanation. Things like glow plugs and light bulbs change their resistance a lot as they heat up. In other words, their resistance will be quite low when cold (room temp) but the resistance increases a lot as they get hot. So ohming out the glow plugs is a great idea but expect low resistance values when cold. For example, if the nominal glow plug current is 12 amps you'd expect the resistance to be one ohm ... at operating temp. But a good might read 1/3 to 1/2 ohm when cold. This is one reason it's good to be able to measure the current through the plug.

 

[k0ua]

I'd add one detail to James' explanation. Things like glow plugs and light bulbs change their resistance a lot as they heat up. In other words, their resistance will be quite low when cold (room temp) but the resistance increases a lot as they get hot. So ohming out the glow plugs is a great idea but expect low resistance values when cold. For example, if the nominal glow plug current is 12 amps you'd expect the resistance to be one ohm ... at operating temp. But a good might read 1/3 to 1/2 ohm when cold. This is one reason it's good to be able to measure the current through the plug.

Agreed, good point. I have a simple current meter for High DC currents that you just place up against a wire and it measures the current thru induction. Probably not extremely accurate but will give you an idea if high currents are flowing or not. It has two scales 0 to 75 and 0 to 300 amps.

James K0UA

 

[schweizer]

Update: Tractor is coming home on Tues next week -- cost $800+ to get it fixed. Maybe I didn't work it hard enough and the glow plugs did get all carboned up. It's been to the dealer twice in the past 6 mos for electrical problems. The last $800 repair was for a shorted wiring harness under one of the rear fenders. At that time they found loose frame bolts and FEL bolts and tightened them. This time, with the broken glow plugs, they found loose FEL and frame bolts again. Locktite'd again. Should I be going around checking every bolt periodically? The friend who is bringing home my tractor bought the same DK45HST as I have. (In fact, that's how we met -- at the dealer's when he was picking it up.) He's a little frustrated because he feels the grill guard was weak (smashed within hours), and the step ladder welds broke. Then again, I don't know how he treats his tractor... Until now I had really liked my tractor.

Marcus

 

[kco]

You should regularly check for loose hardware. The loader manual says to torque the loader bolts every 25 hours. I found one or two of mine slightly loose every time I checked them. Then my dealer said to reinstall them with blue loctite, and they have not moved since. He told me that in the summer of 2011. I purchased the tractor (DK35) in April of 2011. So I think Kioti must have decided loctite is necessary some time after then.

The manual also says to torgue the wheel bolts regularly. The first time I did that (at 50 hrs) there were slightly loose bolts on all wheels, but more on the fronts. The next checks found one or two front wheel bolts moved very slightly. Now there is no movement (I'm at 440 hrs) in any loader bolts or wheel bolts. Loctite fixed the loader bolts and perhaps the wheel bolts just had to "settle in".

I recently found I lost one of the small bolts holding the pin at a loader pivot point. I also lost a sway bar pin because the hairpin was knocked out while brush hogging. I have since replaced those keeper pins with bolts with lock nuts.