OP
rasorbackq
Platinum Member
If from a separate battery I hook up positive to plugs and neg to ground why wouldn't it glow?
How does a glow plug work?
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Everhard
Gold Member
I suggest confirming that power is going to the relay that feeds the glow plugs and that the relay is actually working. I had a similar situation (different brand tractor but the concept is the same.) where my glow plugs would work randomly. I at first thought it was my relay because when I swapped in a new one it worked but that didn't last for long and then it randomly stopped working again. Turned out to be the plug that relay plugs into, it wasn't making a good contact to one of the relay legs.
A bad contact anywhere in the circuit could cause the issue you're having.
E.
A bad contact anywhere in the circuit could cause the issue you're having.
E.
Vigo327
Platinum Member
Ok, so first off you should do the thing that narrows down the possibilities to the greatest extent possible, which is this:
If you consistently get the thing to 'manually' preheat by holding the key BETWEEN the on and start positions, then that guarantees a great many things:
So checking for consistently functioning manual preheat would rule out a whole bunch of possible issues right off the bat. None of the stuff on the above list could be broken or it wouldn't work, therefore it would mean all that stuff is good!
IF manual preheat consistently works but 'automatic' preheat doesn't, THEN:
Starts to control preheat, not necessarily starts TO preheat. The reason the glow controller has the coolant temp as an input is so it can tell whether the engine needs preheat.
If you look at the explanations in the PDFs, it works out this way:
IF the controller sees that the ignition is on by receiving power through Fuse 04 (5a) on the 0.5RB wire, AND the controller has a good ground from the 0.5B wire (which it should have all the time), THEN the controller will 'turn on'. Then it will decide WHETHER to power the glow plugs or not.
When the controller 'turns on', it will begin monitoring the resistance of the coolant temp sensor on the G10 circuit, which is the 0.5 LB wire. The sensor itself is a 1-wire connection, which means it grounds through its threads. If this sensor has ever been removed and then reinstalled with 'thread tape', that can cause the sensor to have an intermittent ground path and cause weirdness, so that's something to watch out for. The controller will watch the current flow through this wire (as a way of measuring resistance) to determine the coolant temp. The resistance specs of the sensor are given in the PDF:
Based on which way the resistance changes with temperature, you can determine what would happen from a bad connection or a short:
FYI, when you are looking at the wiring diagram the numbers next to the wires like 0.5 are in millimeters squared and it's the cross-sectional area of the wire, aka 'the wire size', and 0.5 is small. The RB and B are abbreviations for the wire colors (main color and stripe color) as shown in this part of the PDF:
If you consistently get the thing to 'manually' preheat by holding the key BETWEEN the on and start positions, then that guarantees a great many things:
- Your ignition switch receives battery power through the 3.0 W wire from the 'fuse(power)' fuse and puts it out on the C2 terminal (manual preheat signal) AND the BR1 terminal (general 'key on' power).
- Your glow controller receives the 'manual preheat signal' power AND the 'key on' power through the 5a fuse #04.
- Your glow controller has ground through the 0.5 B wire which is counter-intuitively labeled 'glow relay' instead of 'glow controller ground' which it actually is. This is probably because both the controller ground wire AND the relay coil's ground wire are spliced together where they join a larger ground wire, or both end at the same ring terminal.
- Your glow controller puts power out to coil of the glow relay on the 0.85 Y wire.
- The glow relay coil has ground from the 0.5 B wire.
- The glow relay coil is not open (broke).
- The glow relay gets power from the 'fuse(glow)' fuse.
- The glow relay's switch contacts are not so pitted/corroded as to cause intermittent lack of glow plug function (remember where i said consistently get it to manually preheat? Need to check 10-20 times to be thorough)
- The glow relay's switch has a good connection to the glow plugs through the 5.0 WR wire.
So checking for consistently functioning manual preheat would rule out a whole bunch of possible issues right off the bat. None of the stuff on the above list could be broken or it wouldn't work, therefore it would mean all that stuff is good!
IF manual preheat consistently works but 'automatic' preheat doesn't, THEN:
Starts to control preheat, not necessarily starts TO preheat. The reason the glow controller has the coolant temp as an input is so it can tell whether the engine needs preheat.
If you look at the explanations in the PDFs, it works out this way:
IF the controller sees that the ignition is on by receiving power through Fuse 04 (5a) on the 0.5RB wire, AND the controller has a good ground from the 0.5B wire (which it should have all the time), THEN the controller will 'turn on'. Then it will decide WHETHER to power the glow plugs or not.
When the controller 'turns on', it will begin monitoring the resistance of the coolant temp sensor on the G10 circuit, which is the 0.5 LB wire. The sensor itself is a 1-wire connection, which means it grounds through its threads. If this sensor has ever been removed and then reinstalled with 'thread tape', that can cause the sensor to have an intermittent ground path and cause weirdness, so that's something to watch out for. The controller will watch the current flow through this wire (as a way of measuring resistance) to determine the coolant temp. The resistance specs of the sensor are given in the PDF:
Based on which way the resistance changes with temperature, you can determine what would happen from a bad connection or a short:
- Since the resistance goes UP as it gets colder, a poor connection which added resistance would just make the engine appear colder to the module and the glow plugs may still work, maybe even stay on longer than necessary. However, the controller may be smart enough to know that if 19.5ohms is already -30c, then a number like 100ohms or 10,000ohms is just '********' in which case it may 'fault out' and refuse to do anything because it knows its 'eyes' are lying to it.
- Since the resistance goes DOWN as the engine gets warmer, a short to ground in the wire between the glow controller and the temp sensor would make the controller think the engine was already 'hot' and it wouldn't turn on the glow plugs at all. So, disconnect the wire from the sensor and check the resistance from the sensor's one male spade terminal to its metal (brass probably) housing and see if it roughly lines up with what it should be according to engine temp on the chart above. If it DOESN'T correlate, replace the sensor. If it DOES, then check the resistance between the wire you just unhooked from the sensor, and ground (sensor housing again should work, or any clean metal on the engine). That should read a very high ohm number (which will probably be abbreviated with K or M in front of the ohm symbol to indicate thousands or millions of ohms) or just say OL, aka too high to measure. However, if it gives you a low number in the range of say 20 ohms or less, that would shift the signal to show the engine being much warmer than it actually is (glow plugs may still work at some temps), and if it was a VERY low number like 5 ohms or less it would probably make the glow plugs never turn on at all.
FYI, when you are looking at the wiring diagram the numbers next to the wires like 0.5 are in millimeters squared and it's the cross-sectional area of the wire, aka 'the wire size', and 0.5 is small. The RB and B are abbreviations for the wire colors (main color and stripe color) as shown in this part of the PDF:
Last edited:
Vigo327
Platinum Member
For anyone else in the audience who may already be used to this kind of stuff (im an ASE Master auto tech) you may notice there are several INACCURACIES in the manuals where it describes the temperature sensors!
Ok so the PREHEAT temp sensor sends a signal to the INSTRUMENT CLUSTER? Hmm.
And the sensor for the METER (aka 'gauge') sends a signal to the PREHEAT controller? Sure, got it!
But look closely at the pic and you can see a clue that the technical writer didn't catch, but an actual mechanic might:
That right there is a yellow wire. Now look back at the wiring diagrams:
The yellow wire (with black stripe) goes to the gauge on the instrument cluster.
The temp sensor for the preheat controller would have a blue wire with black stripe. So the preheat sensor is definitely the one sticking straight up with a male spade terminal coming off it, NOT the one sticking out sideways with the stud in the center.
The table called 'sensor test' found on the preheat sensor page is also either nearly useless, or totally inaccurate for the actual preheat sensor:
First off this chart is garbage because where is 'connection 1' and 'connection 2' on a ONE WIRE sensor? And what is status "-"? There's no 'legend' or footnote helping you understand these. But let's double down and say there IS a wire going to terminal 2 of this 1-wire sensor that has 12v on it when the ignition switch is on. Well, if you didn't already notice that there weren't no two "connections" on your 1-wire sensor, or if you assume that the omitted information would tell you (if it existed) that connection 2 is actually the WIRE you just disconnected from the sensor, that 12v thing might seem plausible. But.. if you look at the resistance specs provided for the sensor, you can see it is designed to go down to 1.2ohms:
There's this little thing called Ohm's Law that says if you put 12v across a 1.2ohm resistance you will flow 10 amps. Which is interesting when you consider that the fuse that's giving the glow controller 12v in the first place, is a 5 amp fuse.
So is the circuit designed to pop the 5a fuse every time the tractor's engine coolant exceeds about 10c? Or is the circuit a 'pull down
' circuit that actually only has 12v when disconnected (which it doesn't tell you to do) and is current-limited so as not to blow the input fuse (it probably is) and when the wire is actually connected it will 'pull down' to a voltage that doesn't really matter because that's now how they expect you to test it (but they don't tell you how they DO expect you to test it)? Basically, is the manual just poorly written by someone who is not a mechanic, can't read a wiring schematic, doesn't know ohm's law, and neither do any of their proofreaders? Unfortunately that is very likely the case. The job title of 'technical writer' is basically shorthand for 'person serving as interpreter for someone talking about a subject the interpreter does not fully understand'. It's actually pretty normal. This is still way above the level of technical writing done by most of the people translating Chinese manuals to English!
Errors like that could send people on wild goose chases!
But, you have to be smart enough to go to the manual in the first place for this to become a problem for you, so for most people who can't fix this glow plug circuit.. this is not what's stopping them.
Ok so the PREHEAT temp sensor sends a signal to the INSTRUMENT CLUSTER? Hmm.
And the sensor for the METER (aka 'gauge') sends a signal to the PREHEAT controller? Sure, got it!
But look closely at the pic and you can see a clue that the technical writer didn't catch, but an actual mechanic might:
That right there is a yellow wire. Now look back at the wiring diagrams:
The yellow wire (with black stripe) goes to the gauge on the instrument cluster.
The temp sensor for the preheat controller would have a blue wire with black stripe. So the preheat sensor is definitely the one sticking straight up with a male spade terminal coming off it, NOT the one sticking out sideways with the stud in the center.
The table called 'sensor test' found on the preheat sensor page is also either nearly useless, or totally inaccurate for the actual preheat sensor:
First off this chart is garbage because where is 'connection 1' and 'connection 2' on a ONE WIRE sensor? And what is status "-"? There's no 'legend' or footnote helping you understand these. But let's double down and say there IS a wire going to terminal 2 of this 1-wire sensor that has 12v on it when the ignition switch is on. Well, if you didn't already notice that there weren't no two "connections" on your 1-wire sensor, or if you assume that the omitted information would tell you (if it existed) that connection 2 is actually the WIRE you just disconnected from the sensor, that 12v thing might seem plausible. But.. if you look at the resistance specs provided for the sensor, you can see it is designed to go down to 1.2ohms:
There's this little thing called Ohm's Law that says if you put 12v across a 1.2ohm resistance you will flow 10 amps. Which is interesting when you consider that the fuse that's giving the glow controller 12v in the first place, is a 5 amp fuse.
So is the circuit designed to pop the 5a fuse every time the tractor's engine coolant exceeds about 10c? Or is the circuit a 'pull down
' circuit that actually only has 12v when disconnected (which it doesn't tell you to do) and is current-limited so as not to blow the input fuse (it probably is) and when the wire is actually connected it will 'pull down' to a voltage that doesn't really matter because that's now how they expect you to test it (but they don't tell you how they DO expect you to test it)? Basically, is the manual just poorly written by someone who is not a mechanic, can't read a wiring schematic, doesn't know ohm's law, and neither do any of their proofreaders? Unfortunately that is very likely the case. The job title of 'technical writer' is basically shorthand for 'person serving as interpreter for someone talking about a subject the interpreter does not fully understand'. It's actually pretty normal. This is still way above the level of technical writing done by most of the people translating Chinese manuals to English!
Errors like that could send people on wild goose chases!
But, you have to be smart enough to go to the manual in the first place for this to become a problem for you, so for most people who can't fix this glow plug circuit.. this is not what's stopping them.
Last edited:
OP
rasorbackq
Platinum Member
Lots of info to look at after the arctic blast is done. -17C -25 windchill. Tractor plug plugs worked and fired right up.
Tomorrow -28C and -39 windchill.
Thanks guys.
Tomorrow -28C and -39 windchill.
Thanks guys.
number two
Veteran Member
- Joined
- Apr 2, 2007
- Messages
- 1,399
- Location
- Northern Lower Michigan
- Tractor
- Kubota B3030HSDC Kubota L2501HST
Awesome posts!For anyone else in the audience who may already be used to this kind of stuff (im an ASE Master auto tech) you may notice there are several INACCURACIES in the manuals where it describes the temperature sensors!
View attachment 782181
Ok so the PREHEAT temp sensor sends a signal to the INSTRUMENT CLUSTER? Hmm.
View attachment 782182
And the sensor for the METER (aka 'gauge') sends a signal to the PREHEAT controller? Sure, got it!
But look closely at the pic and you can see a clue that the technical writer didn't catch, but an actual mechanic might:
View attachment 782183
That right there is a yellow wire. Now look back at the wiring diagrams:
View attachment 782184
The yellow wire (with black stripe) goes to the gauge on the instrument cluster.
View attachment 782186
The temp sensor for the preheat controller would have a blue wire with black stripe. So the preheat sensor is definitely the one sticking straight up with a male spade terminal coming off it, NOT the one sticking out sideways with the stud in the center.
The table called 'sensor test' found on the preheat sensor page is also either nearly useless, or totally inaccurate for the actual preheat sensor:
View attachment 782187
First off this chart is garbage because where is 'connection 1' and 'connection 2' on a ONE WIRE sensor? And what is status "-"? There's no 'legend' or footnote helping you understand these. But let's double down and say there IS a wire going to terminal 2 of this 1-wire sensor that has 12v on it when the ignition switch is on. Well, if you didn't already notice that there weren't no two "connections" on your 1-wire sensor, or if you assume that the omitted information would tell you (if it existed) that connection 2 is actually the WIRE you just disconnected from the sensor, that 12v thing might seem plausible. But.. if you look at the resistance specs provided for the sensor, you can see it is designed to go down to 1.2ohms:
View attachment 782179
There's this little thing called Ohm's Law that says if you put 12v across a 1.2ohm resistance you will flow 10 amps. Which is interesting when you consider that the fuse that's giving the glow controller 12v in the first place, is a 5 amp fuse.
View attachment 782180
So is the circuit designed to pop the 5a fuse every time the tractor's engine coolant exceeds about 10c? Or is the circuit a 'pull down
' circuit that actually only has 12v when disconnected (which it doesn't tell you to do) and is current-limited so as not to blow the input fuse (it probably is) and when the wire is actually connected it will 'pull down' to a voltage that doesn't really matter because that's now how they expect you to test it (but they don't tell you how they DO expect you to test it)? Basically, is the manual just poorly written by someone who is not a mechanic, can't read a wiring schematic, doesn't know ohm's law, and neither do any of their proofreaders? Unfortunately that is very likely the case. The job title of 'technical writer' is basically shorthand for 'person serving as interpreter for someone talking about a subject the interpreter does not fully understand'. It's actually pretty normal. This is still way above the level of technical writing done by most of the people translating Chinese manuals to English!
Errors like that could send people on wild goose chases!
But, you have to be smart enough to go to the manual in the first place for this to become a problem for you, so for most people who can't fix this glow plug circuit.. this is not what's stopping them.
Thanks for taking the time and sharing!
OP
rasorbackq
Platinum Member
-30C -41 windchill.
Glow plugs are working but too cold for battery. Turned over slowly but not going to start today.
. Calling for +5 tomorrow.
Glow plugs are working but too cold for battery. Turned over slowly but not going to start today.
. Calling for +5 tomorrow.
OP
rasorbackq
Platinum Member
Morning.. Are these pics from a Branson 4720H? or just a outline how things work? Some of it looks right compared to the side of my engine But the large box above the alternator I don't think I have. Just going from memory.For anyone else in the audience who may already be used to this kind of stuff (im an ASE Master auto tech) you may notice there are several INACCURACIES in the manuals where it describes the temperature sensors!
View attachment 782181
Ok so the PREHEAT temp sensor sends a signal to the INSTRUMENT CLUSTER? Hmm.
View attachment 782182
And the sensor for the METER (aka 'gauge') sends a signal to the PREHEAT controller? Sure, got it!
But look closely at the pic and you can see a clue that the technical writer didn't catch, but an actual mechanic might:
View attachment 782183
That right there is a yellow wire. Now look back at the wiring diagrams:
View attachment 782184
The yellow wire (with black stripe) goes to the gauge on the instrument cluster.
View attachment 782186
The temp sensor for the preheat controller would have a blue wire with black stripe. So the preheat sensor is definitely the one sticking straight up with a male spade terminal coming off it, NOT the one sticking out sideways with the stud in the center.
The table called 'sensor test' found on the preheat sensor page is also either nearly useless, or totally inaccurate for the actual preheat sensor:
View attachment 782187
First off this chart is garbage because where is 'connection 1' and 'connection 2' on a ONE WIRE sensor? And what is status "-"? There's no 'legend' or footnote helping you understand these. But let's double down and say there IS a wire going to terminal 2 of this 1-wire sensor that has 12v on it when the ignition switch is on. Well, if you didn't already notice that there weren't no two "connections" on your 1-wire sensor, or if you assume that the omitted information would tell you (if it existed) that connection 2 is actually the WIRE you just disconnected from the sensor, that 12v thing might seem plausible. But.. if you look at the resistance specs provided for the sensor, you can see it is designed to go down to 1.2ohms:
View attachment 782179
There's this little thing called Ohm's Law that says if you put 12v across a 1.2ohm resistance you will flow 10 amps. Which is interesting when you consider that the fuse that's giving the glow controller 12v in the first place, is a 5 amp fuse.
View attachment 782180
So is the circuit designed to pop the 5a fuse every time the tractor's engine coolant exceeds about 10c? Or is the circuit a 'pull down
' circuit that actually only has 12v when disconnected (which it doesn't tell you to do) and is current-limited so as not to blow the input fuse (it probably is) and when the wire is actually connected it will 'pull down' to a voltage that doesn't really matter because that's now how they expect you to test it (but they don't tell you how they DO expect you to test it)? Basically, is the manual just poorly written by someone who is not a mechanic, can't read a wiring schematic, doesn't know ohm's law, and neither do any of their proofreaders? Unfortunately that is very likely the case. The job title of 'technical writer' is basically shorthand for 'person serving as interpreter for someone talking about a subject the interpreter does not fully understand'. It's actually pretty normal. This is still way above the level of technical writing done by most of the people translating Chinese manuals to English!
Errors like that could send people on wild goose chases!
But, you have to be smart enough to go to the manual in the first place for this to become a problem for you, so for most people who can't fix this glow plug circuit.. this is not what's stopping them.
Maybe this info will assist.
when the engine is warm the glow plugs are not required or don't lite up at start. I was confused a bit with Manual and automatic glow plug starting. but I think its as clear as mud.
Also I don't know where the glow controller and the relays are located.
I know where the starter hydraulic pump and alternator are on the left side.
Right side glow plugs. fuel pump . I wish I was a diesel mech with some knowledge
5030
Rest in Peace
- Joined
- Feb 21, 2003
- Messages
- 28,967
- Location
- SE Michigan in the middle of nowhere
- Tractor
- Kubota M9000 HDCC3 M9000 HDC
Gee, glo plugs work by glowing.... DUH
Vigo327
Platinum Member
Everything i posted about is in the PDF manuals that LouNY posted back on page 2 of this thread, post #13.
MaxLee
Silver Member
I had a wire broke coming out of the glow plug heater control. Mine wouldn't light on dash at all ( could crack it over for ever)unless I turned key all the way just before the start position. It would come on and a would count o 15 then turn to start it. I thought it was module and when I decide to see what part I need I found the wire.
MaxLee
Silver Member
find the module then do ohms test and see if any wire broke, check voltage in and out. it seem more involved then it is. basic relay low voltage stuff , make sure key is on when checking voltage , actually I would start at the glow plugs see if voltage there then work back, could even be the key switch , sorry about confusion, thinking while I am typing LOL
