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Discussion Starter #1
My glow plug light won't turn off! It used to work fine. I can start the tractor, and it runs (with light still on). I'm assuming it isn't great to run it this way. Is there a timing circuit that controls how long it stays on or is it based on something else?
 

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Can't remember, but thought that meant something else, like water in the fuel or something. Pehaps someone with an Owner's Manual could look it up.

Otherwise, I'd hope the glow plugs are not being energized all the time. That will burn them and the circuit out. You could check that part pretty easily with a volt meter or test light to the glow plugs themselves.
 

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Don't see anything about water. 332 doesn't have a water seperator anyway, only the 430. Think you need to replace the module according to the manual. See attached snapshot.
 

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Discussion Starter #5
I suspected it was probably something like this but wanted to get some opinions. Sometimes tribal knowledge can reveal more than a manual! I didn't get a chance to put a test lamp on when I noticed it, I will do that tommorow and then look in the manual.
 

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I'd disconnect the glow plugs and check the output voltage with a volt meter. Looks like the lamp and the plugs run off 2 different transistors, so its quite possible that the light is just staying on but the plugs are actually turning off.

If it is the module, and you're interested in saving some money, I can probably find some replacement parts (I'm an electrical engineer) for the internals of that glow plug module (those transistors and, I'm assuming, comparators, and capacitors). All the parts are probably marked with a part number. If you can get to the glow plug module, snap some pictures and get some part numbers off the ICs. There is probably $10 worth of parts in there, and deere wants $55.
 

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To be honest, you could remove the controller all together if need be. Just install a high amperage relay and a momentary switch in it's place. Just push it for a few seconds before starting on a cold day.

All the controller does it make it an automatic thing depending on temperature. A deluxe feature. On older JD compacts you turned the keyswitch backwards to preheat manually. No controller, and you controlled the heating time as you saw fit.
 

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Discussion Starter #8 (Edited)
Ok I've checked out the module. With the key on the heater position, the solenoid in the picture turns on and activates the glow plug. However, it never turns off, so it definitely is a problem in this unit somewhere. It would be easy enough to replace a component if I knew which one to replace! There are two individual transistors, and an IC chip. The IC is labled "LM2903N K8711". The "glow plug lamp transistor is marked "C517 PH60", and the relay transistor is"S (weird kind of s) V3 C639". There is mention of a thermistor in the diagram but I'm not sure where it is yet.












I'm not sure where to go at this point. I have some general electrical skills (I'm a mech engineer) but should I just go replacing everything? The IC at least seems available at first glance.
 

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Discussion Starter #9
The thermistor is in the 2nd to last photo, top left. from the top down it is gold, red, purple, orange, white or yellow.
 

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check the resistance across the 2 capacitors, and the from collector to emitter on the transistors. If any appear as a short, then that's probably the issue. Look and see if anything seems burnt.

See here for a schematic of which is the collector and which is the emitter.
http://upload.wikimedia.org/wikipedia/commons/a/aa/BJT_symbol_NPN.svg

If all those look good, you might try putting 12V on it and seeing if the comparator is outputting the correct voltage and the thermistor is changing resistance as it heats up (as current flows through it).
 

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actually, the big blue cap on the right in the very last picture looks like the top has popped out a little bit. The top doesn't have a ridge like the one on the left. It kinda looks pushed up (third picture shows it best). Double check me and make sure its not the camera angle. That is a sure tell sign of an exploded electrolytic capacitor, which should appear as a short.

One of those caps is setting your time constant. If it were short, then it would probably stay on forever, which is what your experiencing.
 

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Discussion Starter #12
The cap in question seems to start at around 410 ohm then rises to 1000 ohm after a few seconds. It does appear to have more of a bulge. The one next to it is very higher, 50K. Cap on the other side is ~ 10K. The 10K and the 410ohm are the same capacitor. It is 47uF 35v. I have a 47uF 50V handy. Transistors seem to be around 3.5K and 5K.
 

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Sounds like we may have found the problem. Take out the 47uF 35V (carefully, in case its actually good) and replace it with your 50V guy. Make sure you get the polarity correct, otherwise it will pop too.

After you take it out but before you put the 50V guy in, take another measurement and see what the resistance of the circuit is and what the resistance of the capacitor is.

Like you found, it will take a minute for the resistance to give a reading on the cap, since it is slowly charging it up. Once its done charging, that is the actual value of the resistance.
 

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Discussion Starter #14 (Edited)
The resistance of the circuit is the same with it removed, and the resistance of the cap is high. So I'm not sure if it's really the cap that is the issue.

Edit: I tried it with the new cap, and it does the same thing.
 

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Well crap. When you apply power to the circuit, does pin 7 on the IC switch from high to low or from low to high? (not sure what voltage "high" is, maybe 12V, but "low" should be 0V).

edit: make sure you have a capacitor in there. Either one will do.
 

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Discussion Starter #17
Ok, so now it's working using a 12V power supply. I'm going to be looking at the battery next. Maybe the circuit isn't getting enough voltage. I do know I probably should change it out since some fluid has seeped around the positive pole. It does start and run fine however.
 

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Discussion Starter #19
Sorry for the delay, I was away for several days. I put the old cap in and it worked fine. Well, sometimes it works fine! Other times it seems to want to stay on longer still. However, I think I have some more serious problems. I ended up having to jumpstart the tractor today, and things went downhill from there. After that I had trouble starting it at all, even with another battery I tried. Now it will start, but only if I hold in the shutoff solenoid by hand. I have no idea where that problem came from. I hope I didn't fry something by accident. One of the wires from the alternator plug to the voltage regulator looks like it has slowly fried, and is coming apart. I did get a solid 14v or so at the battery while running though.

There is plenty of suspect wiring in this machine from a previous owner, looks like I have my work cut out for me....
 

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Discussion Starter #20
Can anyone recommend a good make of battery for the 332? I see plenty of talk about 22F for the 318, and the manual has BCI group U1 listed. However I also see posts saying to use a 26R?
 
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