Glow plugs and resistor

Hoka Hey · Nov 12, 2006

My TL 2700 is suffering from a no start problem. This has been on going since I bought it a month ago. I now know that it is not an air in the lines issue, but it is a glow plug issue. I received three new plugs, one had been tested before leaving the supplier. I put them in my tractor. It fired for the first time since I have owned it. Then nothing. I pulled the plugs and tested them and they are not heating up. But, I believe they heated up the first time I tried to crank the tractor over. It was 35 degrees out when the tractor fired and before it wouldn't fire in 60 degree weather. The plugs only markings are "9V"...no part numbers. I assume this means 9 volts? Can my tractor be delivering too much voltage and burning up good glow plugs in 20 seconds of heating? They don't look burned. Is there a resistor? My supplier said there is no way my tractor could burn up the plugs that fast, but hey are also shocked that three new plugs are bad. I agree. Any wisdom to share on this problem? I am afraid to put three new plugs in just to fry them in a few cycles.

EFC · Nov 13, 2006

There is a resister in the dash, it is what glows when you activate the glow plugs.

Buck

mopacman · Nov 13, 2006

If one glow plug shorts out it will keep the others from heating up. Put a volt meter on the bar that hook between the plugs and the other test lead on ground. the volt reading should be about 9 volts. If the voltage is lower than 9 volts their is a shorted plug or a bad connection in the circuit to the plugs. If the voltage is higher then 9v one or more plugs is open. Larry

Hoka Hey · Nov 13, 2006

Thanks guys, My tractor doesn't have the resistor that glows on the dash. It has a bulb that lights up when you hold the key to the left to activate the glow plugs.
Larry, what do you mean by the the plugs are open? If one plug is bad the others won't heat? Thanks for the help! Erik

EFC · Nov 14, 2006

If you have a dash light then you have a TL2701?

Buck

mopacman · Nov 14, 2006

If a plug is open it will have a high resistance reading on a ohm meter. It will not draw any curent to make heat. The most common cause of this would be the heater circuit in the plug burnt into or open. If a plug is shorted the electrical circuit in side the plug would weld it self to the case of the plug. This would cause the electrical power to go stright to ground and would not leave any power for the other plugs to make heat. I have not seen a circuit that uses a light bulb. cant help on that. It well either have a resistor or a power supply to provide the 9 volts.

Hoka Hey · Nov 14, 2006

Thanks Buck and Larry
The tractor is stickered and was sold to me as a tl 2700. It is a 1990, 4 wheel drive, pto is activated by a dash switch. I don't know if this points to a TL 2701? Hopefully I can make some progress. Would you suggest I look any where for a resistor? Will 12 volts burn up the plugs in 20 seconds? Erik

mopacman · Nov 14, 2006

The books say not to put 12 volts on them to test them. I would say the resistor is under the dash or the side panels whare the fuses are or the hand throttle is. On my tractor it is easy to follow the wire back to the resistor. Larry

Hoka Hey · Nov 27, 2006

Okay, my tractor IS a TL 2700f. At some point it was determined that the resistor in the dash wasn't needed, so they installed the light bulb indicator. The light bulb isn't a very effective resistor, so I am getting 12 volts to my 9volt glow plugs...and frying them.
Does anybody have a photo of their TL series tractors dash? I need to know where the resistor goes. The bulb is located in the plastic gauge cluster at the bottom right. Is this where the glowing resistor lives? Or, is the plastic gauge cluster not the correct location due to the heat of the resistor? Erik

gemini5362 · Nov 27, 2006

You could burn it open possibly with 12 volts in a matter of seconds. I would start looking for other things. Does it have a fuse in line with the voltage to the glow plugs. If it worked once and then does not again that sounds like a blown fuse. Sometimes glow plugs have fusible links. That is a piece of wire that is smaller than the wire that goes to the plugs. When there is too much current it burns up. I looked at the glow plugs on my kubota b6200 and the glow plugs are connected in parralel meaning that the wires go to the connection on the glow plug all at the same time. The other poster was right a shorted glow plug would drop the voltage down on all of them if that happened. I think if a glow plug shorted to ground that you would see physical indication of that. If one glow plug opens that should not affect the others. The first thing you need to do is to connect a voltmeter to the top of the first glow plug with aligator clips then turn the key to the glow plug position and see if there is any voltage there. If there is and it is 12 volts get a resistor. I would get the one for the other tractor that uses them and put it in line with the wire going to the first glow plug. If your tractor is like my kubota the wires are daisy chained. ( wire from switch to first glow plug, wire on top of the wire at first glow plug goes to second. etc etc ) Make sure to put this resistor somewhere that it wont touch anything flammable since it gets red hot. That should solve your problem. I would first off though make sure I did not have a fusible link or a fuse that would be my first thing to troubleshoot.