L230 glow plug circuit

[Dan in PA]

Hello. Just joined, thanks for having me, and looking for some help. L230 with glow plugs that don't heat. I took the old glow plug module out and hooked it up on the bench and could not get an output so I ordered a new one and replaced with no help. I have a service manual (maybe not the best) with a wiring diagram that I used to hook it up on the bench with a meter and power supply and still no output so I must be missing something. The manual has no theory of operation for the circuit that I can find. The module has 8 pins, hot and ground, one for each glow plug, signal, and feedback. I put 12v on signal on the bench, the machine had 10.5v on that lead with switch on. I'm assuming the feedback is for the indicator. Any advise, theory of operation, or trouble shooting guide would be appreciated. Thank you.

 

[Dan in PA]

After digging thru the manual some more I and looking at the list of fault codes I've realized that the control unit isn't simply an electronic relay but a data controlled switching device that can communicate back to the ecu with health status. This can't be bench tested. Thanks

 

[foton]

there have been people who have bypassed the stock glow plug circuit and added a seperate circuit and switch to heat the glow plugs,not to long ago there was a thread on this subject.

 

[Dan in PA]

Yes, I've had that thought also, takes it back to a simple system. I'm use to working on my old Ford tractors, newest thing I've owned, lol

 

[emilyjohnson85]

If the new glow plug module didn't resolve the problem, there might be something else in the circuit that's off. Check the signal voltage first—10.5V is a bit low, which could be causing the module not to activate. Also, verify all ground connections, as a poor ground can lead to faulty operation. Lastly, the feedback might be crucial in completing the circuit, so ensure that it's properly connected and functional.

 

[Dan in PA]

Thanks for the reply. I can say I don't completely understand the operation of the circuit, not sure I have a problem. I haven't had a starting problem yet but after buying this machine I was going over the basics, I don't want to have to work on it in the winter. When testing the system I hook a meter to one of the glow plugs with the plug hooked up, turn on the key and get a instrument cluster indicator showing plugs on but never get any reading on the meter. Tried it first thing this morning, 53 degrees and it started fine but no reading on the meter. I know I won't see 12volt because of the voltage drop caused by the low resistance glow plug but I should see a few volts. What temp should they come on and what sensor controls it, air intake, or maybe coolant temp sensor? I wish the service manual was better on explaining circuit operation. When bench testing I applied 12v to the signal lead and it didn't turn the circuit on.

 

[foton]

have you tested the glow plugs themselves individually?, they should not read over about 2 ohms each, and I believe that they should get the full 12 volt charge from the battery thru a relay.

 

[Dan in PA]

Yes I did, all were .9 ohms which is in spec per the book. Perhaps your correct about the full 12v, I was just assuming I would see a drop because of the low resistance, but in any case I see 0.00 volts at the plug. Funny thing is with the key off and one of the glow plug leads off I have 5.65 volts on the lead, hook it back on the plug and it goes to zero. Put a current meter on it and no draw. There are codes for shorted and open glow plugs (which I don't have) I'm guessing that how the glow plug module sense's a shorted or open plug. Guess I'll wait till it 20 degrees and see what happens, lol Thanks

 

[haymaker]

On my Bobcat s 510 the plugs come on for about 10 seconds on these 50 degree mornings

 

[Dan in PA]

Hello, still struggling with this. This morning it was 45 degrees and it started but was running rough. Meter shows plugs not come on, I can't think of anything else but chop up the wiring and put in a switch but trying to avoid that. New module, no codes, wires and glow plugs ohm out ok. 12 volts to module for power circuit and ground. The service manual only give repair sequence for trouble codes. Any help appreciated.
Thanks

 

[Dan in PA]

Thanks for taking the time for the in-depth answer. Unfortunately this is not a conventional system with a relay and 12 volt trigger. Instead of a relay it has a module that's a mini computer in it self. It's trigger is pulse width modulated signal from the ecu that commands the module to turn on. There is no bus bar, each plug has it's own wire back to the module, this is how the module monitors each plug for open or short. The module has maybe 8 different possible codes for things like low voltage, high current,etc. (I have no codes). I haven't done a current check because they are getting no voltage but I will do that test with current meter directly to the battery. My guess is there is a faulty sensor that's not throwing a code like maybe ambient temperature. In the end my plan will be to wire them the old fashion way with a solenoid, but trying to avoid that because I will always have multiple code because of the open circuit.

 

[Jim A]

Hook up momentary pushbutton switch from Battery right to glow plugs .Put a 40 amp fuse in . Old foot starter switch from farm tractor can handle 40amps .
Modules ECM s insanity on all new age equipment cost a fortune to replace them . Never waste money on Chinesium aftermarket or used FleaBay electronic components.