Glow plug switch malfunction

[Diver 6]

I am new to the site because I finally decided after 77 years it was time to give my 9N Ford a rest and upgrade. (Tractor is 77. I'm not there yet). I picked up an L3800 with HST and an FEL. I found an issue today with the glow plug switch. I don't know if all are set up this way but the switch turns to the left for the glow plugs. Problem is it cranks the engine when I do that. Won't fire but it cranks. Turning to the right it cranks right up and runs as it should. This is the only problem I have found. I have not yet looked to see if previous owner messed with the wiring. Will do that tomorrow. Was wondering if anyone has had this issue or if it might just be a bad switch? Also, is there a source for a wiring diagram with wire color detail? Thanks

 

[85Hokie]

I would think that is a bad switch!
Most - as you know of that era, turn left, glow - turn right and start.

Wonder if it wiring issue or contacts doing something weird inside switch!

 

[Jim L.]

Turning the key to the left should not crank the engine.

The Workshop Manual for the L3800 is 9Y121-05200. It has both color codes and wire gauges.

I'll see if I can post a diagram of the key switch.

 

[Jim L.]

Attached jpg file.

B Battery
G Glow Plug
ST Start
AC Accessory

Start goes to the starter relay.

 

[Diver 6]

Thanks 85 and Jim. I'll look at the wires tomorrow and see if they have been buggered with. If not, I'll throw a new switch in.

 

[100 td]

Additionally to above, WSM for L3200 here, it is the previous series but you may glean some info from it, also key switch testing from L3200 may help. Check to see they haven't jumpered wires across the back of the switch, or have them in the wrong place.
http://www.kubotabooks.com/AutoIndex/index.php?dir=Tractor%20Owners%20Manuals/&file=L3200%20WSM.pdf

 

[Diver 6]

Ok, did some digging this afternoon and found that the PO had done some creative wiring. He ran a wire from the glow plug terminal on the back of the main switch to the starter. The original wire to the starter, with connector, was just tucked in free behind the starter. Tested the main switch as best I could with my multimeter (I am by no means an electrical engineer or certified mechanic) and it appears to be functioning fine. My only concern with the switch is there is a jump bar between the glow plug terminal and the empty/unused terminal. Not knowing what the switch looks like in its original condition, I dont know if the jump bar is supposed to be there. Removed the panel and found that the PO had been digging around in there as the relays had been removed from the holding plate. My guess is the starter relay has gone bad and rather than replace it, the PO chose to bypass it by going from the glow plug terminal to the starter. Does this sound correct? I know there is a way to test the relay but it requires adding power to it and testing it which I don't feel proficient enough to do. And does anyone know if that jump bar is supposed to be on the switch? Thanks

 

[North Idaho Wolfman]

At this point I would break down and get the WSM, it will have the wiring schematic and the colors of the wires.
It will also have the procedure to test the start relay.

I'm betting he bypassed the start relay not because it's bad, but because there is an issue with a safety switch that was preventing it from starting.

The bar on the main switch is probably supposed to be there as a lot of switches have them.

 

[Jim L.]

Two attachments, one is the relay diagram, and the other the test for the relay.

The starter relay has coil plus, small Black/Red; coil minus, small Black/White; 12v plus, large Red; and starter motor plus, large Black/White. Cross check the attached photo with these wires to make sure its the correct relay.

You may want to take photos before moving things around, so you can get back to a somewhat working tractor.

I'm with Wolfman. I think that there is more to the story.

It's not that difficult to check the relay. You can always pull just the relay and have someone else check it off the tractor.

 

[Diver 6]

Ok thanks. I have the WSM for it but when it comes to ohms and voltage and electrical relays I'm just not that savvy. ill tinker with it over the next week and update where I ended up. Thanks guys for all the info.

 

[Diver 6]

Thanks Jim. That's probably what I will do. Kubota store not far from me. I'll see if they will check it and go from there.

 

[Diver 6]

The only mod is that jump wire to the starter. So as soon as I figure out if it is the starter relay or a safety switch, I will be able to remove the jump and have it back to factory wiring. Runs great as it is. I just can't heat up the glow plugs cause it cranks the engine. But I am in So. Fla so that has not been an issue in the 80 degree weather.

 

[Jim L.]

Having the starter relay checked sounds like a good plan.

The next diagnostic (don't have to wait for relay check) would be to take the starter relay empty socket and connect a voltmeter to the coil pins, pins 2 and 4. Turn the key to the right for a normal start. When that command is given, there should be 12VDC across those coil pins. This is done without the kludge wire connected between glow plugs and starter relay or relay.

If not, then check fuses. If fuses are OK, then you are now in the safety circuits which control both positive and ground connections.

If you want to post those results, we can keep giving progressive tests to narrow it down.

 

[Diver 6]

I will do that as time permits this week. Thanks for all the great info. You guys are a wealth of knowledge.

 

[rbraeking]

That is actually a glow plug timer relay. My new (to me) L2550 had one that had the smoke let out of it at one time. Since my engine is direct injected I just did not wire the glow plugs when I redid the wiring harness. Any time it is too cold to start without glow plugs it is too cold for me to operate an open tractor. I have attached a large PDF file of my wiring diagram. It shows similar wiring to your picture.

New statement. file is too big for forum limit. If the left turn of the switch cranks the engine then either the switch is bad or the previous mechanic was bad.

 

[North Idaho Wolfman]

That is actually a glow plug timer relay.

You can not compare electrical components across the board for all tractors.
Kubota uses many different systems on many different tractors, sometimes even on the same models.

While your L2550 might have a timer The L3600 does not.

I'm PMing you an email address for you to send me the PDF of the schematic, I might be able to post it, or I can resize and re-post it.

I'm about 90% sure the timer you are referring to is the stop timer, it controls the stop solenoid not the glow plugs.

 

[rbraeking]

You are right. My eyes got crossed. What reason could there possibly be for a timer relay on the stop circuit? Unless power to the stop solenoid puts it in the stop position not run position.

 

[Diver 6]

Had a couple minutes last night to start pulling and testing safety switches. The 2 PTO switches are working fine, clutch switch is fine and seat switch is functioning normal. From reading this forum, it seems the HST switch is notorious for causing problems. That's next as soon as I can get back to it. Just wanted to update. ALSO, does anyone have the L3800 WSM. 100 TD sent me one for the L3200 only which has some differences. I am assuming there is one that incorporates the L3800 as my owners manual list both on the cover.

 

[North Idaho Wolfman]

There is not a free downloadable WSM for the L3800, you would have to buy a copy.

 

[Diver 6]

Well had I known that I would have bought a different model