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#21 ·
A resistance test will not tell the full story, A single strand of wire will show near zero resistance, but when you try and pass a reasonable current through, say 8-12 amps, the wire will go up in smoke. Relay contacts can show continuity and still not be able to pass the current required to run the load, in this case, the Glow plugs. If you have enough slack in the wiring harness, you could do a voltage check at the two large solder lugs. With the key on, there should be about 12 volts at one terminal at all times and about 12 volts on the other lug for as long as the relay is clicked in, on my 1026R about 5 seconds.
 
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#22 ·
OP has done the test of measuring voltage at the glow plugs. There isn't any. He has also said he heard the relay click on and click off 20s later. That sounds like everything before the relay is probably working. The relay sounds like it is working (the click). Since power isn't getting where it needs to go, that probably means the contacts are bad. Depending on how bad they are, it might be easy to see this with an ohmmeter or the ohmmeter might say things are okay when they really aren't.

I would guess the relay is bad if that is good enough for the OP no further testing is necessary. I give a money back guarantee on my diagnosis. If it doesn't work, I will give you back what you paid me for it 😏
 
Discussion starter · #23 ·
So I am going to teach (or try to) how to test the relay before i unsolder it. If it looks to be bad i will wait to see if the guy at digikey has a direct fit , If not i'll order the fugi. They guy at the electronic store mentioned using a small jumper wire and seeing if i get voltage at the glow plug, or yes using a voltmeter to see if i get 12v in and 12v out on the lugs. i just have to look at the schematic and see if i can figure out what pin is what.

i will be monkeying around in the next few days.

thanks !
 
#28 ·
When I bought my 96 455 it had over 1600 hours on it. I discovered that the previous owner had replaced the fuel shutoff solenoid but had wired the pull in coil directly to a 12v source. This lasted about an hour after I got it home when it finally burned out the solenoid. More inspection showed that the pull in circuit no longer worked at all. Also, mice had done a real number on much of the wiring. It’s ugly and will be a big job to rewire the whole tractor. But I needed to get this thing working so I installed a manual fuel shutoff with a choke cable. Also, the glow plug circuit was hosed, so I added a separate momentary switch directly to the glow plugs. It’s working and the 455 is giving me great service. But now I may take the time to rewire it and may also have to rebuild the diesel control module circuit board. Fun times ahead and I’ll be very interested in your progress.
 
Discussion starter · #29 ·
Kind of a long story ....I had ordered a relay and while waiting for it to come in the mail I started tinkering with things..(not the best idea I guess when you don't know totally what you're doing) I tried applying 12v across the terminals for the coil and a trace shorted out in like a millisecond.
As I had mentioned earlier i have a 96 and in the manual I was looking at the diagram for the older style diesel control module and I had the two relays backwards. So I ended up frying the trace for the fuel solenoid.

Anyway fixed the trace ( checked continuity etc) and went to test the board on the tractor to see if the relay still clicked and noticed the fuel solenoid didn't kick on . With key on I could feel the relay for the solenoid click and the glow plug relay did not.
Went to double check the relay clicks and saw smoke. It turns out a transistor at the top of the board fried / melted.

The odd thing is a couple months ago when I was talking with the guy at the electronics store trying to match the relay up he pointed out that it might not be the relay and pointed to the transistors and told me these can go bad too.

Apparently transistors send signals to relays etc (?) so i don't know if the transistor had been bad all along causing the relay not to work or if it was just the relay , or both. Maybe when I applied 12v I fried something out. ???

I ended up buying a new board and everything is fine, other than being a bit embarrassed telling this story.....
(Maybe it will help someone out ??)

I have the old board and if I can match up the transistor i will still try to fix it as I am 99% sure I have the correct relay (the relay frog more had sent me in this thread).

It turns out one of the new guys at work used to fix boards in his previous job and he checked some things put and thought maybe a new transistor and a relay may fix it. I have already shelled out the money for the relay and then the new board so a transistor and my time aren't much at this point. A spare would be nice to have.I will post back if it gets fixed I just won't have time for a while as I am painting the inside of my house.
sorry for being long winded, and thanks to everyone for their input.

If anyone needs a pic of the p/n for the relay or any questions i will reply back.

thanks,
chris
 
#34 ·
Yes, the relays worked, I actually replaced them both chasing the issue. Then I figured out that power for the pull in circuit is it's own wire to the board, just because the board and relays have power does not mean the pull in circuit has power. That wire had a break in it, likely shorted to the radiator in the past, repairing that wire solved my problem.
 
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stevecaylor
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