Bad news big repair

[rScotty]

I’m getting .58 volts from ECU to the GP relay right now. It’s 30 degrees. Problem is, I don’t know what voltage I should be getting from ECU?

You need some way to get normal values. Is there any way you can get values from a functioning M135x or similar tractor?

Normally I'd say that a glow plug relay needs 12 volts and a reasonable current just to actuate, but that woud also be more volts and amps than I would expect the ECU to provide directly.

So the glow plug relay could easily be a duplex type where a small voltage relay triggers a larger relay to carry the high current for the glow plugs. I would expect it to be 12 volts, but it could be less with a duplex setup.

Without normal values, or another tractor to measure, or some sort of spec sheet I don't see how you can figure this out in a reasonable amount of time.
Have you called the a big dealer like Messicks to see if they test ECUs?

BTW, you asked what some of us do for a helper. I took a 50 foot extension cord, cut off the plugs, and put alligator clips on one end and a toggle switch on the other. That way I can activate or measure a circuit from a distance. Sometimes that helps... a helper is better.
rScotty

 

[WranglerX]

Umm... exactly where a

I’m getting .58 volts from ECU to the GP relay right now. It’s 30 degrees. Problem is, I don’t know what voltage I should be getting from ECU?

Where are you measuring the .58 volts..... On a typical relay there should be 12 volts on one side of coil (85?) and to operate relay other side of coil needs a ground (86?)... If the operate path from ECU is at .58 volts it would appear to be providing a ground to operate relay... OR it could be you are missing the 12 volts on input voltage side of relay or a open winding in relay.....

Typically most automotive (yes tractors too) use a really basic relay as in image below...

Applying 12 volts and ground to 85 and 86 should cause rely to operate and switching "common" contact from "normally closed" to
"normally open" ...You need to be measuring voltage(s) on both sides of relay input (coil)..

In the case of putting power to glow plugs I would guess (no wiring diagram to reference) that you should see 12 volts on "common" (30) and wire to glow plugs on "normally open" (87) ...

Good quality relay should have a diagram of how it operates stamped into case...

Disclaimer is this is "typical" not necessarily exact for you application...

 

[CADplans]

I’m getting .58 volts from ECU to the GP relay right now. It’s 30 degrees. Problem is, I don’t know what voltage I should be getting from ECU?

That 0.58 volts (or even 4 volts for that matter,,,) is the MAIN reason you need access to an analog meter,
These stray voltages in electronics fool novice mechanics all the time, a digital meter always shows the weird voltages.
The analog meter usually requires enough current to move the needle to consume that erroneous voltage.

A similar thing that these digital meters see is voltage constantly bouncing around.
The analog meter is difficult to make the needle bounce.

The way to insure you know what voltage you need is to look at the relay, it may (should?) have the voltage listed.

One way to eliminate the stray voltage is to have a very minor load on the circuit being tested,,
If you get an car interior lightbulb, and connect the bulb between the test point and ground, the stray voltage will go away.
Some low resistance (high ohms) value resistor would be even better than the bulb.

 

[WranglerX]

Actually best way to eliminate possible problem with relay is to remove it from tractor and bench test it.... Not energized you should see continuity between 30 and 87a, with relay energized (12 volt & ground on coil) you should see continuity from 30 to 87....

 

[Hay Dude]

The .58 was measured with ohm meter in the wire connection from ECU to connection on relay. There are 2 relays.
I haven’t done much with relays, other than replacing since, working on my international dump truck 10’years ago.
Turning plenty of wrenches, but I haven’t had to deal with much electronics for many years….which I guess is a good thing.
Done for today. Chewing up way too much time/profit, so it looks like a spring loaded switch will be the final answer.
Many thanks to the mature, helpful responses.
To those of you who think I did this for “drama”, I have no idea where you get that from? Hope you find happiness and satisfaction in it though?
To me it was just like any other request for help in solving a tractor related issue. To a few others I guess it wasn’t?
My intention from original post was to fix the EXISTING system FIRST, if possible. Then move on to the easy way out (manual switch).
To all those who suggested a block heater thanks, but There’s no power where the tractor is left to plug it in.
Will update with any final findings and end results

 

[Hay Dude]

Actually best way to eliminate possible problem with relay is to remove it from tractor and bench test it.... Not energized you should see continuity between 30 and 87a, with relay energized (12 volt & ground on coil) you should see continuity from 30 to 87....

Did that
All good

 

[LouNY]

Well heck here goes;

Terminal layouts

The automotive ISO mini relays above are typically available in two types of pin layout designated Type A and Type B layouts. These layouts are shown on the two 5-pin relays below (pin 87a not present on 4 pin relays):

Terminal/Pin number	Connection
85	Coil
86	Coil
87	Normally Open (NO)
87a	Normally Closed (NC) - not present on 4 pin relays
30	Common connection to NO & NC terminals

Per what has been posted here it is a possibility that your ECM is providing the ground for the relay coil either T85 or T86.
One way to verify that would be a voltage check of the relay base with the key turned on check for voltage on T85 or T86 of the relay socket,
if you have voltage on either of those then the ECM is providing the ground for the coil.
While the relay is removed you can look for voltage on T30, T87 or (T87A not likely) if so the system is good to the relay.

Also you could disconnect the battery and using an ohm meter check from the relay(s) from T87 to the glow plugs for continuity,
it may be T30 but normally that would be battery power but I have seem T87 used for power and T30 to the powered device.

If your system does not have the ECM grounding the relay coil with one side of the relay coil having voltage present whenever the key is on,
then one of those terminal T85 or T86 should be going to ground.

This link has a lot of good information on relays;
Automotive Relay Guide | 12 Volt Planet

Have fun.

Edited to correct numbering error,
Lou

 

[LouNY]

I see that there were several posts while I was pecking away on mine.
One other thing not knowing the system 4 glo plugs could be a good load on one relay with 2 in the system they could have split it and done 2 per realy.

 

[bearthebruce]

If the ECU is grounding the relay coil, then the ground to the ECU must be a good ground capable of carrying the relay current, the wire to the relay must be good capable of carrying the relay current, and the transistor in the ECU must be good, capable of carrying the current. One of the best ways to test all that is to use a trouble-light. Take a dash indicator lamp, wire one side to the +12 and the other touch to the wire that goes to the ECU. When triggered, the light should light.

I also read a bunch about the triggering event. I agree with the poster who said get some freeze spray. Something like this: https://www.amazon.com/Professional-Freeze-Electronic-Component-FR-777-777/dp/B000Z99ZCA

If you know where the temp sensor is located, you can spray it and force the glow plug circuit one should think.

Any chance you have a wiring diagram?

 

[5030]

I know one thing for certain, never buy a relay from a dealer. Had to renew the ac blower relay last year on my M9 and called the dealer (had the catalog number off it in hand). My cost from the dealer was 79 bucks which I considered highway robbery so I crossed it on DigiKey and Dell Electronics. Dell was less so I actually ordered a couple, just in case. The cost at Dell was 7 bucks each.