Power to the glow plugs

I have a 1960 McCormick International tractor with the diesel engine.
The glow plugs quit last summer. I finally had the time to fix them and got a set. I replaced all four of them and cleaned the wires and other contacts with sandpaper and contact cleaner. Put everything back together and they still don't work.
Now, the problem is that there is power going to all four glow plugs. Whether the key is turned off or on there is power to the glow plugs.
I thought, OK,there would be if they were grounded when you needed them by rotating the switch on the dash.
I tried rotating the switch on the dash and there was no change in power. No resistor on the dash turning red or anything.
With the key off or on there is still power to the glow plugs. BTW 12.9 volts at the front plug and 12.4 at the rear plug.
Is everything OK and it's just a lack of understanding on my part or do I have a problem?
Thanks.

(quoted from post at 17:41:00 07/06/19) I have a 1960 McCormick International tractor with the diesel engine.
The glow plugs quit last summer. I finally had the time to fix them and got a set. I replaced all four of them and cleaned the wires and other contacts with sandpaper and contact cleaner. Put everything back together and they still don't work.
Now, the problem is that there is power going to all four glow plugs. Whether the key is turned off or on there is power to the glow plugs.
I thought, OK,there would be if they were grounded when you needed them by rotating the switch on the dash.
I tried rotating the switch on the dash and there was no change in power. No resistor on the dash turning red or anything.
With the key off or on there is still power to the glow plugs. BTW 12.9 volts at the front plug and 12.4 at the rear plug.
Is everything OK and it's just a lack of understanding on my part or do I have a problem?
Thanks.

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We really need to know the model number of the tractor, and maybe the engine make. A 4 cylinder helps, but not enough. If we give information for a series type and it is parallel it would be wrong. Jim

It's the 144 c.i.d.four cylinder diesel. The glow plugs are wired as original, in series. Power is strongest at the front of the engine and
weakest towards the rear of the engine but still above 12 volts.

There, maybe that's a tad better.

Hi Bob, you have a British built B-275 Diesel same glow plugs as B-414 and many others BUT someone could have modified it over the years and install new fast heat glow plugs that are 12V in parallel not in series like the original ones.

Could you please post a picture of the left side of the engine with the glow plugs. Does it have the L-handle switch and indicator resistor on the dash?

JimB

A series circuit glow plug is going to have 2 terminals on each plug. The battery voltage goes for the dash indicator/switch, to the rear plug from that plug to the next toward the front. The front plug will have its output grounded. Each plug is designed for about 1.7 to 2 volts each. There is a total system failure when any one plug filament/heater fails.
If there is 12v or so on your plugs, they must be parallel. One wire goes from plug to plug with each plug grounded. Each of these has a 12v designed heating element. (might be rated at 9 volts actual running voltage) The fact that you are reading 12ish volts at each plug when they are not "on" is a problem. The real switch should cause zero voltage at the plugs when the system/tractor is off. If it has voltage at the connection to each plug, it could be a bad ground at the battery causing a meter reading that is not real. If in fact that reading is between each glow plug terminal and a real ground at the chassis, and on all the time, the glow plugs would overheat and fail. if you take the wire off of one glow plug and measure resistance between the plug terminal and ground (on the lowest ohms setting) it should read fractions of an ohm. If it has very high resistance, in hundreds of ohms, or infinity, it is a bad glow plug.
If they were series plugs the resistance to ground with both terminals disconnected would be infinite resistance (open) but between the terminals the plug would be reading a fraction of an ohm.
Fixing the cause of voltage where there should be zero is task number one. Determining other faults and bad plugs is #2
Jim

(quoted from post at 11:41:00 07/06/19) I have a 1960 McCormick International tractor with the diesel engine.
The glow plugs quit last summer. I finally had the time to fix them and got a set. I replaced all four of them and cleaned the wires and other contacts with sandpaper and contact cleaner. Put everything back together and they still don't work.
Now, the problem is that there is power going to all four glow plugs. Whether the key is turned off or on there is power to the glow plugs.
I thought, OK,there would be if they were grounded when you needed them by rotating the switch on the dash.
I tried rotating the switch on the dash and there was no change in power. No resistor on the dash turning red or anything.
With the key off or on there is still power to the glow plugs. BTW 12.9 volts at the front plug and 12.4 at the rear plug.
Is everything OK and it's just a lack of understanding on my part or do I have a problem?
Thanks.

Click to expand...

Your tractor left the factory "positive ground".

With the voltage readings you are getting, it would seem you are using the "ungrounded" battery (-) terminal as the reference point for your voltage readings.

Glowplug circuit is pretty basic, current flows from (-) battery terminal to a terminal on the ignition switch (30), (glowplug current isn't switched by the ignition switch) and from that terminal to the glowplug switch (34), passes through resistor/indicator (33), and on to the 4 glowplugs connected in series.

Hi Bob, Thanks for the photos. The key switch only controls power to dash gauges and the generator charging circuit.
The Glow plug switch on the dash will always work with key switch ON or OFF.

Your glow plugs appear to be the correct originals and wired properly. You did the outer to outer inner to inner wire pattern with the insulator in between?

NEVER APPLY 12V DIRECTLY to ANY ONE GLOW PLUG OR IT WILL GO POOF AND BURN ITSELF OPEN.

With reference to your photo that I added 2 arrows and colored a wire:
Using the engine block as the ground reference, when the glow plug switch is held on the voltage at the first glow plug where I put the red arrow should be around 6V and each glow plug should have about 1.2V voltage drop across it. The voltage at the red arrow at the front plug should almost be 0V as that wire I colored red is the ground to the engine block.
With the glow plug switch on:
If you get 0V volts at the first arrow then most likely the Indicator resistor on the dash is open/burnt out.
If you get 12V at the second arrow by the front of the engine then there is a problem with that highlighted red wire that goes to the engine block to supply the ground.

As I mentioned earlier these glow plugs are new. I replaced them and wired them the same as they were before. first and second plug are connected by the wire with the big ends as are the third and forth cylinder. The second and third cylinder's plugs are connected with the jumper wire with the small ends.
The battery was changed over from two six volt batteries to one big 12 volt battery. I couldn't find two matching 6 volt batteries when I needed them and I got a good deal on the big 12 volt battery.
Going by what you said, grounding to the block and touching each plug produced nothing. Holding the "L" switch down, also, produced nothing at the first plug. Key on, nothing. Key off nothing. So I may be alright and just need a new dash indicator/ resister. Correct?

You were correct about my readings. All I was showing was that I had a fully charged battery. I put one probe on the negative (-) post of the battery and , essentially, grounded to each of the plugs telling me It had a tad over 12 volts showing in the battery. It done this anywhere I could touch with the probe. My bad!

Bob, before replacing parts and since you have a VOM, using the other BOB's wiring picture then check the voltage from frame ground to both sides of the dash indicator, one side should have 12V when the glow plug switch is ON and if no 12V work back to glow plug switch. Anything could happen to the wiring on these old tractors.

We had an early B414 big brother to the B275 and it had 2 x 6V batteries as well and we converted it to a single 12V battery. These tractors were originally +Positive ground with generators but over the years they were converted to -Negative ground to use Delco alternators.

According to my B414 OP's Manual wiring diagram, the wire from #4 glow plug(back of engine) to Glow Plug indicator is Brown/Green, Glow Plug indicator to glow plug switch is Brown/Yellow,
Glow plug switch to Starter Solenoid is Brown/Red, there is another connection from Glow plug switch to Amp meter is Brown/Green.

Hope this helps
JimB

Thanks for the help everyone. I'll get back here with what I find tomorrow.

Those original style plugs run at around 1 volt, not 12 volts. If you get an over 12 volt reading, it is because they are drawing no power.
You have something hooked up wrong or your test is invalid. A voltage reading with no load is kind of meaningless.

The tractor has five glow-plugs all run in series. The four the engine and the 5th open-coil plug in the dash that is your indicator. All five have the same resistance and all 5 heat up at the same rate. This way, when the open-coil in the dash glows - so do the other 4 in the engine. Each one is rated to work on 1 volt. If they actually had 12 volts they were burn up instantly.

You are MUCH better off installing modern burn-out proof 12 volt plugs run in parallel (Bosch makes them for Mercedes diesels). They work great. With the original system like you have now - just on bad connection or one fail plug - and nothing works.

This is the old series hook up like you have. Five resistors all hooked in a row in series dropping 12 volts down to 1 volt at each plug.

This is what the new 12 volt plug looks like and how it gets hooked in parallel.

Here is another view of a B275 switched from the 1 volt plugs in series to the 12 volt burn-out plugs in parallel. I used an indicator bulb in the dash to replace the 5 indicator glow coil it came with originally.

(quoted from post at 20:18:46 07/06/19) This is what the new 12 volt plug looks like and how it gets hooked in parallel.
<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto28723.jpg">

<img src="https://www.yesterdaystractors.com/cvphotos/cvphoto28724.jpg">

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And here is it's younger cousin, a "424" with Bosch Duraterms and a GM 6.2 diesel glowplug controller, making GP operation automatic.

Ok, I am completely rewiring my 1968 IH500 with what I believe is the BD154 engine. The glow plug indicator is trashed and I am wanting to convert to the Bosch 80035 plugs that everyone is talking about seeing how I can not replace it. I am a little confused about the wiring though.

1. Do I need a relay and if so can you share a part number with me? Also can you tell me what wires go where for this part of the system? I am thinking that the Relay gets its power from the hot lead behind the dash and then delivers it to the plugs when the glow plug button is pushed that switches on the relay? I just need some reassurance that I am correct and not going to burn the whole thing up.

2. I kinda understand parallel vs series wiring but I want to be sure so that I do not screw it up worse. Right now they are in series so the wire goes from glow plug button to the indicator/resistor in the dash and then to the rear plug (+) and then from the rear plug (-) to the 3rd plug (+) and then from the 3rd plug (-) to the 2nd plug (+) and then from the 2nd plug (-) to the 1st plug (+) and then the 1st plug (-) is grounded to the frame or engine. When I wire the new plugs I should go from the glow plug button directly to all 4 plug (+)? Then are the plugs automatically grounded to the block with the threading because they do not appear to have a place for a second wire?

3. What gauge wires should be used in each location?

I am mechanically inclined but wiring something from scratch is relatively new to me.

I would greatly appreciate any help that you can give.

Thank you,
Marc