1 more glow plug idea

Talked to a IHC mechanic and he thinks there was a resister bar on the ammeter to cut volts to 6 for the glow system only. I tried wiring a 6 volt battery to the switch and indicater and the indicator took 20-30 secs to glow red. Anyone got an ammeter to look at? Part # 708109R93 subs to a 528211R1. Thanks, Don from Canada

Most ammeters I am familiar with, if they had a resistor on them, were part of the ammeter circuit, to shunt current past ammeter, so it didn't carry full current flow. Ammeters carry current through themselves, and measure amount flowing through instrument.
If there's a resistor in the glow plug circuit, it is probably a separate resistor.

not sure what your working on. the old 6.2l chev diesels used 6 volt glow plugs with a relay to cycle them on and off so they would not burn out with 12 volts. i believe it was only 5 or 6 sec. at a time they cycled.

Had a 6.2 chev bought military glow plugs higher voltage lasted very well just needed to recycle more in real cold weather

It might have been attached to the ammeter, but it would not have been part of it..otherwise, it would affect everything on the tractor.
So it would have been between the ammeter and the glow plug switch.
Just as a side comment, the older Mercedes Cars with the 4-cylinder (example, 180D, 190D, 200D, 240D[up till 1976 or so) had the same system, at least from your description. There was a separate resistor in series with the glow plug circuit. There would have been a different one for a six cylinder engine with the same plug.
If you can find a mercedes parts specialist, he should know what you are talking about.
Later Mercedes used the ceramic-tipped full-voltage plugs and were wired in parallel, not series, and there were kits to retrofit the older vehicles. They heated a lot quicker than the old ones.
You could convert your tractor the same way.

Radio Shack used to sell wire wound dropping resistor to run 6volt stuff in 12 volt car

looked like a 6 inch long brown tube with slider on outside to get voltage exactly where you want it, had legs to mount it

can't find that part on Radio Shack website

but when they convert 6v tractors to 12v, they add a resistor to the coil to keep it from cooking

that resistor ought to work

I have a B275 which uses the same glow plug system. I replaced the glow plugs a couple years ago, and its still working just fine. Takes about 10 - 20 seconds for the indicator to start to glow on 12 volts. If its glowing faster on 12 volts, you still have a problem with the glow plugs or a short in the wiring somewhere.

There is NOT an extra resistor between the common terminal on the ammeter and the glow plug indicator. The glow plug system is intended to work directly off 12 volts.

Are you absolutely certain you have the glow plugs themselves wired right? Do you know if the plugs are getting hot? If the indicator is getting way too hot too quick, there has to be a short somewhere, or you have the wrong indicator.

Start at the top of the glow plug closest to the indicator (the rear of the engine). The lug from the wire to the indicator should be directly under the thumbscrew, then a metal cap, then a ceramic insulator about 1/4" thick, then the wire to the next glow plug. The next plug should have two wires, one to each adjacent glow plug, separated by the 1/4" thick ceramic insulator, and so one for the other two plugs.

Do you have a voltmeter? If so, connect it between the top lug of the rearmost glow plug (the terminal that connects to the glow plug indicator) and ground, then turn on the glow plugs. What does it read?

I just went out and checked mine. With the indicator glowing, there is about 4.5 volts between the glow plug terminal fed by the indicator and ground. If yours shows something less, either one or more glow plugs are shorted or or they're wired wrong, or they're the wrong glow plugs.

Keith

All you'll do with an ignition ballast resistor in the glow plug circuit is melt the resistor. Point type ignition coils draw about 3 or 4 amps...the ballast resistor is sized to provide six volts drop with that much current flow.

The glow plug system draws several tens of amperes (don't remember the actual number off the top of my head - 60 amps comes to mind, but I'm not sure that's right) and will rather quickly overheat a ballast resistor designed for 3 or 4 amps.

Keith


Keith