How many amps do the glow plugs pull at full load?

[TOBASH]

How many amps do the glow plugs pull at full load? All 8 together in Winter, worst case scenario?

Thanks,

T

 

[doghead]

Found on the inter webs. Erik’s

A working glow plug should draw approximately 12 - 15 amps at 24 volts DC.


You said “worst case”, well battery voltage is also a variable.

 

[Curtisje]

When the key is turned on and the wait light comes on the system starts pulling 12 volts at 126 amps. As the cycle continues the amps steadily drop down to 88 amps when the cycle ends and the wait light goes out. With the wait light out the rest of the system is pulling 5 amps.

I measured this with a 400 amp meter. My glow plug system draws from a 24v to 12v converter, not the stock resistor bank.

I live in the desert so the temperature wasn't as low as your asking. It was 40-50 here when I tested them. The system went through the full cycle.

 

[98G]

When the key is turned on and the wait light comes on the system starts pulling 12 volts at 126 amps. As the cycle continues the amps steadily drop down to 88 amps when the cycle ends and the wait light goes out. With the wait light out the rest of the system is pulling 5 amps.

I measured this with a 400 amp meter. My glow plug system draws from a 24v to 12v converter, not the stock resistor bank.

I live in the desert so the temperature wasn't as low as your asking. It was 40-50 here when I tested them. The system went through the full cycle.

Good data either way, but what vehicle did you measure this on?

 

[Curtisje]

Oops. My M1028 CUCV. I didn't realize this was a HMMWV thread.

 

[Milcommoguy]

Doctor... Hmmwv not all grease, nuts and bolts. A couple of variables at work here. Electrical Resistance and Voltage a thing called OHMS LAW.

So we know a good glow plug has a resistance in the range of 1.5 to 5 Ohms. Age, temperature, design, etc. Let's pick 3 ohms as the average.

OK, say 8 good glow plugs, averaging 3 Ohms each. Calculate for resistance in parallel > https://www.allaboutcircuits.com/tools/parallel-resistance-calculator/

Answer = .38 Ohms a very small resistance. Call it the "cold resistance"

Next measure battery Voltage. Easy to do, but gets a little tricky here. Another variable. Our nice strong batteries measure 28 Volts. For academics sake let's stick with the 28 Volts, knowing under a hard loading it will drop. Flakey batteries could drop to ZIP so ours are really strong.

So at this very moment / instance we energize the circuit apply the law. > https://www.allaboutcircuits.com/tools/ohms-law-calculator/

BAM... 73.68 Amps of in rush current. All the variables are in effect. Voltage is coming down, hot glow plug resistance going up working to turning those electron in to quick heat in the resistive element.

I did it for Ya. Considering the best and worst case for the plug range stated above 1.5 Ohms for all and 5 Ohms for all (not a likely scenario)

Here the results using our super duper batteries at 28 Volts (could be real world) and hitting the plugs cold.

The lowest resistance plugs 147.37 Amps. The higher resistance plugs 44.44444444 Amps. And that if the voltage stays the same. Not likely here too.

Try this... juggling the variables or work it out with say a burnt out plug or two. (zero Ohms) Try with a weak battery voltage, say 22 volts. Going to be hard to get the HEAT and then run the STARTer er er er.

It's all about them Ohms and Volts, and a little grease. It's all an balancing act.

Not a doctor, but play one on S.S. CAMO

This quarantine thing is getting to me. Going to take a pill now

 

[TOBASH]

Thanks Cam.

I will report back to you about any success/failure/explosions/meltdowns once I receive the Cole Hersee parts.

If successful I will post.

Ciao