HMMWV Glow Plug Specs, Properly sizing a fuse

[MatthewH]

Working on finishing the wiring on my 6.2l swapped M37.
Having trouble finding the specs on the stock 24v HMMWV glow plugs, to properly size a fuse for the main hot wire to the solenoid.

Here's my layout

2- group 31 batteries under the pass seat, 4 ga wire ran from the batteries to the glow plug solenoid under the hood. The solenoid is activated by a M35A3 start switch, which uses a standard military circuit breaker to receive power.

Would really like to add a fuse just off the batteries to protect the feed wire incase of incident, but unsure of a proper size. Gut says 50amp should do it, being 24v should draw half the amps of the 12v counter part, and seems the general consensus is they draw 10amps.

But rather have it right then guess.

Thanks

 

[MarcusOReallyus]

Probably not much need for getting an accurate reading here. Since you are protecting the feed lines against a short, and there is a properly sized (?) circuit breaker downstream, I suggest you go 15 or 20 amps above the circuit breaker's rating. You can rely on the CB to protect everything downstream of that, and you don't want your main fuse blowing before the CB trips.

If you use mega fuses, it's pretty easy and not very expensive to change your mind on the fuse size.

 

[MatthewH]

What I ended up doing is running a short wire from the battery to a 80amp Maxi Fuse holder under the seat with the batteries. Then run my wire from there threw rubber heater hose threw the cab to the solenoid.
No idea if this works yet. Like the rest of this project, everything takes forever and still haven't been able to get to running it yet.

 

[Augi]

The resistance of those glow plugs is about 2 ohms when new.

Ohms Law is V=I*R

You know V=28 max (when the alternator is charging) and I just told you R

Rearrange and solve:

I=28V/2OHMS
I=14A

So you should size for 8 glow plugs at 14A each plus some overhead (usually 20 or 25%).

So you may want to fuse for 125A to 140A.

Augi

 

[MatthewH]

The resistance of those glow plugs is about 2 ohms when new.

Ohms Law is V=I*R

You know V=28 max (when the alternator is charging) and I just told you R

Rearrange and solve:

I=28V/2OHMS
I=14A

So you should size for 8 glow plugs at 14A each plus some overhead (usually 20 or 25%).

So you may want to fuse for 125A to 140A.

Augi

This is exactly what I was looking for. Thank you so much for this info. Won't be hard to change out the fuse holder, I had bought one that uses a small bar style fuse, and they start at 100amp and go up from there
Again, thank you