M1123 possible electrical fire hazard?

BestPrez45

New member
14
10
3
Location
Casa Grande, AZ
Howdy all.
I'm new to the fascinating world of electrical fires on HMMWVs so please hold the chuckling to a minimum.
I was running jumper cables to my M1123 6.5 non turbo batteries trying to get it started. After the WAIT light went out, I flipped the switch to START and nothing but a buzzing from behind the dash and smoke from under the hood. I immediately turned off the switch. Maybe it was on for 3-5 seconds when the smell of burning plastic first hit me. I traced the offending line across the top of the engine block. One end was grounded to a steal bracket and the other end disappeared under what looks like the glow plug control sender. The metal tag on the line reads 54C. I am unable to find reference to this 54C in an online TM I found.
IMG_9325.jpegIMG_9326.jpeg

I guess my questions are this
1) how likely is it that I fried my start box
2) any ideas as to what this fuse is (i'm assuming it's an inline fuse)
3) Is this something I can or want to bypass?

Keep in mind that I do not want to fry like a bacon wrapped hotdog so base any answers off of that desire..... thank you.
 
Last edited:

BestPrez45

New member
14
10
3
Location
Casa Grande, AZ
Howdy all.
I'm new to the fascinating world of electrical fires on HMMWVs so please hold the chuckling to a minimum.
I was running jumper cables to my M1123 6.5 non turbo batteries trying to get it started. After the WAIT light went out, I flipped the switch to START and nothing but a buzzing from behind the dash and smoke from under the hood. I immediately turned off the switch. Maybe it was on for 3-5 seconds when the smell of burning plastic first hit me. I traced the offending line across the top of the engine block. One end was grounded to a steal bracket and the other end disappeared under what looks like the glow plug control sender. The metal tag on the line reads 54C. I am unable to find reference to this 54C in an online TM I found.
View attachment 866636View attachment 866637

I guess my questions are this
1) how likely is it that I fried my start box
2) any ideas as to what this fuse is (i'm assuming it's an inline fuse)
3) Is this something I can or want to bypass?

Keep in mind that I do not want to fry like a bacon wrapped hotdog so base any answers off of that desire..... thank you.
After much searching, this is a 12v Diode Semiconductor device. It started it's life as NSN 5961-01-180-5634, was renumbered a bit later to NSN 5961-01-593-3791. I'll continue searching SS to see if any of this info has already been discovered and posted. Until then, I found a site in germany selling these but they do not appear to ship to the United States. I'll report back with any more updates as they happen.
 

Hummermark

Member
199
15
18
Location
London uk
hi I have one of the BAE systems M1113 they had the same diode ,when I went to view at the New York State facility quite a few had them melted like in your picture including the one I got .
The representative of BAE in charge of the vehicles had obtained new ones which I got 3 with my M1113.
In the zip bag i have with the new ones in has a am general part delivery note to mac motors so he obtained them through them in the USA.
On the paper work it has the NSN of 5961-01-593-3791 same as you have found 👍
But more important for you to get some there is a am general part number of
13013962 they describe it as "coupling assembly"
On the new wire is a yellow tag saying "electrically tested riverside mfg,llc
Hope this is of some use .
If you find out why it is there/what it does could you post?
With a part number if mac does not have it could try kascar in Greenville SC
Or there was a post that you can buy parts from AM general direct.
Although melted everything works fine no damage to any thing? So that why I am curious to why is there ?
 
Last edited:

papakb

Well-known member
2,058
677
113
Location
San Jose, Ca
54C is a backswing diode that's meant to shunt and electrical spike from the IP solenoid turning off to ground keeping it from getting back into the electrical system and damaging more sophisticated electronics, it's surprisingly underrated. A fitting replacement would be a 1N5400 diode rated at 3 amps, 50v PIV with the cathode (banded end) connected to the IP and the anode connected to ground. You can find 10 packs of them on Amazon for under $10.
 

Hummermark

Member
199
15
18
Location
London uk
54C is a backswing diode that's meant to shunt and electrical spike from the IP solenoid turning off to ground keeping it from getting back into the electrical system and damaging more sophisticated electronics, it's surprisingly underrated. A fitting replacement would be a 1N5400 diode rated at 3 amps, 50v PIV with the cathode (banded end) connected to the IP and the anode connected to ground. You can find 10 packs of them on Amazon for under $10.
Thanks for that information👍
Why have the older Humvees not got one i have 6.5 n/a 4speed that does not have it ?or any of the 6.2 that I have had🤔
 

papakb

Well-known member
2,058
677
113
Location
San Jose, Ca
It was probably added as the electronic equipment in the trucks got more and more sophisticated. It's a simple operation to add to any vehicle with a "Y" connection and a short cable with the diode mounted in it. Backswing diodes are very common anywhere solenoids are used because of the big electrical spikes they generate when they're turned off. Early on the MX777 and MX778s were commonly found it tanks where lots of stuff was solenoid actuated.
 

BestPrez45

New member
14
10
3
Location
Casa Grande, AZ
hi I have one of the BAE systems M1113 they had the same diode ,when I went to view at the New York State facility quite a few had them melted like in your picture including the one I got .
The representative of BAE in charge of the vehicles had obtained new ones which I got 3 with my M1113.
In the zip bag i have with the new ones in has a am general part delivery note to mac motors so he obtained them through them in the USA.
On the paper work it has the NSN of 5961-01-593-3791 same as you have found 👍
But more important for you to get some there is a am general part number of
13013962 they describe it as "coupling assembly"
On the new wire is a yellow tag saying "electrically tested riverside mfg,llc
Hope this is of some use .
If you find out why it is there/what it does could you post?
With a part number if mac does not have it could try kascar in Greenville SC
Or there was a post that you can buy parts from AM general direct.
Although melted everything works fine no damage to any thing? So that why I am curious to why is there ?
I know that several members already replied with the technicals and specs for this diode and it's use. I will say my finding out about it's purpose was started on a forum about (AN/MRC-145A ) Comm trucks and they were explaining that this reduced "noise" which I'm assuming means electrical interference in it's equipment.
 

BestPrez45

New member
14
10
3
Location
Casa Grande, AZ
hi I have one of the BAE systems M1113 they had the same diode ,when I went to view at the New York State facility quite a few had them melted like in your picture including the one I got .
The representative of BAE in charge of the vehicles had obtained new ones which I got 3 with my M1113.
In the zip bag i have with the new ones in has a am general part delivery note to mac motors so he obtained them through them in the USA.
On the paper work it has the NSN of 5961-01-593-3791 same as you have found 👍
But more important for you to get some there is a am general part number of
13013962 they describe it as "coupling assembly"
On the new wire is a yellow tag saying "electrically tested riverside mfg,llc
Hope this is of some use .
If you find out why it is there/what it does could you post?
With a part number if mac does not have it could try kascar in Greenville SC
Or there was a post that you can buy parts from AM general direct.
Although melted everything works fine no damage to any thing? So that why I am curious to why is there ?
As for knowing if anything else has been damaged. To that, I do not know as I have not attempted to start again until I found out what this did and had it replaced. I have fingers crossed I didn't take out my smart box.
 

G744

Well-known member
Steel Soldiers Supporter
843
1,133
93
Location
Hidden Valley, Az
Any time a solenoid is activated by DC current (like that one in a HUMMV electrical system) and then turned off or released, a good electrical surge will be sent back upstream. That pulse is not only much higher in voltage than normal, but it is reverse polarity as well. This can damage any device on the same circuit, especially electronic parts.

That is why engineers design in diodes to clamp those pulses.

DG
 
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