Nartron S3 Smart Start Almost Left Me Stranded

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Augi
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Nartron S3 Smart Start Almost Left Me Stranded

Post by Augi » Tue Jun 16, 2020 12:14 am

It also damaged my starter so now I need to pull it and rebuild it.

Long story short, there are 5 automotive style PCB mount relays in the box. The one that engages the starter solenoid welded shut and held the starter on permanently.

It's my partially my fault for not paying attention. I was parked in a pullout and started the truck and immediately pulled out onto a state highway at 50mph. After 10 - 15 minutes I smelled what I thought was horridly burning brakes so I pulled over. As the truck came to an idle I heard what sounded like a box of rocks rolling around in the transmission and I thought I was in for the big one...

So I switched the engine off and it quit firing but to my surprise continued to crank! That's when I realized something was probably up in the S3 box. I quickly raced around to the other side of the truck and removed the battery positive cable. I carry the TM's in the truck so a quick glance through the schematic in the back of the -20 and I decided to disconnect the 74A wire from the starter relay. I reconnected the battery and the starter was no longer cranking (so the starter solenoid itself wasn't welded). I measured the voltage on the wire and it showed +24v without turning the start switch to crank.

Fortunately the starter wasn't totally hosed (that's a testament to how beefy it is) and after letting it cool a bit I was able to restart the truck and drive home. Conveniently the starter solenoid is also connected to a pin in the STE/ICE connector by the shifter. Shorting pin S and pin T will bypass the S3 box and crank the starter directly. So no lying on my back trying to short the terminals with a screw driver.

A second "partially my fault" but also kind of a saving grace: For a couple of years now the truck has intermittently had a "click-no-start" problem. Maybe 1 in 50 starts it won't crank even after a couple of tries. So I made a little jumper for the S and T pins in the STE/ICE connector to carry in case I need to force it. Turns out that was the relay giving a warning that the contacts were burned. Eventually they arced and welded.

I haven't pulled the starter to open it up yet but I expect the bendix is shot and maybe the rotor shaft bushings need replacement. It still starts the truck OK but it's just louder and angrier sounding.

I couldn't have a dead-lined truck in the driveway and the S-T jumper isn't layman (read: wife) friendly so I pulled the S3 box to confirm the welded relay. Turns out Nartron used Song Chuan brand relays (I didn't know they could do that in a defense product) at roughly 1/5 the cost of Japanese. After identifying the offender I removed and de-lidded it to find the weld.

Image

I replaced the dead relay with a Panasonic, buttoned the box back up and now she worky just fine.

On a side note, to get to the back side of the relays you have to de-solder the main connector from the board and it requires a TON of heat. I used a 240W soldering gun and it was still a slow process. Getting the relay off was also a pain. This board has huge power traces and the copper pour is thick.

Image

Augi


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86humv
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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by 86humv » Tue Jun 16, 2020 10:51 pm

Thats a KDS box.
Here's a Nartron and a KDS ....
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Image
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Kurt Lesser
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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by Kurt Lesser » Wed Jun 17, 2020 6:16 pm

Hey Cam, maybe we should start a business "upgrading" the KDS boxes! Isn't that another ChiCom relay peaking out on the Nartron PCB too?
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86humv
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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by 86humv » Wed Jun 17, 2020 7:19 pm

It has a stinkin chineze one also...but the big one is USA
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milcommoguy
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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by milcommoguy » Wed Jun 17, 2020 7:22 pm

From the other Cam... They all use them. Taken a few apart. Another not so smart box bites the dust, CAMO

Augi
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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by Augi » Wed Jun 17, 2020 9:32 pm

Well I stand corrected. KDS it is.

As for upgrading these things... I never want to take one apart again.

There's nothing interesting in there and it's a bear of a de-soldering job :\

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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by Kurt Lesser » Thu Jun 18, 2020 8:53 am

Yes, but when a box costs $300, $400, 500 or more I'm sure guys would be more than happy with a $150 repair.
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US Navy, 1969-1975
M996A1 Ambulance w/M101A3 Trailer
M274A2 Mule
M151A1 Mutt w/M416B1 Trailer
M890 Crew cab

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Re: Nartron S3 Smart Start Almost Left Me Stranded

Post by milcommoguy » Thu Jun 18, 2020 3:31 pm

I get the entrepreneur, build a better mouse trap... and in this hobby experience it can work. Bumpers, tops, mounts, upgrades, sales of NOS parts, reproductions, etc. Nuts and bolts.

Hmmwv with its simple electrical system and add in the overly complicated electronics to start a truck already prone to known failures takes on a WHOLE new perspective for a business model supporting the hobby. Risk and liability. Guess I am a party pooper.

That all sound good and make a buck or two at it. Electrical parts sales or repairs could be and idea??? Until the something else fails and I/ME/YOU get the blame for another set of glow plugs, a starter or worst, burns down YOUR truck.

My first (and last) box took a crap and after an hour with the prints, I built and designed one to be NOT be so smart. A one off or two, fully functional drop-in, plug & play replacement. Totally simple, repairable and no issue after 4 years of use in my rig. NO cheap O parts and risks I control and willing to take.

Now if it was 1986 and the government was paying... I would be right in there. CAMO

sale, Sale, SALE


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