Wait to start light flashing

[asesso]

I have a 1990 hmmwv that I recently purchased. It usually shows an amber wait to start light that goes out after a few seconds and the engine starts immediately. Today for the first time the light flashes then goes out and the truck easily starts. Why has the light started flashing. Do I need a new control box? I currently have a black Narteon with a yellow label.If I need a replacement what would be a good choice?
Art

 

[Greg89]

Art,

I have a 1990 hmmwv that just started to do the same thing when I installed a new Nartron S3 box. Mine also starts just fine after the blinking stops. Have you been able to determine the cause?

Greg

 

[papakb]

Almost all of the PCBs behave differently with regards to the "wait to start" LED. That activity is also affected by the outside temperature and engine temperature and the way the Glow Plug Controller or Temperature Sensor (depends on what box you have) interacts with the PCB. There's a lot of confusion about what sensor goes with what PCB but a quick search will turn up charts with those combinations listed.

Kurt

 

[Action]

I thought that if the light blinks, then something is wrong. Either gone bad or mismatched parts.

 

[joeberg]

Greg,

Did you have an S3 prior to installing the Nartron S3? I had a 1993 that had an S3 and mine would blink 14 times before going out. I replaced my TSU with a yellow band from Kascar ($25) and it resolved my issue and it works perfectly now. Previously I had a silver band TSU. I suspected they didn't replace my TSU when they installed an S3 which caused the error code. Prior to the TSU replacement, I tried replacing my glow plugs which didn't help in my case.

 

[WalterMitty]

Is it typical when it's really warm for the light to not come on? It's been 80's and 90's where I am at, and I haven't noticed the light ever coming on. I've only owned the thing since late June, so it's never been cold weather here yet.

 

[Action]

My light comes on on a cold engine even when the heat index is over 100. You can let it sit for several hours, and the engine will still be warm enough to not activate the plugs.

 

[WalterMitty]

I've let it sit a couple of days, and the still haven't noticed the light coming on.

 

[86humv]

Greg,

Did you have an S3 prior to installing the Nartron S3? I had a 1993 that had an S3 and mine would blink 14 times before going out. I replaced my TSU with a yellow band from Kascar ($25) and it resolved my issue and it works perfectly now. Previously I had a silver band TSU. I suspected they didn't replace my TSU when they installed an S3 which caused the error code. Prior to the TSU replacement, I tried replacing my glow plugs which didn't help in my case.

KDS S3 uses a yellow striped TSU, 6500398 and the Nartron S3 uses a plane silver with black top TSU, 12469158-2 which crosses over to 6500398.
Both brands [ KDS and Nartron ] have the same NSN on box and tsu.

 

[joeberg]

KDS S3 uses a yellow striped TSU, 6500398 and the Nartron S3 uses a plane silver with black top TSU, 12469158-2 which crosses over to 6500398.
Both brands [ KDS and Nartron ] have the same NSN on box and tsu.

I have read that the Yellow striped TSU works with both KDS and Nartron S3 models. My TSU must have been bad. It was a silver label with a Nartron S3, replaced with a yellow label and works perfectly now. Thanks.

 

[1 Patriot-of-many]

Is it typical when it's really warm for the light to not come on? It's been 80's and 90's where I am at, and I haven't noticed the light ever coming on. I've only owned the thing since late June, so it's never been cold weather here yet.

Yes, it will flash really quick once. At least on mine it does when the temp is higher than about 70 degrees

 

[Retiredwarhorses]

Yes, it will flash really quick once. At least on mine it does when the temp is higher than about 70 degrees

NO....outside temp will not affect the operation of the glow plug system on a completely cold motor.
the TSU senses coolant temp....if it's below 120deg or so....it's going to cycle the glow plugs.
my GP's have cycled on 100deg days on a truck previously driven to events and later started, say several hours and the GP's cycle. If the temp is correct and does not require cycling, then it will just flash for a split second.

 

[1 Patriot-of-many]

Sure it will. When your HMMWV sits in a pole barn at 70 degrees for a week the coolant is going to be 70 degrees(actually gets much hotter inside the pole barn than ambient temp outdoors and so the coolant would too), ...... Mine doesn't energize the glow plugs above 70 degrees or so. Guess my mileage varies... I can't imagine my coolant is getting up to 120 degrees, but that's what you and the troubleshooting guide says. Maybe the TSU's changed somewhere down the line?

 

[Action]

Sure it will. When your HMMWV sits in a pole barn at 70 degrees for a week the coolant is going to be 70 degrees(actually gets much hotter inside the pole barn than ambient temp outdoors and so the coolant would too), ...... Mine doesn't energize the glow plugs above 70 degrees or so. Guess my mileage varies... I can't imagine my coolant is getting up to 120 degrees, but that's what you and the troubleshooting guide says. Maybe the TSU's changed somewhere down the line?

My guess is that something is wrong with your system. How long do you crank it at 75 degrees, if the wait light does not come on?

 

[1 Patriot-of-many]

About 3-5 seconds tops. When it's cooler, it functions just like it's supposed to, comes on for about 7 seconds, starts almost instantaneously.

 

[Action]

I'm no expert, but it cranks for a long time because the plugs are not on like they should be.

 

[1 Patriot-of-many]

Okay, I getting weird behavior, Yesterday I turn the switch to on, get the quick flash from the wait light. Crank for about 5 seconds, it starts. I turn it off, wait a couple seconds then turn it on again, wait light does what it's supposed to, about 7 seconds on. Then starts immediately. Did it again, same thing proper operation........Is my TSU the culprit?, and what does the light on the top of the TSU signify? Seems to be always on.

 

[Action]

, and what does the light on the top of the tsu signify? Seems to be always on.

what ???

 

[1 Patriot-of-many]

what ???

Green light on the top of the tsu is on all the time, what does this light mean

 

[Retiredwarhorses]

Green light on the top of the tsu is on all the time, what does this light mean

you might want to post a picture...there is NO green light on a TSU.