How to bypass PCB? I am aware some HMMWV owners have done it. TOBASH

[TOBASH]

H1 is 12v and it’s not uncommon to burn up glow plugs over time…so, no…this will not stop glow plugs from eventually failing.
The H1 uses AC60g’s but unfortunately uses a spade tip, as far as I know, there is no 12v bullet type GP.
You can use 12v on a regular Hmmwv glow plug.

My concern is NOT blowing out plugs.

My concern is swelling. 12V seem to do it less,

IMHO

Also easier to find 12V at NAPA last minute, for when I forget to call the awesome people at Kascar, HPG, etc….

 

[Retiredwarhorses]

My concern is NOT blowing out plugs.

My concern is swelling. 12V seem to do it less,

IMHO

Also easier to find 12V at NAPA last minute, for when I forget to call the awesome people at Kascar, HPG, etc….

glow plugs swell, even the so called “non-swell”
Even some splatter the size of a grain of sand will cause a plug to fight to come out.
Like I said, the issue is the the bullet tip type GP, and may I remind you…you’re scenario is one that lends you’re thought process as if the truck will not run with bad glow plugs, of course you know it will and it will just be stubborn to start, but you only need a glow plug or 2 to make that happen…so IMHO, this 12v thing is not worth the effort, especially since you all tell everyone that the box will never fail and you won’t
Fry glow plugs cuz your finger in the controller….this is a solution to a non-problem me thinks.

 

[Humpty]

Two things.

First, decreasing voltage to the glow plugs will increase amperage. I'd think the likelihood of swollen glow plugs would increase with them drawing *more* amperage.

Second, are you guys really laying on your glow plugs? I hit mine for 1 mississippi 2 mississippi 3 mississippi 4 mississippi and she pops right over down to 25 degrees or so.. colder than that and I'll repeat the 4 count and off she goes. My glow plugs are all fine. No swelling. I've made it a point to frequently check them because I run the dreaded Chinese cheapos that i'm told are prone to swelling up to roughly the size of a kielbasa - but a year in of daily driving and they still look fine.

I feel like the janky "smart boxes" are more likely the culprit to swollen glow plugs rather than voltage.. and perhaps the pulsing cycle they like to do after the engine starts.

BONUS 3rd thing ... according to my AM GENERAL troubleshooting guide, the HMMWV glow plugs ARE 12v glow plugs running on 24v.

 

[JimiT]

Two things.

First, decreasing voltage to the glow plugs will increase amperage. I'd think the likelihood of swollen glow plugs would increase with them drawing *more* amperage.

Second, are you guys really laying on your glow plugs? I hit mine for 1 mississippi 2 mississippi 3 mississippi 4 mississippi and she pops right over down to 25 degrees or so.. colder than that and I'll repeat the 4 count and off she goes. My glow plugs are all fine. No swelling. I've made it a point to frequently check them because I run the dreaded Chinese cheapos that i'm told are prone to swelling up to roughly the size of a kielbasa - but a year in of daily driving and they still look fine.

I feel like the janky "smart boxes" are more likely the culprit to swollen glow plugs rather than voltage.. and perhaps the pulsing cycle they like to do after the engine starts.

BONUS 3rd thing ... according to my AM GENERAL troubleshooting guide, the HMMWV glow plugs ARE 12v glow plugs running on 24v.

You are right. Timing is key! That's the reason I built in that timer module, set it to four seconds. Make it fool-proof... You can not go wrong with it.

 

[Humpty]

You are right. Timing is key! That's the reason I built in that timer module, set it to four seconds. Make it fool-proof... You can not go wrong with it.

My concern with the timer is engine temp. It can be 25 degrees out, if I go to Walmart, spend 45 minutes inside, I don’t need the glow plugs to heat the cylinders to restart. She’ll pop right off with a quarter turn of the engine. In fact, I really only need the glow plugs for the first start of the day - and then only if the outdoor ambient temperature is below something like 70 degrees. In the summer months the glow plugs are pretty much not needed at all. I think thats the brilliance of the manual controller. The simplicity. Adding a timer really only adds a potential failure point.. and in an instance where you’re just shutting your truck off to order at a drive thru, restarting to pull up to the window, shutting off, restarting.. what i’m respectfully calling a “dumb” timer (because the timing cycle happens regardless of engine temperature) could do more damage than good.

 

[JimiT]

My concern with the timer is engine temp. It can be 25 degrees out, if I go to Walmart, spend 45 minutes inside, I don’t need the glow plugs to heat the cylinders to restart. She’ll pop right off with a quarter turn of the engine. In fact, I really only need the glow plugs for the first start of the day - and then only if the outdoor ambient temperature is below something like 70 degrees. In the summer months the glow plugs are pretty much not needed at all. I think thats the brilliance of the manual controller. The simplicity. Adding a timer really only adds a potential failure point.. and in an instance where you’re just shutting your truck off to order at a drive thru, restarting to pull up to the window, shutting off, restarting.. what i’m respectfully calling a “dumb” timer (because the timing cycle happens regardless of engine temperature) could do more damage than good.

The timed glowing circle happens only when you manually push the "glow button". If the engine coolant temp and/or the ambient temp is warm enough, you don't need to push it. Just to be clear: in my version the glow plugs are engaged only when you push the button. The role of the timer module is only limit the time (currently set to the safe 4 seconds) while the glow plugs are getting power after the button has been pushed. Fool prof. Even if you push the button for 20 seconds continuously or push it seven times in a row, the glow plugs will be engaged only for 4 seconds, so you cannot fry/blow up your glow plugs. You can see it on the video I published.

 

[Humpty]

The timed glowing circle happens only when you manually push the "glow button". If the engine coolant temp and/or the ambient temp is warm enough, you don't need to push it. Just to be clear: in my version the glow plugs are engaged only when you push the button. The role of the timer module is only limit the time (currently set to the safe 4 seconds) while the glow plugs are getting power after the button has been pushed. Fool prof. Even if you push the button for 20 seconds continuously or push it seven times in a row, the glow plugs will be engaged only for 4 seconds, so you cannot fry/blow up your glow plugs. You can see it on the video I published.

Firing the glow plugs only when manually activated is far more reasonable. It could come in handy if you loan your vehicle out to friends or family members or if it were in a fleet situation. For a single operator it seems like just another potential point of failure unless you lack the physical dexterity (or mental aquity) to press and hold a switch for 4 seconds.

 

[TOBASH]

Place a weebasto and never need glowplugs.

 

[theovenguy]

I purchased my 2008 M998 in November 2023. Two brand new batteries later and it ran without any hiccups whatsoever. I decided to install a keyed ignition to significantly reduce the possibility of any stranger’s unauthorized use of the vehicle. (I also added a magnetically activated reed switch to the trigger wire as a further safeguard against bypassing the keyed ignition.) During this process, one of my conductors fell out of my hand and grounded out - quite dramatically ! I didn’t disconnect my batteries, and that let the smoke out of my PCB, so thank you for this post, Tobash, and for the community’s collaboration as well. I‘m anxiously anticipating the resurrection of my ’green turtle’. I also acquired a nearby helmet top Humvee over the summer at a great price, thinking it was a wise investment for potentially needed parts. Its PCB was already removed before it came to me, so I’d like to know where I could find a dead box(or two) to rebuild OR at the very least a source for the aviation cable type connection into the box. Happy New Year to everybody here on the forum

 

[Humpty]

I purchased my 2008 M998 in November 2023. Two brand new batteries later and it ran without any hiccups whatsoever. I decided to install a keyed ignition to significantly reduce the possibility of any stranger’s unauthorized use of the vehicle. (I also added a magnetically activated reed switch to the trigger wire as a further safeguard against bypassing the keyed ignition.) During this process, one of my conductors fell out of my hand and grounded out - quite dramatically ! I didn’t disconnect my batteries, and that let the smoke out of my PCB, so thank you for this post, Tobash, and for the community’s collaboration as well. I‘m anxiously anticipating the resurrection of my ’green turtle’. I also acquired a nearby helmet top Humvee over the summer at a great price, thinking it was a wise investment for potentially needed parts. Its PCB was already removed before it came to me, so I’d like to know where I could find a dead box(or two) to rebuild OR at the very least a source for the aviation cable type connection into the box. Happy New Year to everybody here on the forum

The big one going to the engine harness (9 pin with 3 big fat pins in the center) I believe is a AMPHENOL Circular panel Connector Straight Plug 9P 97-3102A-20 97-3102A-20-9S

the smaller one going to the dash (8 pin) should be an AMPHENOL 206433-1

These are from the notes I made when I was thinking of building a new start box from scratch. I ended up reusing the connectors on my wonky start box so never bought new connectors.. but googling those part numbers they *look* right.

 

[theovenguy]

Thank you, Humpty - for your thoughtful post regarding the connectors on the PCB.
Your suggestion led me to look in a place that helped in deciphering the nomenclature for the plugs’ respective configurations, so I ordered the following items:

The nine pin connector into the engine bay is a 97-3102A 24-11P.
The eight pin connector from under the dash is a 97-3102A 22-23P.

If I am wrong and these do NOT mate with the existing chassis connections on the Humvee I will update this post with the corrected inforation.

 

[Humpty]

Thank you, Humpty - for your thoughtful post regarding the connectors on the PCB.
Your suggestion led me to look in a place that helped in deciphering the nomenclature for the plugs’ respective configurations, so I ordered the following items:

The nine pin connector into the engine bay is a 97-3102A 24-11P.
The eight pin connector from under the dash is a 97-3102A 22-23P.

If I am wrong and these do NOT mate with the existing chassis connections on the Humvee I will update this post with the corrected inforation.

Hope they pan out. Now and then guys get these trucks with no boxes at all or end up with boxes so cooked the connectors are unusable. Knowing what those part numbers are would be a HUGE help to those folks. Yeah, I know you can buy a $800 box and be done with it, but for those of us who are handy with basic hand tools (and are saving up for hard doors) building our own boxes is not just fun but significantly less expensive.

In my situation my truck started draining my battery over a few days and at first I was thinking of just building a box from scratch so I wasn't completely immobilizing my truck while I was ironing out my build... but then it quit cycling the glow plugs and the weather started getting colder so it was pretty much immobilized anyway haha so I said the hell with it and dug in. 100% glad I did. The manual start box is absolutely the way to go.

 

[kboy]

I've just built the manual glow plug control box, from TOBASH diagram w/ minor modification. The Wait-light pin (E) on dashboard connector needs GND to light up. So, I connected it to relay pin #85 (the gnd side of relay, which is connected to the GlowPlug push button) rather than relay pin #86. Wait light illuminates when GlowPlug push button is pressed.

 

[TOBASH]

I've just built the manual glow plug control box, from TOBASH diagram w/ minor modification. The Wait-light pin (E) on dashboard connector needs GND to light up. So, I connected it to relay pin #85 (the gnd side of relay, which is connected to the GlowPlug push button) rather than relay pin #86. Wait light illuminates when GlowPlug push button is pressed.

The dashboard wait light only tells you you activate it. My light tells you whether or not you have any functional glow plugs

 

[DFink]

The dashboard wait light only tells you you activate it. My light tells you whether or not you have any functional glow plugs

Finishing up a manual glow plug controller per your diagrams/ parts list and have a question. The dash side connector Pin E will have +24V on it going to the Wait to Start light. I am thinking of replacing the wire to the coil side of the solenoids and placing the wire from Pin E to the glow plug solenoid output and changing the wires to the WTS LED. That way it should only light IF the 2nd solenoid is actively putting out 24VDC.
Good idea, bad idea?

Thanks for the schematics!

 

[Humpty]

View attachment 942018
Finishing up a manual glow plug controller per your diagrams/ parts list and have a question. The dash side connector Pin E will have +24V on it going to the Wait to Start light. I am thinking of replacing the wire to the coil side of the solenoids and placing the wire from Pin E to the glow plug solenoid output and changing the wires to the WTS LED. That way it should only light IF the 2nd solenoid is actively putting out 24VDC.
Good idea, bad idea?

Thanks for the schematics!

The WTS light *is* +24v, grounding it makes the light light. I and others have just added a small 24v relay so when your glow plug solenoid is activated that relay engages and sends the WTS to ground. That will indicate you have (at least some) voltage going to the glow plugs.

 

[TOBASH]

The WTS light *is* +24v, grounding it makes the light light. I and others have just added a small 24v relay so when your glow plug solenoid is activated that relay engages and sends the WTS to ground. That will indicate you have (at least some) voltage going to the glow plugs.

The schematic as posted shows an LED that will only light up if you have at least one working glow plug.

If you want extra credit, you could go under the hood and put LEDs on all of the glow plugs

 

[DFink]

The WTS light *is* +24v, grounding it makes the light light. I and others have just added a small 24v relay so when your glow plug solenoid is activated that relay engages and sends the WTS to ground. That will indicate you have (at least some) voltage going to the glow plugs.

Yes, I was planning on rewiring the WTS with a permanent ground and using the existing wire from Pin E to supply the voltage. If the solenoid were to weld closed I would have an indicator. It's just me expecting the worst possible outcome.

 

[Humpty]

The schematic as posted shows an LED that will only light up if you have at least one working glow plug.

If you want extra credit, you could go under the hood and put LEDs on all of the glow plugs

I had briefly considered (very briefly) using an embedded ESP32S3 to monitor individual glowplug resistance and operational voltage along with fuel, engine temp, oil pressure, etc in a single gauge but decided that was way overkill. If the WTS light lights, it's getting juice.. if it doesn't pop on chilly mornings, none of the glow plugs are left alive.

 

[wjeeper]

Been replicating kboy's/ TOBASH's diagrams. Thanks a million for posting all this info up!

Background: My smart start box was sitting on the floorboard and the harness was chopped instead of being disconnected when I picked it up from Yermo I brought all all the chopped wires ends into a small Harbor Freight water tight box. All the splices are under the sheet of aluminum and the relays are mounted via nutserts. I mounted the box on top of the footwell for ease of wiring and future serviceability:

(Ignore the 60 amp circuit breakers, leftovers from another project, just used for mockup)

Its always bothered me that there are no fuses/breakers. I am adding 3 to the system to ease my mind with the higher amp items. Currently I am connecting the following from the engine side of the harness running to breakers:

• Terminal D (wire 575A, 24v to glow plugs)
• Terminal F (wire 5B, 24v Run HD engine electrical)
• Terminal E (wire 81A , 24v source always hot)

(The relays are 24v, 200A)
If one were to add circuit breakers, what amperage would be appropriate?