m998 Solenoid Wire ( 74A ) Hot All The Time

[knighthawk]

I have a 1986 M998 that the starter solenoid burned out on. I replaced the solenoid and starter with a good used unit. When I hooked the batteries back up the starter engages and tries to start the engine. The problem is that wire ( 74A ) to the starter solenoid is hot all the time the batteries are hooked up even with the ignition switch in the off position. The ignition switch is working correctly ( tried a spare with the same results). At this point I suspect the power control box but I do not have a spare to try. Am I missing something or should I go ahead and order a replacement PCB ? M998 with a 6.5 and 200 amp alternator if it makes a difference.

 

[Dock Rocker]

You don’t happen to have a keyed ignition switch do you? That is the culprit many times.


Sent from my iPhone using Tapatalk

 

[knighthawk]

No it is the stock ignition switch. Wire 11A is hot with the batteries connected. 29A gets power when switched to run and 14A gets power when switched to start. Checked with a meter and verified by changing out switches.

 

[86humv]

Ign. switch out "S" should be 14A to Neutral sw.In...then Neutral out should be 14B to Smart start in socket "A".
Smart start out in eng. compartment is Pin " I " to wire 74A to solenoid.
......................
Disconnect batteries, ...unplug under dash connector on Smart box.
Then reconnect batteries.....and with Ign, sw. off...check socket A on dis-connected harness.....should be no voltage until you turn Ign. sw to start [ with neutral sw. on shifter engaged.

 

[papakb]

You can also measure the "start" signal on circuit 74 on pin "S" of the STE/ICE connector.

 

[knighthawk]

86humv, Per your suggestion I checked the dash connector on the smart box. I have no power to socket A in any position , i.e. no voltage in the off, run , or start positions.

 

[86humv]

86humv, Per your suggestion I checked the dash connector on the smart box. I have no power to socket A in any position , i.e. no voltage in the off, run , or start positions.

Make sure your shifter is in neutral.
If nothing.....You can also disconnect it under truck and see if your getting voltage to the switch.

 

[BennyM1097A2]

Hello at all. My Name is Benny from Germany. Sorry my english is not so good. I have the same problem with my humvee....74a is allways hot. All switches are ok. I hope anybody can help me.

M1097a2 from 1992, 6.5 with 4l80

 

[TOBASH]

If you have a keyed ignition, it has failed. Aftermarket keyed ignitions fail and can fuse in the “start” position.

Alternatively might be a PCB issue. You can rebuild the protective control box with the posted plans.

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

I'm not trying to speak sacrilege here, and I don't want to precipitate a war of words. :shock: How might I build a manual control box? My 24Volt Landcruiser just uses a glow wire to show glow plugs are ready, and then she just starts right up with the twist of a key. Civilian 6.2 Diesel...

www.steelsoldiers.com

 

[BennyM1097A2]

Hello. Its the original start switch, its testest and ok. I have the box bypassed....same problem....

 

[Milcommoguy]

Alternatively might be a PCB issue. Depending on the model, manufacture... there is a slave relay driving the starter solenoid lead 74. Might be welded close?

Might be time to get a new box, CAMO

 

[BennyM1097A2]

My box is bypassed.....same problem....i have no lights, no blinker, nothing too.....

 

[Milcommoguy]

It's a little hard to trouble shoot over the internet not knowing one's skill set and tests made. This is a very simple one wire circuit to engage solenoid. All I can offer up... AND I think you're up to it... is double check the single wire lead 74A and follow it from starter solenoid back to the engine connector. Have schematic in hand and walk it back to the source or where it is coming from. (I think you are working it )

A little more detail to "have no lights, no blinkers and nothing ?? study the drawing, make logical measurement or in your case bypassing to get some clarity. Might have to sleep on it... and new thoughts of the goings on will POP into one head with the Ah ha moment.

I have more questions than answers... so not much help in the help department. A picture of the engine and body connector could be helpful. I have had customers with rusted, busted ones and broken wires.

No quickie answers here... HumV sometimes HarD, CAMO


If that 74a lead is hot + 24 and a ground return to batteries good... solenoid should be engaged and starter should be spinning. Need more data.

GOOD LUCK

 

[BennyM1097A2]

It's a little hard to trouble shoot over the internet not knowing one's skill set and tests made. This is a very simple one wire circuit to engage solenoid. All I can offer up... AND I think you're up to it... is double check the single wire lead 74A and follow it from starter solenoid back to the engine connector. Have schematic in hand and walk it back to the source or where it is coming from. (I think you are working it )

A little more detail to "have no lights, no blinkers and nothing ?? study the drawing, make logical measurement or in your case bypassing to get some clarity. Might have to sleep on it... and new thoughts of the goings on will POP into one head with the Ah ha moment.

I have more questions than answers... so not much help in the help department. A picture of the engine and body connector could be helpful. I have had customers with rusted, busted ones and broken wires.

No quickie answers here... HumV sometimes HarD, CAMO


If that 74a lead is hot + 24 and a ground return to batteries good... solenoid should be engaged and starter should be spinning. Need more data.

GOOD LUCK

Tank you.
So one day i want to start my humvee. I turn ignition to run and the starter works.....i find out the 74a is hot all the time. So i checked the start switch, its ok. Than i get the 74a away from the starter and turn ignition to run, no lights wotking, no blinker, no horn too. Than i bypassed my box....same.problems....i dont know what i schould do now. Maybe my harnes is grilled????? But i can not see any grilled section on it and it dont smell....

 

[Milcommoguy]

Tank you.
So one day i want to start my humvee. I turn ignition to run and the starter works.....i find out the 74a is hot all the time. So i checked the start switch, its ok. Than i get the 74a away from the starter and turn ignition to run, no lights wotking, no blinker, no horn too. Than i bypassed my box....same.problems....i dont know what i schould do now. Maybe my harnes is grilled????? But i can not see any grilled section on it and it dont smell....

Jumping right in... again

A little deeper dive into this. I see your 4 post and last reference to a like problem was 2019. Not all problems generally are the same to be "shotgun" fixes... but the info surrounding them could be a clue. Research is golden.

Breaking it down... (from your statements and tests with my translation to HumV talk, limited knowldge and LOTS of questionable assumptions)

So one day, U want to start THE humvee. U turn ignition to run and the starter works. So, I take it the truck started. Starter did not disengage and it was freak-out time. Q, what did you do to clear that ? It can happen biased on a bad switch, some control boxes with slave start relays, stuck solenoid and those darn Gremlins . This is why we the jump to these parts out of the gate. Could be bad. Quick fix...maybe? And did we learn anything?

Trying to keeping a clear mind to the confusion. My option... the harness in the HumV is very robust under normal conditions. For it to source 24 volts to wire 74a on its own... not likely, but tests will quickly verify if grilled or toasted. Time for Mr. Volts & Ohms.

Again... schematic in hand is you road map to success. Basic input and outputs of the controller are shown with a bit of deciphering with a magnifying glass and thinking what the heck they were trying to do. There are the letter pins of connectors to work back to the wire numbers and the functionality of the whole gizzmo. This is going to be very helpful when "ringing out" the harness.

Next... whats going on with the BYPASSING ? Did you open the box and wire a hack to get a work around? (good idea in some situations) I would be helpful to know which box model you have. and what happen in there. Are there any NON-standard add-on's and fill in the blank _____________. This happens a lot, only to find out OH YEA, I got this key fob, remote, long range security doggie thing... after going down the "rabbit hole"

Sometimes a problem is staring one in the face and just not seeing it. Help is here and maybe get a buddy to take a look-see too.

Maybe not be the fix your looking for...but here across the pond and getting my feet wet.

A story of and's..........

SO to END "You'er the boots and eyes on the prize, CAMO GOOD LUCK and GOOD LUCK

 

[AAVP7]

Benny, where in Germany are you located ? Maybe we can find an experienced Humvee owner close to you.

Also, not trying to lure you away from this great and indispensable forum, but we have a german-language forum under HMMWV-Forum.de . Maybe it is easier for you to describe your steps in your native language.

About your problem: With weird problems like this, I would always start with the basics, and work along then. Are you definitely sure your batteries are healthy and fully charged ? Weak batteries create very strange effects sometimes. It´s not enough to hold a multimeter to the battery terminals, and get 12.x volts. The battery needs to be put under a substantial load, and still have good voltage. The very minimum load for this would be to switch high beam lights on.

 

[BennyM1097A2]

Benny, where in Germany are you located ? Maybe we can find an experienced Humvee owner close to you.

Also, not trying to lure you away from this great and indispensable forum, but we have a german-language forum under HMMWV-Forum.de . Maybe it is easier for you to describe your steps in your native language.

About your problem: With weird problems like this, I would always start with the basics, and work along then. Are you definitely sure your batteries are healthy and fully charged ? Weak batteries create very strange effects sometimes. It´s not enough to hold a multimeter to the battery terminals, and get 12.x volts. The battery needs to be put under a substantial load, and still have good voltage. The very minimum load for this would be to switch high beam lights on.

Benny, where in Germany are you located ? Maybe we can find an experienced Humvee owner close to you.

Also, not trying to lure you away from this great and indispensable forum, but we have a german-language forum under HMMWV-Forum.de . Maybe it is easier for you to describe your steps in your native language.

About your problem: With weird problems like this, I would always start with the basics, and work along then. Are you definitely sure your batteries are healthy and fully charged ? Weak batteries create very strange effects sometimes. It´s not enough to hold a multimeter to the battery terminals, and get 12.x volts. The battery needs to be put under a substantial load, and still have good voltage. The very minimum load for this would be to switch high beam lights on.

Hello thank you, i am.in south germany in Bavaria, near landshut an munich.

 

[BennyM1097A2]

Jumping right in... again

A little deeper dive into this. I see your 4 post and last reference to a like problem was 2019. Not all problems generally are the same to be "shotgun" fixes... but the info surrounding them could be a clue. Research is golden.

Breaking it down... (from your statements and tests with my translation to HumV talk, limited knowldge and LOTS of questionable assumptions)

So one day, U want to start THE humvee. U turn ignition to run and the starter works. So, I take it the truck started. Starter did not disengage and it was freak-out time. Q, what did you do to clear that ? It can happen biased on a bad switch, some control boxes with slave start relays, stuck solenoid and those darn Gremlins . This is why we the jump to these parts out of the gate. Could be bad. Quick fix...maybe? And did we learn anything?

Trying to keeping a clear mind to the confusion. My option... the harness in the HumV is very robust under normal conditions. For it to source 24 volts to wire 74a on its own... not likely, but tests will quickly verify if grilled or toasted. Time for Mr. Volts & Ohms.

Again... schematic in hand is you road map to success. Basic input and outputs of the controller are shown with a bit of deciphering with a magnifying glass and thinking what the heck they were trying to do. There are the letter pins of connectors to work back to the wire numbers and the functionality of the whole gizzmo. This is going to be very helpful when "ringing out" the harness.

Next... whats going on with the BYPASSING ? Did you open the box and wire a hack to get a work around? (good idea in some situations) I would be helpful to know which box model you have. and what happen in there. Are there any NON-standard add-on's and fill in the blank _____________. This happens a lot, only to find out OH YEA, I got this key fob, remote, long range security doggie thing... after going down the "rabbit hole"

Sometimes a problem is staring one in the face and just not seeing it. Help is here and maybe get a buddy to take a look-see too.

Maybe not be the fix your looking for...but here across the pond and getting my feet wet.

A story of and's..........

SO to END "You'er the boots and eyes on the prize, CAMO GOOD LUCK and GOOD LUCK

hello camo. many thanks for your response. Unfortunately the humvee won't start. because I don't have electricity anywhere. not even on the injection pump. Nothing works at all except the starter. It turns as soon as I switch to the run position. I bypassed the kds box like I found on the internet because I thought the box was the problem. But it didn't help, the problem still exists.

As soon as I switch to the run position, the starter turns, the brake light lights up and the transmission light lights up and the instruments work. Otherwise there will be no power to the entire humvee.

Many greetings, Benny

 

[Milcommoguy]

hello camo. many thanks for your response. Unfortunately the humvee won't start. because I don't have electricity anywhere. not even on the injection pump. Nothing works at all except the starter. It turns as soon as I switch to the run position. I bypassed the kds box like I found on the internet because I thought the box was the problem. But it didn't help, the problem still exists.

As soon as I switch to the run position, the starter turns, the brake light lights up and the transmission light lights up and the instruments work. Otherwise there will be no power to the entire humvee.

Many greetings, Benny

OH BOY... A quick free guess . By chance do you have the SRS "STOP-RUN-START' switch wired wrong. You are using this switch ? Here's a picture to help. Note switch ribs on molded parts and maybe label B 4 BATTERY.....R 4 RUN..... S 4 START. 11 A lead should have ribs on it too. Mc Ribs yummy, NOT.



Still does not make sense with the light thing. In and out of the controller box FOR the most part is straight thru for the lighting. Try and not get all twisted around with chasing all the problems at the same time. Let's work the starter (very important IMO)

How about a drawing of what one as jumped or bypassed to get a better picture and pictures, one of the box on the inside could help, not that one will see a gremlin hiding in there LOL. You did pop it open ? Thery are simple at the same time confuse the poop out of some.

Then STOP. Take a step back with thinking cap on and start tracing some wires with go-no voltage checks. Plot them out on the drawing or store them in the human memory bank.

Something stinks and is a misssssss and I am stuck for more info. How much for a ticket to Germany, CAMO

 

[BennyM1097A2]

OH BOY... A quick free guess . By chance do you have the SRS "STOP-RUN-START' switch wired wrong. You are using this switch ? Here's a picture to help. Note switch ribs on molded parts and maybe label B 4 BATTERY.....R 4 RUN..... S 4 START. 11 A lead should have ribs on it too. Mc Ribs yummy, NOT.

View attachment 912245

Still does not make sense with the light thing. In and out of the controller box FOR the most part is straight thru for the lighting. Try and not get all twisted around with chasing all the problems at the same time. Let's work the starter (very important IMO)

How about a drawing of what one as jumped or bypassed to get a better picture and pictures, one of the box on the inside could help, not that one will see a gremlin hiding in there LOL. You did pop it open ? Thery are simple at the same time confuse the poop out of some.

Then STOP. Take a step back with thinking cap on and start tracing some wires with go-no voltage checks. Plot them out on the drawing or store them in the human memory bank.

Something stinks and is a misssssss and I am stuck for more info. How much for a ticket to Germany, CAMO

hello camo. I don't think it's the box. the problem came overnight. In the evening I let the humvee run for about 30 minutes. The next day in the morning I wanted to run it again, then the problem suddenly appeared. srs is connected correctly and in order, light switch is also in order. only then did I bypass the box. but it didn't help either.

What's also strange....I measured a continuity from the "run" cable to the "start 74a" cable with a multimeter.

I'm trying to add a photo of the box

Greetings Benny