Elusive Electrical Gremlin

[Coonass77]

I'm not sure I can help with the wisdom or hmmwv expert thing, but intermittent electrical stuff is often caused by a poor connection. If you have not already done so, it's probably worth going through all the ground points and also the major positive connections at the bus bar, starter, generator, etc.

When I got my truck a couple months ago, I had an intermittent issue with the wait light blinking instead of staying on. It would happen maybe 1 out of 5 tries. I thought maybe it was battery voltage or unbalanced batteries. Maybe a problem with the start box. I checked all my glow plugs and they were good. My truck was overhauled in 2009 and had no usage since then, so I figured all the electrical connections should be good since there is no corrosion and everything looked new. I ended up going through all the ground locations and found some issues. The main negative cable going from the battery box to the back of the block was loose at the connection point under the truck. They also didn't do a good job of cleaning off the paint at the gound points on the back of the motor (both locations). Finally, one of the crimps/lugs on my battery cables was terrible and loose and some of the negative connections inside the battery box were also sloppy. I spent several hours disassembling, cleaning/polishing, and greasing every "non-plug" connection I could find. I have not seen the blinking wait light since. Even if it doesn't solve the problem you are seeing, it's probably worth the time to make sure all connections are solid. I considered doing the aftermarket ground harness that some folks seem to swear by, but I honestly didn't understand the point of it when it was primarily duplicating the factory grounds. If your factory grounds are good, I don't see the point of the harness and there are a couple situations where I think it could be a safety hazard.

I 100% agree. I could be wrong, but my money is on a loose power or ground connection somewhere. I've seen it more times than I can count over the years.

 

[Mullaney]

I'm not sure I can help with the wisdom or hmmwv expert thing, but intermittent electrical stuff is often caused by a poor connection. If you have not already done so, it's probably worth going through all the ground points and also the major positive connections at the bus bar, starter, generator, etc.

When I got my truck a couple months ago, I had an intermittent issue with the wait light blinking instead of staying on. It would happen maybe 1 out of 5 tries. I thought maybe it was battery voltage or unbalanced batteries. Maybe a problem with the start box. I checked all my glow plugs and they were good. My truck was overhauled in 2009 and had no usage since then, so I figured all the electrical connections should be good since there is no corrosion and everything looked new. I ended up going through all the ground locations and found some issues. The main negative cable going from the battery box to the back of the block was loose at the connection point under the truck. They also didn't do a good job of cleaning off the paint at the gound points on the back of the motor (both locations). Finally, one of the crimps/lugs on my battery cables was terrible and loose and some of the negative connections inside the battery box were also sloppy. I spent several hours disassembling, cleaning/polishing, and greasing every "non-plug" connection I could find. I have not seen the blinking wait light since. Even if it doesn't solve the problem you are seeing, it's probably worth the time to make sure all connections are solid. I considered doing the aftermarket ground harness that some folks seem to swear by, but I honestly didn't understand the point of it when it was primarily duplicating the factory grounds. If your factory grounds are good, I don't see the point of the harness and there are a couple situations where I think it could be a safety hazard.

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@blutow ,

I don't think better and clearer instructions on how a HMMWV electrical system works have been posted. Okay, so it is a lot like what @Milcommoguy explained to me about grounding (I learned a lot in that discussion.).

I think you are on the right track too.

@diesel_dave , this part of working on vehicles sucks. Pure plain and simple it is grunt work at best and if it isn't done thoroughly it just wastes your time. Maybe take a Saturday morning and remove and clean every connection you can easily reach. Maybe work until lunchtime and see if you discover anything loose or corroded?

 

[blutow]

I don't think better and clearer instructions on how a HMMWV electrical system works have been posted. Okay, so it is a lot like what @Milcommoguy explained to me about grounding (I learned a lot in that discussion.).

I think you are on the right track too.

Thanks. While I'm far from an expert on this hmmwv stuff, I know enough about electrical systems to be pretty dangerous. Pic below is the system I built for my camper van. The 4 boxes on the right are custom DIY lithium batteries that can power a rooftop AC for multiple nights. I'm trying to figure out something interesting to do in the hmmwv with the crazy 4000+w generator, but it will probably just be wasted capability. If someone was looking to build an overland camper, a hmmwv with an ambulance body or shelter would be a great starting point. Instead, people are spending stupid $ trying to turn sprinter vans into off-road vehicles (a futile exercise).

 

[Mullaney]

Thanks. While I'm far from an expert on this hmmwv stuff, I know enough about electrical systems to be pretty dangerous. Pic below is the system I built for my camper van. The 4 boxes on the right are custom DIY lithium batteries that can power a rooftop AC for multiple nights. I'm trying to figure out something interesting to do in the hmmwv with the crazy 4000+w generator, but it will probably just be wasted capability. If someone was looking to build an overland camper, a hmmwv with an ambulance body or shelter would be a great starting point. Instead, people are spending stupid $ trying to turn sprinter vans into off-road vehicles (a futile exercise).

View attachment 865265

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That is a NICE looking electrical board!

I have looked at the idea of adding solar panels just to the top of the cab on a couple of M108x trucks, but I have no box on the back. One is a tractor and the other is a wrecker - so it would be an electrical exercise more than having a need to power anything useful.

 

[diesel_dave]

I doubt the reduced engine load is from the alternator not charging. It is still spinning. The reduced load is probably from the a/c clutch disengaging.

It happens when the A/C isn't running even or if Heat is selected instead. You can also hear the engine pitch change slightly when the alternator starts charging again (volt meter returns to green range). It's the same sound change as when the glow plugs are cycling right after a cold start so I'm pretty sure it's the alternator and not something like the A/C compressor which has its own different noise.

 

[Retiredwarhorses]

Tachometer is fed from the generator ,not the PCB…sounds like a failing regulator.

 

[diesel_dave]

Tachometer is fed from the generator ,not the PCB…sounds like a failing regulator.

Does the tach need IGN signal from the PCB to function though? These issues are somehow all related because they happen at the same time and recover at the same time. The PCB seems to be the only common point that I can fathom.

 

[Retiredwarhorses]

Does the tach need IGN signal from the PCB to function though? These issues are somehow all related because they happen at the same time and recover at the same time. The PCB seems to be the only common point that I can fathom.

Take your pick…just imparting my .25 cents.

 

[diesel_dave]

Take your pick…just imparting my .25 cents.

Haha I think your 25 cents is probably worth more than a quarter. I'm just trying to understand how the regulator dying turns off the blower fan when battery voltage is still present. Of course I've driven several times the last few days and it won't act up now. It's waiting until the worst time I'm sure.

 

[Mullaney]

Haha I think your 25 cents is probably worth more than a quarter. I'm just trying to understand how the regulator dying turns off the blower fan when battery voltage is still present. Of course I've driven several times the last few days and it won't act up now. It's waiting until the worst time I'm sure.

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Let's see... In the dark. On the side of a busy highway, In the Rain, with a Heavy Wind - without a flashlight. Yep. That seems to be how it is. Or in the middle of a 95 degree day with no rain for weeks and about ninety percent humidity.

 

[diesel_dave]

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Let's see... In the dark. On the side of a busy highway, In the Rain, with a Heavy Wind - without a flashlight. Yep. That seems to be how it is. Or in the middle of a 95 degree day with no rain for weeks and about ninety percent humidity.

That is EXACTLY what will end up happening. I've been there done that one too many other times with other vehicles.

 

[diesel_dave]

Just an update: The thing has happened a few more times and once right at startup in my driveway which allowed me to dig deeper. Turns out there is no voltage at the IGN input at the regulator when it's doing this. Or rather, not enough voltage? My meter showed 1-2 volts slowly climbing .1 volt every 30 seconds or so. When I try to turn on the AC blower, that drops to zero and stays there. I shook every wire I could get to and no change whatsoever. Finally I just punched the PCB case a few times and voila voltage shot up to 28 volts instantly and the tach/blower kicked on. Been working ever since. No idea what's going on...

 

[Milcommoguy]

Just an update: The thing has happened a few more times and once right at startup in my driveway which allowed me to dig deeper. Turns out there is no voltage at the IGN input at the regulator when it's doing this. Or rather, not enough voltage? My meter showed 1-2 volts slowly climbing .1 volt every 30 seconds or so. When I try to turn on the AC blower, that drops to zero and stays there. I shook every wire I could get to and no change whatsoever. Finally I just punched the PCB case a few times and voila voltage shot up to 28 volts instantly and the tach/blower kicked on. Been working ever since. No idea what's going on...

Intermittent primary power distribution solenoid or relays ...depending on manufacture.

Keep a mallet handy or a Camoteksystems controller handy, CAMO

 

[diesel_dave]

Intermittent primary power distribution solenoid or relays ...depending on manufacture.

Keep a mallet handy or a Camoteksystems controller handy, CAMO

I do believe you are correct. Maybe corroded relay contacts or something. Every day it's looking more and more like I'll be buying your box so I can stop screwing with this dang thing.

 

[kzeyus]

I'm having a very similar issue with an 86 m998 and red dot air.
The red dot gets it's blower power from Heater blower switch and the heater fan suffers from same problem. It happens very seldom. When it does, the generator quits putting out power till a restart, which I think is a function of the regulator seeing a short or some other fault.
Yesterday on a long trip it happened twice, but only after the AC had been running for hours, then shut off for a stop for 30 min or so, then when turning back on AC after starting truck it blows for a second then quits, volt gauge drops to battery level, heater fan won't run. Drive down the road for 30 min or so, I'll see the volts from gen come back up, and fans will work again. Didn't have the problem again till next stopped for a while hours later.
I was thinking at first the high pressure switch was triggering after shutting off AC and reset after cooling while driving some, but now I'm afraid it's related to control box, as wait light acted funny afterwards.

 

[diesel_dave]

I'm having a very similar issue with an 86 m998 and red dot air.
The red dot gets it's blower power from Heater blower switch and the heater fan suffers from same problem. It happens very seldom. When it does, the generator quits putting out power till a restart, which I think is a function of the regulator seeing a short or some other fault.
Yesterday on a long trip it happened twice, but only after the AC had been running for hours, then shut off for a stop for 30 min or so, then when turning back on AC after starting truck it blows for a second then quits, volt gauge drops to battery level, heater fan won't run. Drive down the road for 30 min or so, I'll see the volts from gen come back up, and fans will work again. Didn't have the problem again till next stopped for a while hours later.
I was thinking at first the high pressure switch was triggering after shutting off AC and reset after cooling while driving some, but now I'm afraid it's related to control box, as wait light acted funny afterwards.

This sounds extremely similar to my truck. Next time it does it, give the PCB a few taps and see if that does anything. Would at least narrow it down to some weird PCB issue. As soon as I smacked mine, it started working and it hasn't happened again but I'll see if I can duplicate it when it does.

 

[TOBASH]

This sounds extremely similar to my truck. Next time it does it, give the PCB a few taps and see if that does anything. Would at least narrow it down to some weird PCB issue. As soon as I smacked mine, it started working and it hasn't happened again but I'll see if I can duplicate it when it does.

When you hit a dysfunctional PCB and it starts to work it means a solenoid is going bad. Look up my thread where I collaborated with others on how to build a DIY PCB or PM me if you wanna buy one.

Post number 51

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

good to know, I have fixed my location... Then why is your IP resolving to a different state?

www.steelsoldiers.com

 

[diesel_dave]

When you hit a dysfunctional PCB and it starts to work it means a solenoid is going bad. Look up my thread where I collaborated with others on how to build a DIY PCB or PM me if you wanna buy one.

Post number 51

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

good to know, I have fixed my location... Then why is your IP resolving to a different state?

www.steelsoldiers.com

If it's a relay causing all the issues, I'll definitely open it up and take a look. Should be easy enough to swap out for a new relay.

 

[Milcommoguy]

If it's a relay causing all the issues, I'll definitely open it up and take a look. Should be easy enough to swap out for a new relay.

When one get tired of banging on the controller and not a simple fix...couple that to not fond of a computer / timer taking over your HMMWV experience... here's a proven, off the shelf, no hack, option right here on this post.

Grap an adult beverage and watch the original "CAMOBOX" in action.

Here's the inside of a customers controller. States trouble starting. Had the truck for a while and never started right. Only 11 K miles, Looks brand new. Went to check on the controller box and sent this to us. True story.



Camo at "Camoteksystems.com" For the serious call 661-212-0077.

 

[HoveringHMMWV]

DD,
Did you ever find a solution to this a/c blower problem? I took my M1151A1 out for a test drive yesterday and my rear evaporator blower kept cycling on/off every few minutes.