Need electrical help with an M998 in NY!

[Paincompliance]

Need electrical assistance with an M998 in NY!

I own a 1991 HMMWV with 29k. It runs well but I have an annoying electrical issue. I have NO turn signals, brake lights, or parking lights on the STOP LIGHT setting. On the SER. DRIVE setting I have headlights in high beam only and running lights. Still no turn or brake. There is what looks like an aftermarket alternator on a custom bracket that appears (according to the dash gauge) to be pushing over 12v yet the batteries are in series at 24v. I need help and I'm not afraid to ask. I have a M35A2 but this is my first M998. Does anyone know anybody in NYS (Hudson Valley) that knows this truck? I'm always interested in making new friends!!!

 

[98G]

"HELP!" is usually reserved for situations involving vehicles dead on the side of the road...

 

[Lust4GreenSteel]

Welcome to the group. I know nothing about your truck, but there are many here that can give you guidance.

As 98G requested, you should edit your post to drop the word help from your thread title/heading. I am sure assistance will be forthcoming.

 

[NDT]

Sounds like the 3 lever switch is defective. That is assuming your wiring is not hacked up. On the headlights, verify if the bulbs are good before other diagnostics.

 

[98G]

"Aftermarket" '"custom" and "12v", when referring to a 24V military vehicle all send up red flags for me.

Based on this description, my best guess says someone has "improved" it beyond the point of function...

 

[someoldmoose]

98G, I would tend to agree. Then when the improving didn't work, they gave up and sold it without putting it back where it was. Paincompliance, I suspect you are going to find out if your user name really fits ya. Start with the basics. 24v circuits eat 12v equipment. Have a competent starter / alternator shop (not AutoZone or the like) test your alternator. Tell them EXACTLY what it is to be used on. I suspect it is incorrect for the application but have it verified. After that, charge the batteries with a charger, pull up the TMs for the vehicle and go to town. Basics, basics, basics. NDT nailed it. Check the bulbs (loads), then the switch, and then the wiring. Fix simple things first.

Do the hazard ( 4 way ) flashers work ? Brake and turn lights are over-ridden by the hazard switch. GM vehicles are notorious for this. Operate the hazard light switch a few times making sure it's as "off " as it can be and then see if you have brake and turn signals. If not, grab a voltmeter and a wiring diagram and start probing (carefully). I like to print a copy of the diagram for the circuits I wanna check, and mark on the paper which wires have been checked, which are needing further diagnosis, and which ones were put there by the "enemy" just to mess with me.

Use the resources available. You have an M35 so I hope you have already read all the material on this and other sites relating to it's systems. Same thing for the 998. Read, comprehend, use. If in doubt, ask (which you already have). I love this site and it's members more with every passing day. Party on !

 

[TOBASH]

Start from the beginning.

Verify the output of your alternator and verify the voltage requirement of the starter.

That will answer questions right there.

In the old days, there were systems that allowed a 12V charger to charge batteries BUT would switch the starter circuit system to 24 Volts when cranking the starter. Did some maniac install one of those?

There are 24V Delco starters that I've heard of as a frequent swap to HMMWV's. They require custom modifications to the alternator installation brackets. Is that what you have?

You need to identify what you have prior to trying to figure out a fix.

ALSO:

 

[Presale]

Literally hundreds of possibilities. The TMs are the best for troubleshooting.
Start simple,
Very switch
Verify bulbs
Verify connections
Verify EESS, yes it can affect lights.
With the high beams on does your voltage gauge jump around. EESS may not be cycling glow plug circuit properly and it will cause bulbs to burn out rapidly.

 

[Paincompliance]

Wow, you guys are great! I've been messing with it when I have time after work every night. It's been fun so far. I have a new turn switch and flasher box laying around. I've noticed when the parking lights are on they seem to be pulsing. I have a day off on Wednesday so I'll try a lot more. I truly appreciate you all taking the time to try to help and I'll definitely take the advice and assistance!

 

[Presale]

The pulsing is the EESS going through the glow plug cycle. If it doesn't stop after about 30 seconds it may have a bad regulator circuit inside the EESS. Look under the dash at the EESS box and determine the manufacturer by the affixed label. Pray that's not it they run about $550.

The TM has great troubleshooting diagrams. I had the same problem. The first step is to remove the ground cable from the batteries and then disconnect both plugs on the EESS (one under the dash and one under the hood).

But get this. When I disconnected the ground cable I decided to wait and reconnected it.
Bingo, it must have reset the regulator on the EESS PCB because all my functions started working.

Good luck.

 

[Paincompliance]

I will try that tomorrow night. That would be great if it was something simple. I started noticing the pulse the first time I tried the lights at night a few days ago. It's faint but noticeable.

 

[wheelspinner]

The pulsing is the EESS going through the glow plug cycle. If it doesn't stop after about 30 seconds it may have a bad regulator circuit inside the EESS. Look under the dash at the EESS box and determine the manufacturer by the affixed label. Pray that's not it they run about $550.

The TM has great troubleshooting diagrams. I had the same problem. The first step is to remove the ground cable from the batteries and then disconnect both plugs on the EESS (one under the dash and one under the hood).

But get this. When I disconnected the ground cable I decided to wait and reconnected it.
Bingo, it must have reset the regulator on the EESS PCB because all my functions started working.

Good luck.

its like ctl+alt+del but for HMMWVs