New M998 Ignition problems/batteries/lights

[rbrt43]

I apologize if these questions have already been posted somewhere, but I just joined the forum and haven't been able to find what I am looking for.

I have recently acquired a 1986 M998 cargo/troop carrier. The ignition had been switched from the military lever switch to a keyed switch operation, but I believe the keyed switch may not be properly wired. When I went to pick it up, the local National Guard came out and jumped it off with no problem, but after driving it for 6 hours, when I turn the key absolutely nothing happens. The lights have the pushbutton configuration instead of the lever switches. With the key in the on position, the light control panel does not function at all, however, when I turn the key off, the light control back lights come on. I still cannot get any of the lights to come on, but I am not sure if it is a battery problem or a problem with the way the key switch is wired.

I have the technical manual for the vehicle, but have been unable to find what I am looking for in the 1000+ pages.


Thanks,

 

[tage]

Replace everything back to stock and go from there.

 

[Wire Fox]

You need to be in TM 9-2320-280-20 Vol 2, Chapter 4, Section 7, Rotary Switch Replacement. (Starts on page 4-14, which is the 240th page in my PDF copy). I suspect it won't actually be too helpful, since the wire lead numbers should just match to the numbers on the switch, which likely won't be printed/tagged on an aftermarket switch.

Does the wait light at least briefly come on when you switch from STOP to RUN, and does the starter try to crank when you advance to START? If all of that functions just as described, it's really not going to be your rotary switch that's the problem.

 

[rbrt43]

The manual that I have is TM 9-2380-280-24P-2 Volume 2.

When I turn the key, nothing happens, but when the National Guard jumped it off, they hooked up their cable that plugs in to the connector in the passenger footwell and it jumped almost immediately. Once they jumped it, we never killed it for the next 8 hours and a 300 mile road trip. I had read where someone had posted that size 31 batteries would fit the battery box perfectly and I had picked up a couple of batteries just in case, but when I looked at it before we left with it, it didn't look to me like they would fit.

When I turn the key, absolutely nothing happens. The run light doesn't light up, and the starter does not crank.

 

[NDT]

If the Guard slaved it that means the batteries might be no good. Have them tested and report back.

 

[Wire Fox]

Yup, sounds like batteries. Get them tested prior to spending cash. Still prior to spending cash, try individually charging them overnight on a good charger to try and see if you can salvage the batteries.

Also, the manual ending in 24P is a parts manual. Use it in conjunction with the manual ending in 20 for most maintenance and diagnostic procedures. The manual ending in 34 offers another level of maintenance that may also be helpful for some tasks. Lastly (or really, first) grab a copy of the manual ending in 10 and read it from cover to cover. It is the operating manual, which includes everything from what fluids to use, how much, and how often, plus how to do preventative maintenance and safety checks, to how to use the HMMWV with finesse in normal and abnormal situations. All of these manuals are free downloads on this website. You can click the "Technical Manuals" button at the top of every page and navigate through the page to narrow down to the HMMWV.

 

[rbrt43]

I have downloaded the manuals, 1, 2, and 3, that deal with the maintenance. I will also get 10 and 34. I checked the keyed switch and found it is a 4 contact switch and wonder if that might be the issue, since the rotary switch was only 3 contact. I realize the batteries may be just bad, but that doesn't explain why the light control doesn't work when the key is turned on, and the engine is running. Obviously the alternator works or I wouldn't have been able to drive it 300 miles.

I appreciate all the help I have gotten so for.

Thanks.

 

[Stonewall]

It is a diesel engine. You do not need the alternator in order for the engine to continue running.

I have downloaded the manuals, 1, 2, and 3, that deal with the maintenance. I will also get 10 and 34. I checked the keyed switch and found it is a 4 contact switch and wonder if that might be the issue, since the rotary switch was only 3 contact. I realize the batteries may be just bad, but that doesn't explain why the light control doesn't work when the key is turned on, and the engine is running. Obviously the alternator works or I wouldn't have been able to drive it 300 miles.

I appreciate all the help I have gotten so for.

Thanks.

 

[NDT]

The light switch is not wired through the ignition switch. The pushbotton light switches have a very high failure rate. If the keyed ignition was working ok for the Guard, they way it is wired is not you issue, although it may have failed.

Stonewall don't forget the injector pump solenoid, instruments, and fan solenoid are a constant several amp draw on the batteries if the alternator is bad.

 

[rbrt43]

I had the batteries tested yesterday. Both tested bad. 0 CCA on both. I will be replacing them next week. I know there are several threads dealing with batteries and various sizes, but am I correct that any pair of 12 volt batteries that have at least 900 CCA's should work? I will just need to shim around them.

Thanks,

 

[riderdan]

Yes. When I got my truck it had two of the cheapest possible wally world batteries in it, and it started fine. Of course, one of them died soon thereafter. The funny thing is, they were less than a year old, so I got a replacement for free. At some point, I'll have to put a pair of "real" batteries in there, but it's working fine for the moment.

 

[TOBASH]

Start simple.

I will again state that when I first received my vehicle it would not start. It was because the transmission selector was not in Neutral.

Start from the battery leads and battery charge. Make sure every lead is properly attached without corrosion. Work from there.

Many of us have keyed ignition as a theft retarding system. Might not be the issue.

Have you tried calling the guys who sold you the vehicle to see if they have tips and tricks? They know this HMMWV best.

T

 

[NormB]

I had the batteries tested yesterday. Both tested bad. 0 CCA on both. I will be replacing them next week. I know there are several threads dealing with batteries and various sizes, but am I correct that any pair of 12 volt batteries that have at least 900 CCA's should work? I will just need to shim around them. Thanks,

Last I heard military has been going with OPTIMA yellow tops - size D34, - and you CAN find the plastic adapters to fit the tray for the 6TLs (6LT? Whatever, the big square ones), just be careful with the clamp and avoid shorting out terminals (you'll see). That's about 1600 CCAs, IIRC. Works for me.

I got a pair through Amazon last fall for about $300, delivered. Don't know if they're still selling 'em.

 

[Wire Fox]

Last I heard military has been going with OPTIMA yellow tops - size D34, - and you CAN find the plastic adapters to fit the tray for the 6TLs (6LT? Whatever, the big square ones), just be careful with the clamp and avoid shorting out terminals (you'll see). That's about 1600 CCAs, IIRC. Works for me.

I got a pair through Amazon last fall for about $300, delivered. Don't know if they're still selling 'em.

There's a notice in one of the PS Mags I read recently reminding units that Optima batteries are not authorized for use in any combat vehicle, but was ok for use in generators and other support equipment. That might be some CYA stuff, because I'm certainly tempted to do so myself...

 

[rbrt43]

When I checked I noticed that the Yellow top optima D34 battery is a deep cycle battery. Is there a distinct advantage with deep cycle batteries over regular batteries in the M998?

 

[Bulldogger]

When I checked I noticed that the Yellow top optima D34 battery is a deep cycle battery. Is there a distinct advantage with deep cycle batteries over regular batteries in the M998?

Absolutely not! The standard military issue battery is a deep cycle battery.
Bulldogger

 

[NormB]

When I checked I noticed that the Yellow top optima D34 battery is a deep cycle battery. Is there a distinct advantage with deep cycle batteries over regular batteries in the M998?

Not really. I just wanted a sealed unit, and with whatever information I had on hand at the time I was led to these batteries. Red tops would probabaly work just as well.

 

[rbrt43]

Sorry for raging on, but now I am confused. Earlier tonight I removed the old batteries from the HMMWV and used a multi-meter to test voltage on them. I know it's not the best, but it is all that I had. They both tested about 7 volts, but what has me confused is that the 2nd battery (I will call the battery that had the positive connected to the vehicle the 1st battery and the one with the ground connected to the vehicle as the 2nd battery) when I put the positive lead from my multi-meter on the positive post and the negative lead on the negative post showed -7.4V, but when I checked the 1st battery the same way, it showed 7.4V, without the -. On the second battery if I reversed the leads, - to+ and + to- it showed 7.4V. I have never dealt with a 24V system before, but I do remember enough from science that the + of battery 2 must connect to the - of battery 1 in order for it to provide 24V, but I do not understand why battery 2 is showing reversed from the way it should.

I have read some of the other threads about batteries and such and I think I am just going to visit our local NAPA store (have a good relationship with the owner) and get a couple of batteries to try to get it started and running. Further down the line I will get better batteries if these do not work out.

 

[TOBASH]

Sorry for raging on, but now I am confused. Earlier tonight I removed the old batteries from the HMMWV and used a multi-meter to test voltage on them. I know it's not the best, but it is all that I had. They both tested about 7 volts, but what has me confused is that the 2nd battery (I will call the battery that had the positive connected to the vehicle the 1st battery and the one with the ground connected to the vehicle as the 2nd battery) when I put the positive lead from my multi-meter on the positive post and the negative lead on the negative post showed -7.4V, but when I checked the 1st battery the same way, it showed 7.4V, without the -. On the second battery if I reversed the leads, - to+ and + to- it showed 7.4V. I have never dealt with a 24V system before, but I do remember enough from science that the + of battery 2 must connect to the - of battery 1 in order for it to provide 24V, but I do not understand why battery 2 is showing reversed from the way it should.

A battery may reverse polarity under certain abnormal charging and discharging conditions.

You need to check your generator for proper output.

You need to check your system to ensure that when your vehicle is OFF it has no drain on the battery.

Search for another thread about battery changing/flipping polarity. Interesting read from a few months back.

Drain the "backwards battery" to zero, then recharge in correct polarity.

Best,

T

 

[rbrt43]

Well, I put in some new batteries today and it fired right off. I think there are still some electrical issues cause the lights don't work and the charge gauge on the dash just went to yellow, which is better than it did on the trip up here. The batteries do not fit the original trays so I am thinking about removing them, or at a minimum, cutting a piece of wood and put in them with a piece of heavy rubber (truck bed liner) on top of the wood. I think that until I can try to figure out what other electrical issues it has I am going to disconnect the jumper cable between the batteries to make sure they are not drained down before I can trouble shoot the issues, since I don't have any way to charge them, without removing them.