Fmtv transmission and CTIS displays suddenly turned off

[Keith Knight]

Here’s the scenario, 2003 M1078A1 I’m driving down the beach at the north end of the outer banks NC where they have wild horses roaming around. I turned the CTIS on it come on normal, select XC it aired down as expected. About 1 mile into it I decided to air down to the sand settling again it airs down as expected. Everything is working great I even set the cruise control at about 22mph. About 4 miles into the beach excursion the sand got a little soft and everything started working a little harder and for some reason it kicked the cruise control off! That’s weird and I couldn’t set the cruise again until I actually hit the cruise off switch and back on then I set the cruise again at the same speed with no problem. At about 8 miles in the beach is coming to an end “Virginia state line” and the distance between the dunes and the waves are getting very narrow. And I need to do a U turn so I decided to shift the transmission into off road mode and noticed the display on the shift selector is blank!!! I stopped put it reverse and it goes into reverse put it in neutral and it shifts to neutral put it back in drive and proceed forward and it feels like it in off road mode. But the display is still blank even the round led indicator is not working. Then I noticed the CTIS doesn’t have any leds illuminated. I powered the CTIS off and on a few times and as soon as I turned it on all leds would illuminate for a brief second then off. Not knowing what was going on I did the U turn and went back south. Everything was shifting normally I could even feel it switch transmission modes. As I got closer to pavement I pressed the highway mode on the CTIS and it sounds like it airing the tires up. So still no displays but everything seems to be working. First chance I got to pull over I stopped left the truck running and checked all the tire pressures and they were all pretty close to the set 85psi. I topped off the couple that were a little low got back in the truck and now all the displays are working properly!!!!
Any clues what caused this and how to prevent it in the future. My only guess is when I was in sand mode I hit the over speed but that should just force it into XC mode I think. I just know it freaked me out and didn’t like that type of situation thinking the transmission was flaking out.

 

[wandering neurons]

DId you accidentally switch your lights to Blackout mode? That would kill those displays for certain, especially the transmission control panel.

Here’s the scenario, 2003 M1078A1 I’m driving down the beach at the north end of the outer banks NC where they have wild horses roaming around. I turned the CTIS on it come on normal, select XC it aired down as expected. About 1 mile into it I decided to air down to the sand settling again it airs down as expected. Everything is working great I even set the cruise control at about 22mph. About 4 miles into the beach excursion the sand got a little soft and everything started working a little harder and for some reason it kicked the cruise control off! That’s weird and I couldn’t set the cruise again until I actually hit the cruise off switch and back on then I set the cruise again at the same speed with no problem. At about 8 miles in the beach is coming to an end “Virginia state line” and the distance between the dunes and the waves are getting very narrow. And I need to do a U turn so I decided to shift the transmission into off road mode and noticed the display on the shift selector is blank!!! I stopped put it reverse and it goes into reverse put it in neutral and it shifts to neutral put it back in drive and proceed forward and it feels like it in off road mode. But the display is still blank even the round led indicator is not working. Then I noticed the CTIS doesn’t have any leds illuminated. I powered the CTIS off and on a few times and as soon as I turned it on all leds would illuminate for a brief second then off. Not knowing what was going on I did the U turn and went back south. Everything was shifting normally I could even feel it switch transmission modes. As I got closer to pavement I pressed the highway mode on the CTIS and it sounds like it airing the tires up. So still no displays but everything seems to be working. First chance I got to pull over I stopped left the truck running and checked all the tire pressures and they were all pretty close to the set 85psi. I topped off the couple that were a little low got back in the truck and now all the displays are working properly!!!!
Any clues what caused this and how to prevent it in the future. My only guess is when I was in sand mode I hit the over speed but that should just force it into XC mode I think. I just know it freaked me out and didn’t like that type of situation thinking the transmission was flaking out.

 

[Keith Knight]

Nope, I have the newer style that has the push buttons. Extremely difficult to just turn the stop lights on or service lights. And it just fixed itself while I was out checking tire pressure.

 

[Ronmar]

Since everything was still working, it does sound like the dimmer/blackout circuit went wonky…

 

[Ronmar]

I cannot remember if it applies or removes power to dim the display. On the A1 K29(blackout relay)controls this using the de-energized contacts. CB66 provides power from the light sw to energize the relay. So with things turned on and the trans and CTIS visible, what happens to those displays when you pull CB66 or K29?

 

[Keith Knight]

I’ll check that and I’ll also turn black out on. But in black out mode shouldn’t things illuminated in RED stay on?

 

[ramdough]

Since everything was still working, it does sound like the dimmer/blackout circuit went wonky…

That was my guess.

The switch has circuitry in it. Maybe it is burned out. My truck came with your style switch and was swapped to manual due to a failure.


Sent from my iPhone using Tapatalk

 

[Suprman]

I prefer the old style light switch. One less gizmo to give me trouble

 

[Keith Knight]

So I just tested that theory and selecting each different Black out option nothing turned the shift indicator/display off. Which that’s why it’s Red so it doesn’t bother night vision.

 

[Ronmar]

So I just tested that theory and selecting each different Black out option nothing turned the shift indicator/display off. Which that’s why it’s Red so it doesn’t bother night vision.

It should still blackout. Its not as much about night vision as it is about light discipline(You look at that display with NVGs on and they will probably bloom out)

I think I got my brain around how the circuit is supposed to work. When you select blackout on the light controller it sends 12v to CB66 this power passes thru 66 and right back out to the vehicle blackout lights, the trans controller(blackout request) and energizes K29.

CTIS light control is assbackwards, and it is 24v. The LED power is provided externally and when it is removed, the lights go out. it gets its 24V power from CB41 via the de-energized contacts of K29. When you select blackout, the truck BO lights come on, and the trans goes dark. This also energizes K29 shifting the CB41 power from CTIS to the trailer/intervehicular 24v BO lighting output plugs at the back.

So I suspect your switch un-commanded, decided to deliver the BO output to CB66. You can also check for proper BO control operation. When you select BO, K29 should energize. You should also see 12V on CB66. If this doesn’t work, you can simulate BO from the light switch by applying 12V to CB66’s socket pins. 12v applied to one of the socket ports(try them both) should power K29 and the displays should go dark…

Those pushbutton light switches have more than their fair share of issues…

 

[coachgeo]

....

Those pushbutton light switches have more than their fair share of issues…

@Keith Knight ... does your light switch have a ground wire on it? Updated push button ones do. The non grounded as Ronmar mentions had problems... including a few fires.... traced back to the light switch.

 

[Keith Knight]

I was referring to a persons night vision not night vision goggles.
Where would the ground wire be in the wire loom or a separate ground wire to the switch chassis?
Thanks Ron I’ll get in there and check those things out. When all this rain passes. But you’re confident that those are supposed to turn off with black out? Because mine didn’t when I switched it on which would indicate a bad light switch.

 

[Ronmar]

Well you saw them blackout… The fact they blacked out all by themselves for you indicates to me a bad lights witch…

 

[coachgeo]

...
Where would the ground wire be in the wire loom or a separate ground wire to the switch chassis?

not sure the full story.... seems that the older lever style switch the ground was thru the mounting bolts. On the new push button there was either not a seperate ground bolt until a second generation.... or there was one all along, but soldier/mechanic skipped using it thinking since the lever type did not use one on rig they were upgrading; then the pushbutton would not need to use it either. Then problems started. Eventually they made grounding manidotry.

Pictures here show the ground screw in second pic. It's a photo of back side of switch. View of screw is covered a bit by site's watermark logo. Photo of install manual (last pic) shows the ground cable. It does not go to harness.... just goes to body somewhere on A0's and maybe early A1's. For all I know the ground did eventually end up as part of wiring harness on later A1's??

MILITARY TRUCK LED PUSH BUTTON MASTER LIGHT SWITCH

Upgrade your military truck with our LED push button master light switch. Replacing the old three lever switch, it features illuminated buttons and extra functions.

midwestmilitaryequipment.com

 

[Keith Knight]

Finally had time and opened the fuse panel and dash panel.
The push button light switch does have a separate ground on it.
When I turned the two different BO options on the only thing I could see occurring is the hazard relay LED turned off. None of the BO relays LED’s came on nor did I hear any thing. Power was never sent to CB66.
I banged on the fuse panel and the light switch trying to recreate the problem with no success.
I think I would rather just disable the BO feature. Think by removing all the fuses and relays labeled BO would do the trick or are they needed for other reasons? I’m also going to try getting an older style switch while on the road. I’m going to be going by Superman’s pawn shop in a month or so, he might have one he could sell me.

 

[Ronmar]

The relay I was discussing provides power to ctis when de-energized, so it needs to stay or pull it and jumper pin 30-87A. Pullung CB66 will disable its function though...

 

[Keith Knight]

Thanks Ron, greatly appreciate all you do.

 

[Keith Knight]

After a couple weeks it did it again…..pulled the fuse panel cover off and sure enough the BO relay was on and only the stop light LED was illuminated. I pulled CB66 fuse and the relay turned off and everything was back to normal. I’ll be driving by Superman’s place and pick up an old style light switch next week