CTIS hwy blinks again after 30 seconds

Third From Texas · Nov 9, 2018

Interesting to know that Motorola also made ECUs for LMTV/MTVs.

I'd only seen Dana Spicer ECUs until today.

Plasa · Nov 10, 2018

coachgeo said:
whomever did the interior of both cab and rear habitat did an awesome job. Would love to see more. Curious of your rear bumper too.

I did all the job... Interiour of cab and habitat, external painting of whole truck etc...

Christian

Third From Texas · Nov 10, 2018

Plasa said:
I did all the job... Interiour of cab and habitat, external painting of whole truck etc...

Looks like about the same size box as I'm going with (a 14' ambulance box like Coachgeo is using as well). His truck already has the spare and intake removed, but I plan on leaving it like you did then add a slight cut in the rear to maintain the departure angle.

Love what you did for the console and headliner. Top-notch work there !

Any more pics from the box interior? What is on the forward side of the room?

And as Coach said, show some more of that bumper and how it hinges up.

Plasa · Nov 10, 2018

Hello all.
Today I dig a little bit more. Seems that there are 2 diffrent valves for 2 diffrent pressures:

https://www.oshkoshequipment.com/products/detail/84/1755/CTIS-Wheel-Valve-Kit-Rear-Wheel-90PSI (for 90psi)

https://www.oshkoshequipment.com/products/detail/84/4649/CTIS-Wheel-Air-Valve-70PSI-System (for 70 psi)

I search again for air leaks today but I didn't found anything. The tires are keeping for more than a day the same pressure, even if manual inflated to 90psi. See also the post of stellaevil in the CTIS main thread:

On the m939a2 trucks there was an upgrade for running higher pressure. It was a newer ecu, replacement pressure sensor and wheel valve upgrades to what appears to be the same ones as the lmtv uses. Is there any way to trick the first gen lmtv systems into running higher pressure by just changing the pressure sender? Or putting a small resistor inline with one of the sensor wires so the system thinks the pressure is slightly lower than it really is.
The sensor is a atmospheric or PSIA so normal atmosphere it puts out roughly .573 volts at .039psi/volt. Say 80psi = 3.12v. If you put in a "Resistor Divider" designed to reduce the signal wire voltage by 10% the system will see 80psi tires as 72psi and what it thinks is now 80psi tires would actually be 88psi (roughly). Keep in mind that atmospheric reading is now 10% low and if you live on a mountain the lower reading could cause a Fault. The more important issue is that the wheel valve on the LMTV front left can't close much above 84psi on a warm day. Resistor Divider = 3 resistors configured properly across the signal and ground wires.

Why is the front left different than the other valves? I was thinking I would only have to put a resistor on the positive side not the ground.

The front QRV is mounted on the right side frame rail so there is allot longer tubing to get to the left hub. That extra tubing make it harder for the valve to close at higher tire pressures and it get's worse as the valve diaphragms get's colder. Messing with the transducer supply current may cause problems that's why it should be on the signal wire which is very high resistance. I am not advocating trying this.

Maybe the 90psi valves have harder springs, and the M1078 have only 70 psi wheel valves? For sure you know more than me, so excuse me if I insist in this 70/90 psi diffrence...

Next days I will make some picture or the rear bumper and habitat... So please be patient with me

Christian

m-35tom · Nov 10, 2018

Third From Texas said:
Interesting to know that Motorola also made ECUs for LMTV/MTVs.

I'd only seen Dana Spicer ECUs until today.

My 94 has Motorola symbol on circuit board.

coachgeo · Nov 10, 2018

Plasa said:
Hello all.
Today I dig a little bit more. Seems that there are 2 diffrent valves for 2 diffrent pressures:...

Neither of those are for an FMTV. Both are for M939's and far as I know where not used on any fmtv's. IF either are on your truck then someone frankensteined the ctis. Probably not the case. Did you buy from individual or from Military auction?

BTW..... great to have an FMTV owner from other side of the Ocean participating.

Plasa · Nov 11, 2018

coachgeo said:
Neither of those are for an FMTV. Both are for M939's and far as I know where not used on any fmtv's. IF either are on your truck then someone frankensteined the ctis. Probably not the case. Did you buy from individual or from Military auction?
BTW..... great to have an FMTV owner from other side of the Ocean participating.

I'm proud to be member of this fantastic forum, much better than other forums where the netiquette don't exist...

I bough it from a german seller of military trucks. He also made the frame for habitat and second gas tank. The original ECU have 5 solid ligths (I have it), so he switch from original ECU to the actual ECU. I did a search on internet. The ECU is for a M939 truck, the part# eaton 6ac3500a01 is visible on bottom of the ECU.

I doubt that the M939 ECU will work on a M1078 without other modifications. Maybe someone have more info about.

What I know is that the truck was in North Carolina, after that in 2012 was in Germany till auction.

I will pick up the part number of the wheel valves and make some picture of the bumber and habitat...

Thank you all!

Christian

coachgeo · Nov 11, 2018

Some good reading applies here about what is, isnt good air pressure. Do some additional searches about max psi. Some of it surprised me. Just maybe the German feller who modified things is a pretty smart feller?

https://www.4wheelparts.com/a/tire-wheel-package-guide-tire-pressure-checker

Plasa · Nov 11, 2018

coachgeo said:
Some good reading applies here about what is, isnt good air pressure. Do some additional searches about max psi. Some of it surprised me. Just maybe the German feller who modified things is a pretty smart feller?
https://www.4wheelparts.com/a/tire-wheel-package-guide-tire-pressure-checker

Interesting indeed. I did a unwanted chalk test some days ago, with 90psi. This pressure is definitivly too high, The tires have only in the middle (60-70%) ground contact. 60 psi looks more natural..

Christian

coachgeo · Nov 11, 2018

Plasa said:
Interesting indeed. I did a unwanted chalk test some days ago, with 90psi. This pressure is definitivly too high, The tires have only in the middle (60-70%) ground contact. 60 psi looks more natural..

Christian

but was the setup he put in intended not for now but for AFTER camper box installed? IMHO if all your valves etc. check out as no leaks.... leave it as is and re-evaluate after your camper box is installed and fully loaded. Unless of course your driving her a bunch right now and do not want to wear out your tires.

Plasa · Nov 12, 2018

coachgeo said:
but was the setup he put in intended not for now but for AFTER camper box installed? IMHO if all your valves etc. check out as no leaks.... leave it as is and re-evaluate after your camper box is installed and fully loaded. Unless of course your driving her a bunch right now and do not want to wear out your tires.

No, he change the ECU because the old one did not work. He put the only one that is working, and that is the M939 wrecker ECU...

Christian

Plasa · Jan 12, 2019

Sorry for the delay, but I was taken by the ctis project. Here is a picture of the back bumper..

Christian

coachgeo said:
whomever did the interior of both cab and rear habitat did an awesome job. Would love to see more. Curious of your rear bumper too.

As to MTV CTIS valve causing issues with other components..... have not heard/seen a mention that valves used are any different between the LMTV's and the MTV's. Pretty sure it is all same valves so once you're all repaired in leaks and valves, if it is an MTV controller you should be fine in that respect.

Others with more knowledge will chime and and clarify though.

Plasa · Jan 12, 2019

On front of the box is the kitchen and the bathroom...

Sorry, I am not as good as Seth for pictures and text...

Christian

Third From Texas said:
Looks like about the same size box as I'm going with (a 14' ambulance box like Coachgeo is using as well). His truck already has the spare and intake removed, but I plan on leaving it like you did then add a slight cut in the rear to maintain the departure angle.

Love what you did for the console and headliner. Top-notch work there !

Any more pics from the box interior? What is on the forward side of the room?

And as Coach said, show some more of that bumper and how it hinges up.

Dock Rocker · Jan 13, 2019

Plasa said:
No, he change the ECU because the old one did not work. He put the only one that is working, and that is the M939 wrecker ECU...

Christian

I may have missed it in the thread somewhere but could the issue be that the box from the 939 is not compatible with the LMTV CTIS system?
Should you try to get a known good LMTV box and instal it to see how it acts?

Sent from my iPhone using Tapatalk

coachgeo · Jan 13, 2019

Plasa said:
Sorry for the delay, but I was taken by the ctis project. Here is a picture of the back bumper....[img .... /img]
Christian

Thanks..... next time you swing it up please take a shot of how it clips/pins?? up out of the way

coachgeo · Jan 13, 2019

Dock Rocker said:
I may have missed it in the thread somewhere but could the issue be that the box from the 939 is not compatible with the LMTV CTIS system?
Should you try to get a known good LMTV box and instal it to see how it acts?

Sent from my iPhone using Tapatalk

Yes its not compatable.... from previous postings.... not heard back on where he is on his ctis adventure. Being in Italy he can't just find another known to work one to swap test with that easily.

CTIS hwy blinks again after 30 seconds

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