LMTV Smoke Test

[hawk-aggie]

2002 1078A1
Had CTIS issue - replaced pressure switch & CTIS module. while diagnosing that problem, I had 2 used modules and one new one, along with an old and new pressure switch. In trying to eliminate faulty part(s) I tried various combinations of old parts, new & old parts, and just new parts.

First test was using two used CTIS modules and the original pressure switch. In doing so, I had to start and run the truck several times. With each change of parts, I always shut down the engine and turned off the master switch. Had to let the air tanks get full on the first run, so engine ran long enough to do that. On about the third start up, and after running a couple of minutes, smoke started coming out of the passenger side dash. At the same time, the Check Trans, No Charge, ABS, and one other light came on, and both voltmeters went to "0". I shut everything down, turned the master switch off, then disassembled the passenger side dash. I didn't see any evidence of burning/melting, although it was evident something had happened because of the smell. I didn't remove any of the wire loom covering. I reassembled everything, and the truck sat while I was waiting on a new CTIS pressure switch.

Second test was using the two used CTIS modules and a new one, with a new pressure switch. Neither of the used CTIS modules worked properly with the new pressure switch. Installed the new CTIS module. Started engine the third time. Saw a little whiff of smoke coming out of the dash. Again, the Check Trans, No Charge, and one other light came on, and both voltmeters went to "0". I shut everything down, turned the master switch off, then disassembled the passenger side dash. Still no sign of melting or burning on the wire loom. I have not yet removed any wire loom to look at the wires themselves, because I only thought to do that at about 0-dark-30 this morning. I will do that when I circle back around to the LMTV from working on more pressing projects.

I tried to be as detailed as possible. Any thoughts, ideas, or directions would be appreciated. Thanks in advance.

 

[DeMilitarized]

2002 1078A1
Had CTIS issue - replaced pressure switch & CTIS module. while diagnosing that problem, I had 2 used modules and one new one, along with an old and new pressure switch. In trying to eliminate faulty part(s) I tried various combinations of old parts, new & old parts, and just new parts.

First test was using two used CTIS modules and the original pressure switch. In doing so, I had to start and run the truck several times. With each change of parts, I always shut down the engine and turned off the master switch. Had to let the air tanks get full on the first run, so engine ran long enough to do that. On about the third start up, and after running a couple of minutes, smoke started coming out of the passenger side dash. At the same time, the Check Trans, No Charge, ABS, and one other light came on, and both voltmeters went to "0". I shut everything down, turned the master switch off, then disassembled the passenger side dash. I didn't see any evidence of burning/melting, although it was evident something had happened because of the smell. I didn't remove any of the wire loom covering. I reassembled everything, and the truck sat while I was waiting on a new CTIS pressure switch.

Second test was using the two used CTIS modules and a new one, with a new pressure switch. Neither of the used CTIS modules worked properly with the new pressure switch. Installed the new CTIS module. Started engine the third time. Saw a little whiff of smoke coming out of the dash. Again, the Check Trans, No Charge, and one other light came on, and both voltmeters went to "0". I shut everything down, turned the master switch off, then disassembled the passenger side dash. Still no sign of melting or burning on the wire loom. I have not yet removed any wire loom to look at the wires themselves, because I only thought to do that at about 0-dark-30 this morning. I will do that when I circle back around to the LMTV from working on more pressing projects.

I tried to be as detailed as possible. Any thoughts, ideas, or directions would be appreciated. Thanks in advance.

Likely have a shorting wire causing a fault and gets hot. Take all the loom off of the wires and expose as many as possible. Have someone watch closely where the smoke is coming from while you start it up and you should be able to locate the bad wire/ module. If you have a more detailed symptoms of your ctis system and what it does currently may be able to help.

 

[Ronmar]

Short or a very loose/intermittent connection that is cooking off trying to feed its normal current. Read the codes on the trans, you probably have a low voltage fault stored. Then you need to look back along that trans power pathway… most of the connections are plug in or spade terminals, but the main ignition relays under the power panel use screw terminals. I would flip the panel frame over and inspect those first…

first rule on asking a tech question: state the year and model of the truck. From the lights you described I am assuming it is an A1, or is it an A1R?

 

[DeMilitarized]

Short or a very loose/intermittent connection that is cooking off trying to feed its normal current. Read the codes on the trans, you probably have a low voltage fault stored. Then you need to look back along that trans power pathway… most of the connections are plug in or spade terminals, but the main ignition relays under the power panel use screw terminals. I would flip the panel frame over and inspect those first…

first rule on asking a tech question: state the year and model of the truck. From the lights you described I am assuming it is an A1, or is it an A1R?

Literally at the top of the page it is labeled 2002 m1078a1

 

[Ronmar]

Literally at the top of the page it is labeled 2002 m1078a1

Wow! So used to NOT seeing it I scanned right past it, feels like its going to be another monday

 

[RRaulston]

2002 1078A1
Had CTIS issue - replaced pressure switch & CTIS module. while diagnosing that problem, I had 2 used modules and one new one, along with an old and new pressure switch. In trying to eliminate faulty part(s) I tried various combinations of old parts, new & old parts, and just new parts.

First test was using two used CTIS modules and the original pressure switch. In doing so, I had to start and run the truck several times. With each change of parts, I always shut down the engine and turned off the master switch. Had to let the air tanks get full on the first run, so engine ran long enough to do that. On about the third start up, and after running a couple of minutes, smoke started coming out of the passenger side dash. At the same time, the Check Trans, No Charge, ABS, and one other light came on, and both voltmeters went to "0". I shut everything down, turned the master switch off, then disassembled the passenger side dash. I didn't see any evidence of burning/melting, although it was evident something had happened because of the smell. I didn't remove any of the wire loom covering. I reassembled everything, and the truck sat while I was waiting on a new CTIS pressure switch.

Second test was using the two used CTIS modules and a new one, with a new pressure switch. Neither of the used CTIS modules worked properly with the new pressure switch. Installed the new CTIS module. Started engine the third time. Saw a little whiff of smoke coming out of the dash. Again, the Check Trans, No Charge, and one other light came on, and both voltmeters went to "0". I shut everything down, turned the master switch off, then disassembled the passenger side dash. Still no sign of melting or burning on the wire loom. I have not yet removed any wire loom to look at the wires themselves, because I only thought to do that at about 0-dark-30 this morning. I will do that when I circle back around to the LMTV from working on more pressing projects.

I tried to be as detailed as possible. Any thoughts, ideas, or directions would be appreciated. Thanks in advance.

In response to your CTIS issue, mine didn't work either and I suspected the pressure switch was bad as well. I plumbed a pressure gauge into the wet tank and discovered I was only building 110psi even though my dash gauge was pegged out. Ronmar educated me on adjusting the compressor governor and I cranked it up to 125psi in the wet tank. That activated the pressure switch and it all started working. So before throwing the parts cannon at it, do you even meet the minimum operating pressure?? Just a thought...

 

[hawk-aggie]

In response to your CTIS issue, mine didn't work either and I suspected the pressure switch was bad as well. I plumbed a pressure gauge into the wet tank and discovered I was only building 110psi even though my dash gauge was pegged out. Ronmar educated me on adjusting the compressor governor and I cranked it up to 125psi in the wet tank. That activated the pressure switch and it all started working. So before throwing the parts cannon at it, do you even meet the minimum operating pressure?? Just a thought...

All that CTIS info was background to let you guys know what I was doing at the time. The CTIS is working now. The point of the posting was in relation to the smoke coming from the dash.

 

[Skyhawk13205]

Do you have the bussman PDP modules or the circuit board PDP. I smoked my PDP by reverse current my relays shorting the fly back diodes. The diodes become an alternate electrical path over currenting the traces burning the potting off then eventually destroying the trace.