M1078 electrical issue

[timberrrrrr]

Howdy folks

New member to the forum. Been reading and learning lots from you guys over the past 6 months.

Recently purchased a 1995 M1078 at auction.

Beautiful truck, super clean but it has an electrical issue. When you flip the switch to turn on the electrical to the dash and start the engine, the dash lights come on, the transmission keypad lights up and the engine will start. Then the transmission keypad will lose power and if I turn the engine off the ignition button has no power to fire it back up again.

I was able to drive the truck for a half hour when first purchased a month or two ago without losing power to the transmission keypad and ignition button. Since then it loses power shortly after flipping the green switch on the dash.

If you wait an hour or two (or some random amount of time I haven't figured out yet) and flip the switch again it will power up the transmission keypad and the button for ignition briefly then typically will lose power within seconds.

All the batteries are brand new. The fuses seem good, but I am going to replace the fuses for the dash lights and starting after I find some at the auto parts store tomorrow.

Seems like there is a bad ground. I pulled the screws holding the dash panel and looked for loose wires or grounds. It all looks like new back there. There is a ground wire attached to the transmission control unit box, it seems to be attached good and tight.

I also looked behind the fuse panel for any loose wires, but it all looks good.

Any thoughts?

 

[Aernan]

In the fuse box there are three screw terminals on left side that should be live with the master switch on. From there near the spare tire is an anti reverse power boxbox. Then to the batteries. Next fault back test from there.

Sent from my SAMSUNG-SM-G930A using Tapatalk

 

[NDT]

If the trans controller is not powered, cranking is inhibited. I would send the controller to transmissioninstruments.com for evaluation and repair if needed. Check the connectors on the unit for looseness when you pull it.

 

[snowtrac nome]

before doing that I would look at the little relay box behind the panel on the passenger side foot well I forgot the name of it but it powers the tcm.

 

[timberrrrrr]

Thank you all for your replies.

I pulled the plugs from behind the ECU and tested that there is power. there is.

I called Transmission instruments and spoke with John. He stated this is a common issue with these controllers.

I pulled the ECU out and am about to box it up and send it to him for repair.

Thank you for your help

 

[wheelspinner]

Thank you all for your replies.

I pulled the plugs from behind the ECU and tested that there is power. there is.

I called Transmission instruments and spoke with John. He stated this is a common issue with these controllers.

I pulled the ECU out and am about to box it up and send it to him for repair.

Thank you for your help

Just before you do that, plug it all back in and check again. I had a truck with an unlocked and loose connector to the back of the keypad with exact same symptoms.