Dashboard electrical issue, trying to fix it myself - FIXED IT (kinda)

Dempsey7771 · Jan 17, 2019

PermanentTourist said: ↑

Update: success!

I downloaded a very dense and technical manual about the cab electrical system, and learned that:
A: these are called MSF switches on a CAN bus. (Sorry mr. Uncleal, not J1939. That controls the more serious stuff like the engine.)
B: the box with the flasher triangle is the MSF Master. It controls all the other so called slave switch modules by a three wire connector. It has multiple inputs for those connectors.

My particular version of the master controller seemed to have two slave switch connectors going into it: one for the important front switches and one for the rear ones. So I tried pulling out the rear switch connector and voila! All the front switches came back on! The check engine light and the beeping went away, and my engine brake works again.

I guess the signal wire running to the rear switches has a short somewhere, and it was confusing the whole digital system, flooding it with white noise so it couldn't "hear" all the other switches. I will have to track it down eventually, but meanwhile I can keep running! It'll be a bit annoying not being able to control lights from the bunk, but that's a project for some other day, when I'm stuck somewhere waiting for freight and bored.

I am so relieved, I was afraid that I fried something expensive. Now time to put the truck back together and go to sleep.
Click to expand...

What rear switch connector did you pull out Im having the same problem?

Sherm117 · Jan 5, 2020

PermanentTourist said: ↑

2014 Cascadia

Earlier today, the whole row of lower dash swithes from the emergency flasher all the way to the AC controls went out. Backlight is out, and the switches don't do anything. No backup lights, no mirror heat, nothing. The check engine light is on and the display is beeping contnuously and annoyingly and saying "Engine Braking Problem" because it can't read the engine braking strength switch (which is one of the row of switches that went dark) and is getting confused. The check engine code is 973, which is again because it's not sensing the switch. The flasher still works, btw, just not the black switches.

An interesting data point is that in the few minutes that the switches were blinking out, there was a static sound from the left door speaker.

So I've concluded that the problem is with whatever wiring is supplying power to that bank of switches. Is there a fuse that handles them? Might the left speaker wire somehow shorted with the switches' power wire, thus making that noise? Or is it something entirely different.

I know the mechanics will probably charge me a grand for digging in there and changing a $20 part or a $2 wire, so I'm gonna take off the front panel and do some passive investigating. But if anyone has experienced a similar issue or has experience with dash wiring please let me know. A wiring diagram would be great, also. Thanks.

Update: all the switches are out, even the sleeper ones. Gotta be a fuse
Click to expand...

Hey man if you can remember what codes did you have when all of this was happening? Did you get any codes for your Sam cab or sam chasis?

PermanentTourist · Jan 5, 2020

Sherm117 said: ↑

Hey man if you can remember what codes did you have when all of this was happening? Did you get any codes for your Sam cab or sam chasis?
Click to expand...

It was SAM cab, the triangle flasher unit. One of my sleeper buttons is bad, so and it was confusing the whole system, like christmas lights. I disconnected the rear buttons from the triangle flasher computer, and it's been fine ever since. Never did get around to fixing the rear button.

Sherm117 · Jan 5, 2020

PermanentTourist said: ↑

It was SAM cab, the triangle flasher unit. One of my sleeper buttons is bad, so and it was confusing the whole system, like christmas lights. I disconnected the rear buttons from the triangle flasher computer, and it's been fine ever since. Never did get around to fixing the rear button.
Click to expand...

I'm having the same issues, all my codes are going towards the same cab and sam chasis. I replaced the Sam chasis and still have codes for msf loosing connection. Can you tell me which switch was it that you disconnected and where is it located?

PermanentTourist · Jan 5, 2020

Sherm117 said: ↑

I'm having the same issues, all my codes are going towards the same cab and sam chasis. I replaced the Sam chasis and still have codes for msf loosing connection. Can you tell me which switch was it that you disconnected and where is it located?
Click to expand...

It was like three years ago so I don't exactly remember. From what I remember, from the triangle flasher control unit there are connections going to the rear switches, and the two Banks of front switches. I disconnected the one going to the rear switches. I forget which one it is.

Try disconnecting one connection at a time and see if the problem goes away. That way maybe you can isolate which switch bank is going bad.

Sherm117 · Jan 5, 2020

PermanentTourist said: ↑

It was like three years ago so I don't exactly remember. From what I remember, from the triangle flasher control unit there are connections going to the rear switches, and the two Banks of front switches. I disconnected the one going to the rear switches. I forget which one it is.

Try disconnecting one connection at a time and see if the problem goes away. That way maybe you can isolate which switch bank is going bad.
Click to expand...

Thank you for your reply.

IMSITTINGINYOURCHAIR · Jan 7, 2020

I discovered these switches could be moved around when I drove for swift back in '15, just do it with the key off and master off to prevent setting history codes in the ecm and sam. I moved the dome light switches up front since I am a solo driver, I just need to get an extra switch for the over the bunk light since I always leave that on... also, if the headlight switch fails or is left unplugged from the back of the master the headlights default to on.

I_stallion · Apr 25, 2020

mhyn said: ↑

if you would have DL you could diagnose this problem within 5 minute.
Click to expand...

Hey there! What is “DL”? I followed this thread bc I am having a problem with wiring to a fuel gauge.

I_stallion · Apr 25, 2020

mhyn said: ↑

if you would have DL you could diagnose this problem within 5 minute.
Click to expand...

What is a “DL”?

rachi · Apr 25, 2020

PermanentTourist said: ↑

Update: success!

I downloaded a very dense and technical manual about the cab electrical system, and learned that:
A: these are called MSF switches on a CAN bus. (Sorry mr. Uncleal, not J1939. That controls the more serious stuff like the engine.)
B: the box with the flasher triangle is the MSF Master. It controls all the other so called slave switch modules by a three wire connector. It has multiple inputs for those connectors.

My particular version of the master controller seemed to have two slave switch connectors going into it: one for the important front switches and one for the rear ones. So I tried pulling out the rear switch connector and voila! All the front switches came back on! The check engine light and the beeping went away, and my engine brake works again.

I guess the signal wire running to the rear switches has a short somewhere, and it was confusing the whole digital system, flooding it with white noise so it couldn't "hear" all the other switches. I will have to track it down eventually, but meanwhile I can keep running! It'll be a bit annoying not being able to control lights from the bunk, but that's a project for some other day, when I'm stuck somewhere waiting for freight and bored.

I am so relieved, I was afraid that I fried something expensive. Now time to put the truck back together and go to sleep.
Click to expand...

Its a good feeling when you figure out a problem like that. Now, even if your a company driver, you should get intimate with your trucks emissions systems because only a matter of time untill some sensor acts up and throwing it all out of whack.

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Dashboard electrical issue, trying to fix it myself - FIXED IT (kinda)

Dempsey7771 Bobtail Member

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Dashboard electrical issue, trying to fix it myself - FIXED IT (kinda)

Dempsey7771 Bobtail Member

Sherm117 Light Load Member

PermanentTourist Heavy Load Member

Sherm117 Light Load Member

PermanentTourist Heavy Load Member

Sherm117 Light Load Member

IMSITTINGINYOURCHAIR Bobtail Member

I_stallion Bobtail Member

I_stallion Bobtail Member

rachi Road Train Member

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