Electrical Gremlis:

[Mikes Bikes]

Having issues with my M1084A1

History:
Truck had intermittent no start issues in the morning. Slave start and it would be okay. Traced problem to the light switch, replaced and was okay.

Current symptoms.
Starts and runs
Trans is fish eye when running. Code 3500
Cooling fan over tandems runs continuously with ignition on.

Gauges work with ignition switched on. As soon as it fires up, gauges peg at nothing, or max. and trans goes to fish eye.

Lights all work with ignition off or tuned on. No lights when running.

Alternator showed: Green in 28V, Yellow on 14V. Replaced batteries and resolved this issue.

All other issues remain.

Any thoughts

 

[NDT]

Check voltage levels here there everywhere. Especially check the stupid LBCD under the spare tire. Volts in and out.

 

[Ronmar]

Gauges and trans are 24v, sounds like you are dropping 24v after startup. A bad power/ground connection leading up to the power panel could cause volt drop as soon as you try and pull current thru it. The lbcd/ppd connections being out in the weather are likley candidates… could also be bad contacts on the 24v ign relay?

I often find that concentrating on one issue will kill the root cause of many.

CB-43 and CB-79 provide 24v batt and ign to the trans. I would measure voltage at those circuit breaker positions while it is running. The best way to do this is pull the CBs and install comparable value automotive blade fuses. Then you can measure the voltage on the little metal test points on top of the fuse WHILE it is in operation.

You should see voltage within about half a volt or so, of what you see at the alternator output terminals…. If not, work your way back thru the circuit until you do.

Don't forget ground is part of the circuit
Also don't forget voltage is NOT good until it is measured good under operational load…

 

[Mikes Bikes]

Well, the Steel Soldiers Trouble-Shooting Collective comes through - Problem solved - Started with the LBCD and worked my way through the breaker/circuit panel. Disassembled and cleaned every connector, cleaned and re-tightened every lug. Did not have my VOM, so I don't know where the culprit lies. But the truck and its crew will be going to the job site tomorrow!

THANK YOU!

 

[Ronmar]

Well, the Steel Soldiers Trouble-Shooting Collective comes through - Problem solved - Started with the LBCD and worked my way through the breaker/circuit panel. Disassembled and cleaned every connector, cleaned and re-tightened every lug. Did not have my VOM, so I don't know where the culprit lies. But the truck and its crew will be going to the job site tomorrow!

THANK YOU!

No VOM! You are literally frikkin killing me…

 

[ramdough]

Buy one that lives in your truck. Preferably with a backlight. And get some alligator clips.

That is what I wave in my tool kit.


Sent from my iPhone using Tapatalk

 

[mechanicjim]

cleaning terminal connections tends to kill the big gremlins and leave the little ones to be hunted down. the little electrical gremlins like to be the cool kids and smoke things.

 

[NDT]

View attachment 864627

cleaning terminal connections tends to kill the big gremlins and leave the little ones to be hunted down. the little electrical gremlins like to be the cool kids and smoke things.

Nice how TACOM tried to blame lack of PMCS for failures really due to the CRAP design Leece Neville charging system.

 

[Ronmar]

Nice how TACOM tried to blame lack of PMCS for failures really due to the CRAP design Leece Neville charging system.

Yep the LBCD and disconnect relays were a bandaid put in place because of the root design problem, the gross mismatch of a 240AH battery with a 100A combined alt…

 

[Suprman]

Trans cats eyes is non communication between keypad and tcm. Usually its a bad tcm