2nd Gen Non-Engine/Transmission Major electrical short - help!

[RPost]

I noted a "check gauges" warning just as I pulled into my garage and noted low voltage just before I shut off the engine. Next time I went to use the truck, it was stone cold dead. After disconnecting the batteries, I used a continuity tester on the positive battery cable and found it at ground potential. The separate secondary small cable that appears to go to the intake air pre-heat system is also at ground potential even though I disconnected it from the primary positive cable. Any ideas on how to find the short by a process of elimination? I have considered reconnecting the now-charged batteries and trying to restart the truck to see if something fails, but that probably would make some sparks and maybe worse.

 

[Phil Stuart]

I would first disconnect the wires feeding the grid heaters (both of them) to isolate that part, wrap them in tape just for safety. Check the relays for the heaters also. Isolate / disconnect as many components as possible and hopefully that will help. Use a Multimeter if u have one, they are invaluable.

Maybe other folks will have ideas also.



Phil

 

[fest3er]

Look for melted stuff on the intake manifold. If found, at least one of your intake heater relays stuck 'on'.

https://www.turbodieselregister.com/forums/2131910-post6.html

 

[madmanmanick]

connect the batteries and due the test, but this time pull out one fuse from the fuse panels at a time. whichever one of them has the problem it will go away. hope this helps.

 

[BHanna]

It could also be a bad alternator. The low voltage happening suddenly while you're driving is pretty typical of that.

 

[flyby night]

what are you defining as potential to ground? You will not show open by checking resistance between the positive cable and ground. You will be reading the resistance through various components through the system. There are things that are always drawing small amounts of power in a normal condition such as radio memory, engine ecu, etc.

 

[RPost]

I should have said that there was less than 70 ohms resistance (the resistance below which the continuity tester beeps) between the disconnected positive cables and ground. I was assuming that various circuit components with a path to ground would have more resistance than that and failed to consider continuous draw for the items you mentioned. Thanks to those who responded with ideas.