1997 Sierra diesel - battery leads came off while driving - no electrics - what's fried?

[davidzeballos]

1997 Half ton - Sierra - Diesel - Coming into work - down a long logging road - I was coming down the final hill and suddenly all the dashboard lights went out and I had limited control. Freewheeling down a hill. Very scary.
Managed to stop and looked under the hood. The battery leads had come off the front right battery. Reattached the leads - no motor action sounds.
I was probably driving without power for no more than a minute.
A friend tested the batteries with a volt meter and said there is still life in the batteries.
I am in the middle of nowhere and want to avoid a tow if it is at all possible to get one.
What might be fried?
The alternator?
The starter?
Anything else?

Any advice appreciated.

 

[Road Trip]

1997 Half ton - Sierra - Diesel - Coming into work - down a long logging road - I was coming down the final hill and suddenly all the dashboard lights went out and I had limited control.

...Managed to stop and looked under the hood. The battery leads had come off the front right battery. Reattached the leads - no motor action sounds.

Glad you were able to avoid injury. Could you please elaborate on the 'no motor action sounds'?

Is there dead silence? Not even a click? Or is your engine cranking over but otherwise no audible
cues that it's actually trying to start? Please be as descriptive as possible, the smallest detail might
hold the key to figuring this out remotely.

Just trying to figure out if we're troubleshooting a 'no crank' vs 'no start' scenario. 2 different paths.

 

[davidzeballos]

there is one click - lights on - then no engaging / wouldn't turn over.
then if you tried it again - thirty seconds later - there was no click and no lights - no nothing - excuse the double negative

thanks in advance

 

[Road Trip]

(Others please jump in if I'm missing something obvious)

To me, the total loss of *everything* (lights, starter, etc) tells me that
this issue will be traced to a loose ground that affects everything.

(This is a much higher probability than you blowing multiple fuses at
the same time.) NOTE: If your coworker just checked the voltage
at both batteries, they can show a voltage but not be able to deliver
the kind of current you need.

We've got to get your lights to stay on first, and then address whether or
not the engine will spin over fast enough to fire up. And since you're a
diesel, we have to support the glow plugs AND crank that motor over.

Please verify any/all electrical connections under your hood. Meanwhile I'll
see what I can find in GM service manual for your truck.

More asap.

 

[Road Trip]

1997 Half ton - Sierra - Diesel - Coming into work - down a long logging road - I was coming down the final hill and suddenly all the dashboard lights went out and I had limited control.

What might be fried?

The alternator?
The starter?
Anything else?

PS: Because you are a diesel, I am assuming that you have a dual battery installation?

First, the starter was not 'in circuit' during all this, so no worries there.
As for the alternator, we've yet to figure out if it was forced to work into an open circuit
(which could cause the voltage across the output diodes to skyrocket) ...so as of right
now I can't say for sure. But since you mentioned 'limited cotrol' this makes me think
that everything in the engine bay came to a halt, including the alternator, so it's probably still
OK.

But losing everything after driving down a logging road makes me think that a connection
loosened up. Look carefully for a loose connection. More in a moment.

 

[Road Trip]

In order to give you a better idea of where to look, here's a listing of the
underhood grounds for your truck. Please verify the following:

* G101
* G102
* G103
* G104
* G105

And it goes without saying that both batteries need to be securely connected,
both positive & negative.

You must be registered for see images attach

By the way, since the headlights are on a "Always Hot" circuit, what is their
behavior when you try to start your engine?

* On until the engine starts to spin over, then go dim?

* On brightly no matter if the engine is being cranked or not?

* Always dim?

Let us know what you find. Fingers crossed you find it!

 

[Road Trip]

Here's the physical locations of G101, G102, and G103. Please note
that losing G101 (on the sheet metal near the passenger side battery)
could explain the loss of lights in addition to everything else.

You must be registered for see images attach

 

[Road Trip]

And here's G104 & G105, attached to your Diesel:
Make sure everything's clean & tight.

You must be registered for see images attach

 

[Road Trip]

And if verifying all the grounds you still don't have any luck, then here's the page
that shows how the big positive power is delivered to the Underhood Fuse Block,
the alternator, and the starter:

You must be registered for see images attach

The answer is in these replies somewhere. By the way, have you recently noticed any weird behavior by
the voltmeter in your instrument cluster?

 

[GoToGuy]

How did the leads come off? Both positive and negative ? The positive contacting any bare metal area, that could be catastrophic. A rough trail ? Did you test the fusible link?