Driving along, it goes dead. I pull to the side of the road. Dash lights dead. Radio dead. I can hear clicking, and the dash gauges twitch. 40min later, the dash gauges seem to do a reset. I turn the key, all is good and I get home.

Next day, starts normally. I rev the engine. It does, then same problem, goes totally dead, dash gauges twitch. Then nada.

This is a modified EGR vehicle with 200K on it. Recent oil change. Reliable. Not towing, no real load.

Feels to me like a floating ground, but I'm all ears before I dive under the truck and start tightening things.

One small side note: The CEL light's been on because of the mod'd EGR. That light, as well as the usual ABS light have gone out; leads me to think that the ECM has somehow reset, too.

Thanks in advance,

Tom W9YW

 

When is the last time the batteries were fully charged manually, and load tested (individually)?

 

Charging it now; was only slightly low in V (11.8)

 

11.8 at rest is VERY LOW (NOT just slightly low).
Also, voltage by itself does not tell the entire story!

https://preview.redd.it/abkr3qzb4qe7...=webp&6d679512

 

 

Thanks for the info.

I brought the state of charge to 12.8VDC. I'm hearing a relay chattering, not the solenoid. There was something that reset. It started. Went for a few blocks to another destination.

Then, it had the symptom of wonky dash lights/gauges. I charged it again at that destination, even though B+ measured 12.7. It started normally after what appeared to be another reset. CEL and ABS light came back on (this is normal for the settings).

I'm thinking it's the A F or K relay. I reseated all three. Other advice appreciated. The body/chassis grounds are looking good. I think the problem will occur again.

Thanks.

 

I suggested load testing each battery earlier ...........................
Take them to an appropriate place of business and have it done (tested individually).