Electrical issues 1990 HDT 81

[CountFloyd]

So I’ve been loosing electrical function on my 80.
the first indicator was the head lights. I thought it was the relay, but looks like a voltage drop off the fuse/relay panel.
then I noticed the glow plugs/fuel heater isn’t working. Nor are the dash lights or rear window defrost.
has anyone experienced symptoms like this?
sounds like the type of thing caused by bad grounding too me.
i replaced and cleaned all connections at the batteries. Cleaned the glow plug fusible link, and other grounds.
the cold is making troubleshooting difficult...
Thanks for reading.

 

[roscoFJ73]

Have you checked the ground strap on the engine at the engine end and the other one that bolts to the chassis? They often get corrosion and dirt between the surfaces.

Have you tested the voltage before and after the fuse box?

Are your windows going up and down normal speed?

 

[CountFloyd]

I didn’t check the engine ground yet. And the windows work like $hit. Especially in the cold.
I check from the fuse/relay panel to the battery and there was a voltage drop.
I took the truck to a shop as I had to leave town and it’s cold out. They didn’t have any luck so I’m back to square one.
that’s another story...

 

[SHREDwagon]

Edit: Deleted as there's no hope

 

[CountFloyd]

I’ve replaced the batteries, terminals, and alternator. I know it’s charging.
it’s just a matter of laying in the snow.

 

[roscoFJ73]

I’ve replaced the batteries, terminals, and alternator. I know it’s charging.

Have you inspected the earth lead at the engine block end? They can get pretty corroded and dirty and are often missed when diagnosing low voltage head aches.

 

[CountFloyd]

I just got home and am gonna have another go at it tomorrow. Thought I would try using a set of booster cables to check which ground was bad.

 

[ozcrusier]

Test or replace the fuseable links.

 

[CountFloyd]

I cleaned the one side when I changed the terminals.
is the left side battery only for starting?