New to the diesel life and need some help. I have a 1990 D250 Cummins. Here is my problem. There is a fusible link coming off the positive side of the battery which goes just before the fire wall and splits in two (Pink and black, & Red wire). It then goes into pins 49 & 50 of the firewall connector. Then both wires go from there to a small black box with two connectors that sits on top of the steering column under the dash. All wires are good and not grounded out anywhere and all connectors were cleaned and dielectric grease put in.

So if I'm running my AC and playing the radio and use any other option that requires power ie. turn signals, power windows, cig. lighter, etc the fuse thats in the link right by the battery blows (30a)and the entire truck cuts off and the only thing that works is the door buzzer and nothing else. One of the wires in the small black box on the steering column goes to the fuse box for the main feed. My question is, is there just too much power trying to be drawn on an old system or is there something wrong because I'm now at a loss. I have also replaced both battery cables, battery, regulator, and alternator due to issues.

Any serious help is much appreciated.

 

In short your answer is YES.

These trucks are better served by re configuring the fusable links, and separating the heater blower, the headlamps and other high draw items into separately served power sources. Most of the guys with electrical problems have installed sub panels, which draw power from the battery, to a fuse, then to the new sub panel. We then run accessories from that new sub panel, which is usually mounted to the inside fenderwell somewhere.

The headlamps should be separated first into new direct powered relays, eliminating the draw through the steering column. You will see in my signature that I have something called "Jim Lane relays". he's the genius here who created a thread showing us knuckleheads how to put our headlamps on relays, and eliminate the draw through the ignition switch. This prevents the fuse panel above your brake pedal from catching fire, or melting away, like a lot of ours have. I was lucky enough to have a truck that the fuse panel wasn't heated up, or melted and I've had no issue since.

The heater / blower motor can also be placed on relays, but that's a bit more complicated . Jim Lane did a tutorial on that as well. I have fuses where my fusable links were, and sub panels that run my accessories (radio, accessory spot lamps, accessory ports, etc. This allows my heater blower circuit to remain nice a cool, as the other draw items have been removed and relocated to the new sub panel.

I had some electrical gremlins where I would get a intermittent failure of my fuses where my fusable links were. Turned out, after countless hours of fiddling around, someone gave me the hint that it was the wiring in my door bulkhead that could be a problem. Since my LE dodge has the power windows, mirrors and locks in there, the fuse kept blowing on that circuit. When i unraveled the covering on the wires between the door and bulkhead pillar, the wires were cracked sheathing on each individual wire, and were short circuiting the system out.

Biggest problem with our trucks is poor grounds. Poor grounds from the negative cable to the radiator bulkhead, to the engine block. Block to frame, Block to firewall. All get corroded, and should be annually inspected and cleaned (here in the rust belt). YMMV, depending on where you're located.

Jim lane, master guru, convinced me to add a secondary set or two of grounds from the negative terminal to the alternator bolt mount, and from engine to frame, etc. Can't have too many grounds.

Separating the excessive draw into sub panel, and separating them individually, fused, and / or relayed is the way to fly.

All this info is here, already printed, for you viewing in the FAQ Sticky. Lots of pictures to boot.

The reason the truck "cuts off" is that (most likely) the circuit which powers your FSS (Fuel Shutdown Solenoid) relay is being tripped, and shutting power down to that circuit The FSS is a solenoid, located on your main injector pump, on the driver side of the engine which shuts the engine off, by stopping fuel to the injectors from continuing. The connector usually goes bad on them, and lots of us have fixed that by replacing the spade connector with ring connectors, which can't wiggle loose while driving. If power remains to the FSS, the engine runs, and will continue to run, regardless if the rest of the truck has burned to the ground, and is a smoldering pile of rubble. Once that 12V stops energizing the FSS, the engine shuts off.

Best to you.