Rig Info: 1990 E350 – Ambulance Package, 7.3 IDI Diesel, E4OD

I have a handful of electrical gremlins I need help tracking down. I am an electrical-idiot so any help is appreciate. I am unsure if they are all related or independent problems.

1) When I bought the van, the dash light would blow fuses as fast as they could be put in. Removing the aftermarket stereo cured this. I am currently rolling around without a stereo. Where should the radio be grounded?

2) Red Parking Brake Dash Light – This light will come on randomly when driving. The parking brake is not depressed. This short seems to be associated with the cigarette lighter. In addition to coming on randomly, if my phone charger is plugged in when starting the engine the light will become illuminated. The light stays illuminated until the charger is removed. Re-plugging in the charger does NOT cause the light to come on. Where is the e-brake grounded? Where is the cigarette lighter grounded?


3) Yellow Rear ABS Dash Light – This light comes on randomly while driving without rhyme or reason. Brakes seem to be functioning properly, though I have never tried braking hard enough to cause a rear skid on public roads for safety reasons. Any trouble shooting tips?

4) Marker Lights – When the brake pedal is depressed, all of the marker lights and dash are illuminated. This is true independent of the ignition key position, meaning the lights come on if the key is in any of the off/acc/on positions. The rear brakes also illuminate.

5) I have read that these vans have multiple chassis grounds. Can anyone help me locate where these are?

I have tried using the search function for each of these, without much luck. Sorry if these topics have been beaten to death, please attach a link and I will read up. Electrical problems are my weak point, so elaborating on exact wire locations, and colors will help. Thanks in advance for any trouble shooting tips!

 

These all sound like seperate problems. The radio is grounded thru a ground wire, and the antena lead. Brake light should have nothing to do with the cigar lighter, is the brake fluid full? A bad bulb could cause the marker lights to come on with the brake lights, the filament could be touching and bake feeds the marker circuit, This was an Ambulance, the wiring in that truck could be a horror story, unless the person who made it street legal did a real good job. Have not seen to many though. The yellow abs light could be a sensor going bad in the diff. Sounds like multiple problems, take one on at a time, and pickup a wire diagram for that year and model so you know what color wires and the grounds are. Good Luck

 

The stock radios have a metal blade bolted to the back side that plugs into a U-shaped metal bracket which is bolted to the body. I'm not positive without reviewing schematics, but I'm pretty sure the radio is grounded through the wiring harness as well.


A lot of times the parking brake mechanism is worn, or the equalizer out of adjustment to the point the switch will illuminate while driving. Pull the release lever and immobilize same and see if that problem is solved. That switch could be worn out/damaged, as well.


RABS problem should be throwing codes. Kinda sounds like a wiring problem.


Ground strap: dash frame to PCM (passenger side floor area beneath HVAC unit.


Ground lug: Negative battery cable at passenger side fender apron.


Ground strap: back of cab (passenger side) from cab to frame. Look near O2 sensor.


Additionally, there should be two black leads coming off the engine compartment wiring harness bolted into the cowl area, near the hood hinges. Also, the negative battery cable needs to be attached to the engine block where FORD intended; NOT to a water pump bolt ... or, an intake manifold bolt etc.