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 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 – 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!

 

I don't know a lot about vans, but will try to help you out the best I can!

1) The stereo was most likely installed incorrectly. It should ground somewhere behind the dash. The power to the stereo should be a fused line that the original stereo would have had, though I don't know what the "ambulance package" would have differently. There should be a wire on the dash light circuit that illuminates/dims the stereo when the dash lights come on/dim. Its possible the PO hooked this wire to the stereo's main power which would explain the fuses blowing.

2) There might be a dash ground missing or broken. Like I said, I don't have a van so I have no clue where exactly to look.

3) The ABS on these trucks (err vans too?) were marginal from the factory. Most people disconnect the ABS system if its not working right, or ignore the light. If the brakes work fine, I wouldn't worry about it.

4) This sounds like there is an issue with the grounds for the brake lights. I would pull the lights and trace the ground wire in the rear of the van. Without a good ground, it is grounding through the marker lights, which also then pushes power back to the dash lights. Hmmm... maybe that is related to the issue you had with the stereo as well?

5) Sorry, don't know anything about vans

 

Thanks for the reply! I will update as more info rolls in. I will also post in the van section, hopefully there are some folks there who have experienced similar problems. Thanks again!

 

It sounds like most of the issue may be a bad bulb or poorly wired trailer plug if so equipped, causing a back-feed from the brake lights to the marker lights.
Being a conversion, it may have a junction box somewhere near the front or rear inside with the junctions for all the taillight and overhead lights.

 

Prime suspect, in my book. Dunno what the rear stop/tail/turn lights would be on an ambulance, but if the use the old 1157 bulbs with the round base, and they're not installed correctly (or if someone put a single-filament bulb in the base, which is not impossible to do), that would cross the parking/tail/marker circuit with the brake light circuit, basically make them all one circuit. If it uses the "newer" 3157 wedge-base bulbs in the rear, they're less susceptible to this, but any stray metal object in the socket that would cross-connect the two circuits would do the same thing.

 

I have an update on the brake lights.

Upon further testing, I realized that the brake pedal seems to illuminate the running light portion of the brake light. When the brakes are depressed, the tail light is dimly illuminated. When the head lights are on, the tail light is dimly illuminated (as you would expect), but when the brakes are depressed there is no change in the illumination (with the head lights on).

I checked to see if a single filament bulb was used instead of the correct dual filament. Both sockets were heavily corroded. The first was so bad, that the bulb was fused to the socket. I replaced it with a new 1157 socket and it is "working" as described above. I am having trouble changing the second socket because after taking it apart it is no longer getting voltage?! Weird.

In addition to this, there is a trailer wiring kit that has been added. There are 5 wires, black, yellow, green, blue, white. The blue and white wires are clipped 5 inches from the plug and connected to nothing.

With this new information, how should I proceed? What causes the brake pedal to illuminate the running light instead of the brake light? Any suggestions in tracing the short for the second brake light?

Regarding the trailer harness: What should the blue and white wires be connected to?

Thanks in advance for taking the time to reply. I am in over my head!

 

For trailer connections, white is generally ground and blue is electric brakes (trailer brakes, NOT brake lights). However, assume nothing as it may have been wired wrong in the first place, or just random color wires were used.