Taillights ,arenot working don't know where the grounds are located on the moter home

In about 1985 automakers started using plastics for tail light assemblies and ran a separate ground to the most convenient location for them, " the engineers". so run a wire to ground that you can reach and attach it securely. they basically use the same thing, but over 10 years they rust and lose contact. Also using that same ground make sure you are getting power to the light from the switch. Ignition on, signal on, and no light or power indicates the turn signal assembly in the steering column is broken and must be replaced. not difficult for mechanically inclined persons. tools needed- steering wheel remover tool, and ignition lock ring depresser.

Find where the ground wire for that left taillight grounds to the body remove the screw and clean that ground, otherwise if the taillight assembly uses a printed circuit could be a break in the printing, replace the whole assembly if thats whats going on.

check the brake light switch located on the top of the brake paddle also check the butten on it if its stuck in.

Any wire on any of the taillights that is brown is power for the taillights. Any wire that is yellow or yellow w/black Is the stop/turn signal power wire. Any wire that is black is ground. Hope that helps.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The taillight circuit includes the front parking lights.
You would need to take the bulbs out and check each socket for a short to ground.

earth wire will be in the back of vehicle near the lights

unfortunately with conversions the manufarcturer quite often doesn't provide documentation . you should have 4 wires to each light, one ground , one taillight, one brake-signal, and one reverse light, best to find the ground first, then you can locate the others, if you have trailer wiring its white ground, yellow left turn, green right turn and brown taillight

there are usually two hot wires going to the wiper motor .. also a ground strap that may be bad ... one of the hot wires is always on if the key is on ... that for homing the wiper blades when you turn them off .. the other power input is from the wiper control circuit .. its only on if the wiper switch is turned on .. if you have power on the homing input then that wont do anything unless the wipers are not in home position .. if you have power to the "run" wire of the motor and the ground is good then the motor should run unless its defective .. you can put a jumper cable from the ground of the wiper motor to the engine block or battery neg, to check if the ground wire is causing the trouble .. that happens frequently in some models but not sure about your E250 ...

Yes, the timing of the start of the problem indicates it's something that happened then. It could be a wire on the assembly was pinched or covering damaged by a screw holding it in place. How quickly did it blow the 1st replaced fuse? Let me know how u make out.

the fuse for the tail lamp/instrument cluster may be bad.