Electrical gremlins out of control. - PeachParts Mercedes-Benz Forum

ascalise · #1 11-18-2007, 10:39 PM

I just bought a 240d and have been trying to work through the bugs. Here it goes, i'll start with the blinkers. Left and right work both front and back with blinker switch. If i turn the hazards on they'll work sometimes, sometimes they won't, so i'm assuming its the switch or flasher relay. going to replace those tomorrow. I've already replaced all fuses and cleaned up fuse box. Ok, now for the fun part. When the headlights are on is where the fun starts. BTW, all of my problems are in the rear of the car. With headlights on i get one dim light on the pass side that seems normal along with a the right indicator on SOLID (dim green right arrow on instrument cluster) and on the drivers side i get the tail light on and the brake light on. If i step on the brakes bright light on the drivers side shuts off and the tail light on the passenger side gets brighter. With the lights on or off, I only have the drivers side reverse light. If i put the light switch on the left parking lamp position i get no parking light in the front, and both outer red lights in the back lit. If i put it on the right parking light position i get no parking light in the front and the right reverse light lit. Ive been going through the forums for a day and haven't seen anything even remotely close to this discussed. Anyone have any ideas? BTW, bulbs are all good or new in the back and connections all look brand new as well.

pawoSD · #2 11-18-2007, 10:43 PM

It sounds like you have some loose ground connections, I'd start by looking and checking all of those in the dash, on the headlight switch, and in back on the light bars etc....ground wires on these cars are always solid brown.

ascalise · #3 11-18-2007, 10:48 PM

I just had the gauges out of to fix the rheostat and looked at the ground there. They were tight and clean. On the light bars the only ground is a brown wire to each of the bars that goes through the harness and plug, where else could i check?

ascalise · #4 11-19-2007, 04:07 PM

Anyone? i checked the harnesses and the light bars they look like new and there is nothing broken.

pawoSD · #5 11-19-2007, 05:18 PM

You said its when the headlights are on, I'd check to make sure all wires are proper on the headlight switch (theres several of them). And check the headlight assemblies and marker light plugs etc to make sure they are all ok too. Maybe try unplugging one headlight/marker/light bar at a time while the problem is happening to see if it goes away? Do step by step checking with the stuff turned on so you can see if the symptoms change, if they do, you may have found all or part of the problem.

JimSmith · #6 11-19-2007, 06:23 PM

Quote:

Originally Posted by ascalise

I just bought a 240d and have been trying to work through the bugs. Here it goes, i'll start with the blinkers. Left and right work both front and back with blinker switch. If i turn the hazards on they'll work sometimes, sometimes they won't, so i'm assuming its the switch or flasher relay. going to replace those tomorrow.

How did that work out? I would have replaced or at least tried to clean, the hazard switch before going to replace the relay.

Quote:

Originally Posted by ascalise

I've already replaced all fuses and cleaned up fuse box. Ok, now for the fun part. When the headlights are on is where the fun starts. BTW, all of my problems are in the rear of the car. With headlights on i get one dim light on the pass side that seems normal along with a the right indicator on SOLID (dim green right arrow on instrument cluster) and on the drivers side i get the tail light on and the brake light on. If i step on the brakes bright light on the drivers side shuts off and the tail light on the passenger side gets brighter. With the lights on or off, I only have the drivers side reverse light. If i put the light switch on the left parking lamp position i get no parking light in the front, and both outer red lights in the back lit. If i put it on the right parking light position i get no parking light in the front and the right reverse light lit. Ive been going through the forums for a day and haven't seen anything even remotely close to this discussed. Anyone have any ideas? BTW, bulbs are all good or new in the back and connections all look brand new as well.

The issues with the rear of the car indicate to me you have several problems. Did the lighting system exhibit this peculiar response before you took to replacing the fuses and cleaning the fuse box?

If not, I would look there first and see what you might have done, as the fuse box is the only place where all these connections come together other than the light switch. If the problem did not exist before you worked on the fuse box, and you did nothing to the light switch, or anything below the dash on the driver's side, it would seem to point the finger at the fuse box.

If the problem existed as you described before you worked on the fuse box, it would seem the light switch is a likely candidate problem. This is a pretty significant element in the overall circuit design, and you will need a schematic to show you what is what on the switch.

The apparent abberant connecting of the various lights in the rear should be traced back to the applicable fused circuits in the fuse box. Recheck the installation of the fuses, and make sure no loose old fuse aluminum or copper shards have become lodged between fuse holders on on the connections to the fuse holders. With the appropriate fuses removed, check the lighting system responses (study the fuse holder list of circuits, and you will probably be able to find a circuit with odd behavior that requires two fused to exhibit that behavior - like the left and right side parking light switch - for both rear lights to come on, two circuits have to be energized). It may help figuring out where the problem might be.

But, you have a mystery on your hands. Good luck, Jim

Another issue seems to be with lights changing brightness under different circumstances. This may be an indication you have multi-filament bulbs in the rear sockets as I don't understand why the brightness would change if the voltage stays the same. If the brightness changes are not due to the wrong bulbs installed, there most certainly are several misrouted connections at either the fuse box or the light switch.

jbach36 · #7 11-19-2007, 07:04 PM

Even though the fuses might look good, replace them all, preferably with the copper ones. The metal ones they use pit and chalk. So if they're not carrying the electrical current properly, it builds up heat and resistance on other components. Replace ALL of them with new ones.

jeff

ascalise · #8 11-19-2007, 07:15 PM

Symptoms have been the same since who knows. I bought the car like this then started with the hazard switch and relay. I took them both out and cleaned them. I then took out the fuses and cleaned with contact cleaner and a wire brush. I just went and bought ALL new copper fuses to replace everything under the fuse box cover. As far as symptoms, nothing has changed. I did just buy a new flasher relay and flasher switch because i know i have a problem with the flasher, they work then done, and so on... I'm going to work on that in a bit.

ascalise · #9 11-19-2007, 08:32 PM

Just replaced all fuses with new copper ones, replaced flasher relay, and replaced flasher switch. Same symptoms.

ascalise · #10 11-19-2007, 09:48 PM

Just checked grounds in the trunk below the power antenna and cleaned them up and replaced the bulbs. I even grounded each tail light strip to a nearby bolt. I also checked the front signal bulbs. For some reason now my left blinkers blink really fast and my right ones blink slightly faster than normal. If i run the 4 way flashers they all blink at the speed they should. I'm stumped, there has got to be something seriously wrong somewhere in the car. Also, this problem just started, my stupid radio isnt picking up FM signal, its acting like there isn't an antenna conneted. Double checked that, its connected on both ends.

ascalise · #11 11-24-2007, 06:49 PM

Update:

I replaced the main rotary headlight switch swapped from another car and got the same results. I have no idea what is left. I'm sure someone has had this kind of problem. Anyone?? I need to get this fixed so i can get the car inspected and on the road. Thanks in advance.

ascalise · #12 11-26-2007, 08:02 PM

Figured out what the problem was and dont know why in the hell anyone would do this but, the pins in the plug going to the RR light bar were all mixed up. I took the connector apartand matched the wire colors from the harness to the light bar and everything is back in working order 100%. What a pain, after everything i checked and replaced