E500 Haunted Electronics - PeachParts Mercedes-Benz Forum

mbsteve · #1 07-09-2004, 11:11 AM

HELP!!!!

I have jsut had the most unusual set of issues pop up in the last two days.

1. Lost the outside (ambient) temperature display on the instrument cluster. The backlight is lite, but only by moving my head all around can you sometimes see the numbers in the LCD.
2. In the afternoon (following two re-starts of the car) ambient temperature gauge is still not displaying correctly, and now the fuel gauge starts fluttering when it is down to 1/4 tank. This goes away after filling up, but will it happen again? Sure enough it does the next day when I am down to the 1/4 tank mark - only not as much fluttering and it goes away again after I fill up again.
3. Last night is the winner. At 4:30 AM the Radio is suddenly blaring loudly - no key in the ignition. It came on like an alarm clock. I could not figure out where it was coming from until 8:30 this morning. Reached in and turned it off - antennae drops down and the noise stops. Car still manages to start so the battery is not fully drained.

What is going on and where do I start? Fuses? Relays?

Thanks

Steve

miktvk · #2 07-09-2004, 01:58 PM

Places to start:

Check fuses.

Check voltage on battery with meter if possible. Healthy battery reads about 14.5 volts when engine running.

Through personal experience I have found that low voltage, either through sick alternator or dying battery creates bizarre electrical behavior well beyond the old dimming lights symptom. Just before it gets really ugly, all the warning lights in the cluster will go beserk, and the radio acts really weird, if I recall correctly.

What's the condition of your engine wiring harnesses? one of wires (or more) may be grounding out?

mbsteve · #3 07-09-2004, 02:39 PM

Thanks for the response and suggestions. I will measure the voltage when I get home in a couple of hours and see what it says.

My car supposedly had a new wiring harness in 1999. The car is gargaged, cleaned religiously, does not see salted roads, etc. i will also make a cerefull (as best I can) inspection of the wiring harness. Are there any particular spots I shiould be expecially aware to be looking?

Thanks

aldedmon · #4 07-09-2004, 03:23 PM

Quote:

In the afternoon (following two re-starts of the car) ambient temperature gauge is still not displaying correctly, and now the fuel gauge starts fluttering when it is down to 1/4 tank. This goes away after filling up, but will it happen again? Sure enough it does the next day when I am down to the 1/4 tank mark - only not as much fluttering and it goes away again after I fill up again.

So you filled 'er up and then the next day, you were again back down to a 1/4 tank??? Either Gas prices must be pretty cheap in TN or that's some lead fook you got there

mbsteve · #5 07-09-2004, 05:19 PM

Aldedmon

Prices just across the border in Georgia are pretty great - I paid $1.87 for premium. Was making a terrific one day shot down to Agusta Georgia (about 550 miles RT) and always fill up in Nations cheapest gasoline State.

Unfortunately their gas appears to come with gremlins - even though it always gives me 20 mpg.

miktvk · #6 07-12-2004, 08:34 AM

mbsteve,
hard to believe that the new harness would also be defective, but one never knows. I would check the wires that branch off the harness to the fuel injectors, I guess they would be under the shroud and sitting in the area of the intake plenum, where its real hot.

You would have to split open the outer sheathing to have a look at the actual wire insulation. If its bad there its bad elsewhere.

Can't hurt to have a look.

mbsteve · #7 07-12-2004, 10:52 AM

Thanks for hanging in there with me.

Voltage is correct at the battery (14.2 on my meter), and all fuses are good. I will remove the air cleaner and check the wiring underneath and see if that does the trick. I have had no sudden radio turning on problems but the gas gauge is still flaky and the ambient temp gauge almost came back to life over the weekend but then died again this morning.

What do you think of this being caused by a shorting fuel level sensor? I do not know where it is on the tank, but presume there has to be some type of sendiong unit. Any ideas on how to test or check that out?

aldedmon · #8 07-12-2004, 04:24 PM

I had the same thing on my 92 400E. It is a reoccuring problems on the W124's. I replaced the fuel tank on my 400E with the larger 500E tank(18.5 VS. 23.1 gals) The tank came with a fuel sending unit. After replacement, the quirky/jerky movements were no more. The sending unit is located on the top of the tank. You just take out the trunk lining(the tank rests against the back seat) and you'll see it at the top towards the center of the tank.
Before replacing it, try cleaning off the contacts of the unit and those of the wire connector. Use an abrasive, like a wire brush/sand paper or something. You'll need something very slim to fit into the connector. Its the same sore of problem that causes the cooland light to dimly glow on these cars.(if you haven't encountered that problem yet....just hang on, you will). For that problem, I recommend that you replace the coolant level indicator(its the little metal dohickey that the wires plug into at the bottom of the coolant reservoir)

Pleasant driving

stevebfl · #9 07-12-2004, 04:29 PM

Be sure the alternator to starter accessory harness is good. It is separate from the engine harness of great notariety.

mbsteve · #10 07-12-2004, 09:33 PM

Steve

Where should I be looking for this harness? The alternator is tucked away pretty good. Do I need to remove the under carraige panel and look from underneath or can I see what I need to from above?

Thanks

Steve