Odd Electrical Problem

[Rob95]

My 2000 C280 Sport is showing some strange electrical problems.
When driving at night with a significant load on the electrical system (Rear defroster on, fog lights) and either my radar detector or cell phone plugged into the cigarette lighter I experiance what I can only describe as a brown out or reduction of power. The lights will dim and either the 2 Yellow BAS lights on the left of the instrument cluster or the two other red indicators will light up and the car will sputter. If I remove the item in the cigarette lighter all returns to normal. This also happened to me when I turned the high beams on for an instant. (No Cigarette Lighter)
Once I turned the highs off the problem went away.
Could this be an alternator or computer issue. My wife complained about this during the day also when she had the blower fan to max with the radar detector plugged in. The detector read low voltage and the dashboard BAS light illuminated. Once she removed the detector all was normal.
I would like to know if anyone has seen a similar problem and where should I look?

TIA

Rob

[benzaddict]

Rob,

If the power draw comes in without things plugged into the cig lighter, in other words you can eliminate that socket from the source of the problem, I would check your battery and alternator output. If your ABS/BAS/SRS lights are coming on it's obviously due to low voltage, they are the most sensitive to low voltage due to the fact that they are safety systems. I can think of 3 things to check:

-Check your battery cables for corrosion or loose contacts
-Test your battery and see if it is weak due to a bad cell or low acid/water level.
-Do an alternator test, if your alternator is worn it won't be able to keep up with the power consumption.

Please be careful when checking your battery and wear face protection!! I know this sounds silly but 202's have a history of batteries exploding (there was even a recall). We've had several blow just in our shop and battery acid all over you is not fun.

Good luck...

[jnolte]

i am having somewhat of the same problem. I am thinking my alternator may be going but am not sure yet. It could have something to do with my sound system also. So i am getting a new battery and seeing if it solves my problems, if not alternator it is. my battery however has been weak from the start and i should of replaced it a year ago!

[Rob95]

Benzaddict, Thanks for the reply. Ill check the battery. should I have the Alternator tested at a shop or is there a way to do it at home?
Also, after thinking about the car I had a recent problem with the blower fan where it would work intermittently. Eventually it quit altogether until I hit a big NY City pot hole and it came back on for a min. The problem was a corroded supply wire to the motor wich I replaced. That got it working but now the fan speed is quite irregular at times. so much so it seem to have its own mind. Could the regulator for the fan motor be causing a problem with the electrical system?

Thanks

PS the Car has 221,000 miles on 2nd altenator (Replaced @ 160K by MB)

Rob.

[benzaddict]

You can check the the alternator output voltage at home if you have a volt meter, with the car just off idle it should be somewhere around 13.3-14v at the battery posts. You probably don't have a large enough ammeter at home or a load source so you might want to go to a shop to have it tested for amp output.

Sounds like you have a blower regulator issue as well, might try to replace that first and see if your issue goes away, since you already know that's a problem. A blower reg can pull quite a load, but I don't know that it would pull so much that it would make warning lights flash. Maybe in winter with the rear defrost, headlights, wipers, radio, etc. all running as well it could. Either way, a basic charging system test is cheap (or free) at most shops.

[Rob95]

Thanks for your reply again. I will check it out at the shop and replace the fan regulator. Its a problem and it wont fix itself.


Thanks Rob