Hey all,

So I have a 1990 240 DL and the lights are all fluctuating, including the headlights and it's quite a problem for me. I have already put in a brand new voltage regulator on the alternator and I am stumped as to what the problem could be. Reving the engine does not solve the fluctuating but does lessen it. The battery is less than a year old.

 

Check the tension on the alt belts. Check the voltage across the battery with the engine running. Does it bounce around? Could be the battery cables need cleaning up.

 

I wold check your grounds and look for corroded wires.

 

Voltage on the battery with the car off is 12.70 volts. Voltage with the car running on the battery is around 14.4 volts, and it seems pretty constant. I cleaned the positve and negitive battery terminals and hookups today with little result, I will clean the alternator connections tomorrow and try that.

 

Yes, from the symptoms, I would've guessed voltage regulator too. Is this a Motorola alternator or Denso?

 

Sure sounds like alt brushes or voltage regulator. When my brushes were going the voltage would bounce around. Finally just died.

 

It's a mystery for me too. The voltage regulator is a Bosche, brand new. It did nothing when I replaced it, so perhaps the brushes are the problem. How much is it for a new alternator or a rebuild of it?

 

You have ~14v with all the lights on? And all the lights fluctuate, including the tail lights? Do you have a 8000W sub-woofer in the back?

The negitive (blue) battery terminal should connect to the frame/body in 2 places - clean those connections.
Clean all the fuses in the fuse panel.
Remove the round (red) bulb failure relay under the dash, above the driver's feet and clean the pins.

 

I thought brushes came with a new VR. They did with mine.

http://www.fcpgroton.com/product-exe...ategory_id/112

 

Oh yes the regulator came with new brushes, i never realized that's what they looked like. The amplifier for the subwoofer is only 300w RMS. I will clean the negitive terminals today on the battery. I get ~14v on the battery with the subwoofer going full blast and the lights. And the lights always fluctuate even when the gas is applied, it only lessens.

 

No offense but if I had known you put in a 300-watt whatever onto an 80-watt alt I would have watched from the sidelines.

 

LOL ... At least it wasn't a 8000W whatever. I need to post a picture of the thumpin' stock AM radio installed in mine. With the two 4" door speakers.

 

The problem is there whether EVERYTHING is off including the amp or OR everything is all on. It never stops. So the amp is irrelevent! I checked the grounds on the battery and cleaned + sanded all the contacts onto the engine and body with no results. I am quite confused by this problem still and any help is apreciated. The alternator is more than 80 watts, my headlights alone would be 65

 

I would go to the junkyard and try another regulator. No use spending good money on a new one for this test.

 

Dude, I mesured it today - my AM raido THUMPS with .000002 AMPS