merc_if

Hey guys. I am having an electrical issue on my car.

All the lights and console work fine on battery. But after I start the car all the lights including the instrument lights start flickering. Do you guys have any idea why??

I have checked all the fuses and battery for connectivity issues. Was't able to find any.

My first thought was the ignition system. Is there anything to replace except fro the Coils and spark plug wires (which I am planning on doing)?

Also, what is this part? Looks like part of the ignition system. Its making a ticking noise as well.



Thanks.

Critter

Your voltage regulator or the alternator itself is the issue. Could be diode related( internal to the alternator), have you open sparked a 12Volt system lately, or possibly boosted a car or your car and caused a large spark connecting the terminals.

merc_if

Thanks for the reply.
I haven't had any sparks or boosted anybody. Also, the battery seems to be charging fine.
I will check into voltage regulator replacement.

Is there anyway to test the voltage regulator and the alternator?

Critter

Can you measure the voltage with the car off (battery voltage) and then with the car started. You should see 12.6-12.8V battery only and then 14.1-14.2V car running. Alternator makes AC power and the rectifier/diode package turns this to DC so I believe yours is an internal alternator issue, but just saying is this the original alt and what is the mileage on the unit.


Meter across the battery terminals will work for both tests.

merc_if

Just tested.

With engine turned off: 12.8V steady
With engine running: fluctuating between 14.2V - 14.5V

I couldn't find anything in the service history about replacing the Alternator, so I'm guessing it is the original, so its got a 100k miles on it

Critter

Yes, the only issue is that the 14.5V seems a bit hot, can you retest and see if the 14.5V raises when the car is revved to say 1200rpm. Thinking probably a voltage reg may solve your problem.
14.1 -14.2 with minor fluctuations between those values is good.
Can you retest with increased rpm

merc_if

Here are the values at different RPMs:
1000rpm: 14.3V - 14.5V
1200rpm: 14.7V - 15.2V
1500rpm: 14.7V - 15.2V
2000rpm: 14.9V - 15.4V

Critter

Voltage regulator is no good, when you get upwards of 15V you will start to effect the electronics in the car and could cause damage, sorry will cause damage. Change it out soon if not right away, any continuous driving will boil the battery out

Critter

With a good Bosch regulator and stay with a "Bosch" unit your voltage will not climb up past 14.2 and remain steady thru all rpm ranges at the 14.2V.

merc_if

Thanks bro. Nice catch as I am planning to drive it 3000 miles across country in a weeks time

Hopefully it will be an easy replacement. I am ordering one now!!!!!

Will let you know how it goes

Critter

Wonderful, yes that trip would have had some stories when you got back, "when you got back".
Another small point if the bank account permits possible look into a new unit as at 100K miles you are on borrowed time as far as bearings go, your choice but for sure the reg.
Happy holidays.


Since you will most likely have the serpentine belt off, check it and any idler pulleys for looseness spin them with your finger if they spin for a long time, get out the wallet and splurge. You want the 3k trip to leave a smile on your face. Enough said starting to feel like Dr Phil

merc_if

Ha ha.

True that. Will be doing as much as possible within the next week. A new alternator is definitely on the books

Fatz

Just a note on similar issue. Over the past several weeks I noticed these intermittent issues;
- Radar detector power lost (unit is hardwired)
- On starting the car within an hour or 2 of driving it would turn over 2-3 times longer than usual before starting
- I would hear a single beep sometimes when driving
- Dome light sometimes would not come on after starting the car until after several seconds of idle
- The engine would sometimes seem to "skip a beat" at stop lights.

I checked the battery voltage with the engine off and it was about 12.7V; about 14.5 with the engine running.

The battery is the original (so it's about 7.5 years of age)

I had the battery checked at Advance Auto and the was deficient on cranking power. With that bit of validation and the age of the battery I replaced it with their "Platinum" battery. I did note that the new battery is rated at 95 cranking amps vs. 100 for the original. I think I can live with that.

It has only been a few days but the startup cranking is normal, no more beeps, no radar detector going off in the middle of being adolescent, and the cabin lighting comes on immediately.

The engine "missed beat" has not been noticed, but that may not be related to the battery anyway.

This is just info to the masses............

Critter

You have had good service from your OEM battery at 7.5 years it has passed its useful life for sure.
Wish owners of other Benzs could read your post as it would assist them also when it is time to replace a tired battery. Even though you have the 12.7 the battery was running low amperage output.
Load test is the best way to test for sure, but at 7.5 it would already have been changed out in my car, I go 5 years max.