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Car is not charging - Swapped alternator and no dice. Prefuse Possibly?
Guys, I'm scratching my head on this one.
Alternator is kaput - ran down the battery 100 mi north of LA. Towed back to Orange County. Swapped in a new Bosch reman alternator .... unfortunately the car is still not charging.
I checked the prefuse under the passenger front footwell --- all three "fuses" show continuity. Is it possible that the prefuse is still bad though? I found this thread where someone had my SAME symptoms and issues ---- and this person swapped the prefuse (even though he had continuity across all three "fuses") and it FIXED the problem!
OP Check voltage at the alternator output lead on the back of the alternator as it runs. 14 volts there? If so a connection is missing between there and the rest of the car.
12 Volts when running? Verify the alternator is getting the signal from the car to excite the field and charge (small wire to alternator... In the days of old this one would be red in color.)
You don't mention a warning in the cluster about charging. Continuity tests of fuses very often don't tell the tale. Digital 'logic testers' will lie. A TEST LIGHT with ground on one end and an incandescent light bulb (think the bulb used for interior lamp in cars from the 1970s) that has a pointy end to probe things with will tell you if you have power on both sides of a fuse. Light on one side of fuse and none on the other... It is junk.
'Reman' alternators come out of the box may look nice and are JUNK. It happens.
Thank you. I will test alternator output of the old alternator and new reman alternator and see what I find.
I will also take apart the prefuse again and see what I can find. Question - to replace the entire prefuse (if that is the issue) do I need to access the underside of the car?
You don't mention a warning in the cluster about charging. Continuity tests of fuses very often don't tell the tale. Digital 'logic testers' will lie.
GO FISH friend.
By the way, John, very perceptive, you are right. I did not mention a warning in the cluster about charging. I did not have such a warning. The only warning I had was a red warning about battery low. That’s it. Everything was fine one minute, supposedly, and then battery low voltage warning.
I read through your post four times and I don’t understand the significance of not having a “no charging warning message”?
Thank you —- I’m a bit slower in understanding these days. 😀
'06 MB S55 AMG; '04 Audi Allroad 4.2; '05 BMW M3 Conv.; '92 MB 500E
I think the Battery icon on the dash IS the no charging warning, but I could be wrong. I've only seen that once, and that one time, the alternator was no longer charging the battery.
It has been long enough ago that I got to do the alternator in the 221 S-65 that I don't recall if there is a separate warning for low battery and charge voltage. I always set the cluster to display volts and oil temperature (? failing memory).
Radiator got to come out to pull it in that car..... Alternator failed.... few months later A/C compressor failed.... Then the radiator failed. Was a treat.
I had the 20 year old original alternator tested at Autozone --- 13.8V! Is this good or bad or borderline bad? Autozone says its good but looking at w220.wiki seems to infer that 13.8V is kinda the cutoff point. Wondering if this would have really caused my car to run down its battery. Note the 0.86A reverse current -- not sure how to interpret that.
Bosch Rebuild #1 that I swapped in was BAD!!! Yikes!
Bosch Rebuild #2 --- I had tested before swapping it in and it looks healthy at 14.6V with much less reverse current. Again, not sure how to interpret.
I haven't started up the car yet. I'm still waiting for a new PREFUSE to arrive to swap that in too. 🙏. Praying.
I replaced the alternator with Bosch Reman Alternator #2 and all is good - the car is charging again. Amazing to me that the old alternator at 13.8V wasn't working right and the new alternator at 14.6V works well. 13.8V would have been considered perfectly fine for most other cars.
I did fuss with the prefuse box. Notice that the previous owner did a bodge repair job and left out a bolt at the top right .... but I THINK that bolt would be the connection to the starter, and hence not affect charging.... right? Regardless, I replaced the voltage smoothing capacitor and the BIG 150A fuse from the top. I did not replace the 60A fuse or the small 150A fuse from the top because I couldn't figure out how to extract it from the top.
Are you using a O.E.M. alternator because I had a similar issue before with after market alternator turns out I tested with amp meter and it was .5 amps less then the factory one enough to cause voltage drop and make it stall out totally
Are you using a O.E.M. alternator because I had a similar issue before with after market alternator turns out I tested with amp meter and it was .5 amps less then the factory one enough to cause voltage drop and make it stall out totally
My pictures show that I am using Bosch Remanufactured alternators.
Bosch remains are as good as it gets short of being abused by Mercedes; who has them rebuilt as well.
Intermittently we encounter one that doesn’t work out of the box or that fails a month later.
It happens.
The crappy remans come from the corner parts store who offers a $200.00 rebuilt alternator. Decades ago that was the only available choice and one would get to replace it 2-3 times before finding one that worked.
You'll be alright that's why I'm always looking for parts the dealer isn't carrying parts for anything older then 2008
They can order parts that are not stocked. Depending on where you are they arrive a day to a week later if stocked in the warehouse. If they come from Germany you’ll be waiting a while.
They said no my local dealer no parts for any vehicle older then 2008 yes I'll be waiting a while for remanufactured parts from Germany or other European nations but at least i know they work
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