No it was late when he did the alternator swap, the battery light was off when the car started and everything seemed like it was good to go

Two possibles for the motor noise ,air cleaner ,motor mounts.

The stock air cleaner was ripped out by the previous owner, and the motor mounts are new. It's a rattling sound, it rattles in 2 second intervals every 5 seconds at idle, and gets much louder and a little bit more frequent as I rev the engine. It sounds like it's coming from the bottom pass side of the engine

Late not good excuse. Takes 30 seconds to check. Shame on Colin. Battery light off does not guaranty good charging voltage.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Do you have a battery drain? Try to measure it with a amp meter. Or disconnect the battery every time you turn off the car. See whether it will restart again.

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Hmm, maybe I didn't tighten the pulley bolt down when I switched them over. Try that first.

This noise wasnt their before the alternator change? The replacement alternator is a good used unit right. Im going to guess the noise is something in the alternator making the noise ,A washer or screw has found its way into the unit,If it sat around on a bench or a parts ben this could be a very possible scenerio .It also could be its bearing going out.You could take it up to a parts store to have it bench tested while also hearing for this noise to make itself known.If good but only noisey take it apart to see if something is in its cage. If not its likely a bearing issue

I can see the alternator fan moving out of place when I hear the noise, I'm going to check it out when I put the little one down for a nap. I also spun the fan while the engine was off and it would get stuck and have a lot of resistance about halfway through the turn.

Also, my gp light has been coming on at random, as well as when I get on the throttle, it's possible that I have a bad gp relay and that the alternator does in fact work, but the battery is being drained by the gp's coming on. However since my gauges are on the fritz that could also be preventing the battery from charging.

A bench test is in order, and there's a car quest about a block away from my apartment, I could take the alternator out and walk over there and have them test it. If it's good, and the voltage regulators good then that leaves my gp relay and the gauges. It's a pain in the ass but it is all pretty simple stuff.

Well I pulled out the alternator and there was no nut for the pulley, so that thing managed to unscrew itself and come off, although the pulley is still in tact, which explains the rattling. It tested fine, and I figured out the source of all my trouble (I hope), a loose ground strap, the chassis to bellhousing ground. I tightened that up, put the alternator back in and I'm in business, the car started right up with the starter, I just gotta get that nut but I'll do that in the morning, Lowes is w/in walking distance.

So I'll see if my gauges are good, the fuel gauge was close to E which may or may not be true, but my gp light came on as it was supposed to and turned off as it was supposed to; and my tach read what it was supposed to read.

Thanks Colin, and everyone else in the forum! You guys rock! And Colin, there is a good possibility that my old alternator and regulator still work so you may wanna check that out.

Yeah I think I put that pulley on and didn't tighten the nut down very hard because I wasn't planning on using that pulley, but didn't want to lose it. If you can't find it at Lowes feel free to swing by and I can give you the one off of your old one.

I'll test the alternator, but still at least we ruled that out completely.

Did this fix the starter issue too?

The starter is working now, so I guess it was just a bad ground that was causing the starter to work intermittently, and the alternator to not charge the car. I drove this evening and at startup everything worked as it was supposed to. Gp light turns on and stays lit for 10-15 secs, then the car started right up, but while driving I noticed the gp light came on why revved around 3k rpm and at the same time the tach started acting finicky. My fuel gauge may or may not be reading accurately but I have to wait til Tues before I can do a fill up. The needle is right above 1/4 tank, judging by what I've put it in that sounds about right. But while driving I had the fan going, the wipers, and the lights. 2 nights ago that was enough of a load to drain my battery completely, but I was able to make 4 short trips within a 2 hr time frame and when I got home there were no signs of a low battery,

I'm going to pull the cluster out tomorrow and clean all of the contacts and check the grounds, and add the extra ground like in the write up, hopefully this will solve the gauge issue, and maybe I can get my clock to work too. If that doesn't fix the gp issue then I'll switch the relay, and after that, I'm startin a new thread lol.

I think I'll swing by tomorrow to get that nut so that way I don't have to try to guess which size nut to buy. I'll shoot you a text and let you know what time.

I had a loose ground strap when I first got my first W123 Mercedes and it caused a lot of weird problems in the cluster lights in addition to not starting. As I recall, it damaged some traces in the cluster. Do a search with my screen name and stranded, there may be info in my thread that may help you.

ps, get the pulley too in case the pulley got damaged with no nut on it.

__________________
85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

http://www.peachparts.com/shopforum/diesel-discussion/277167-w123-300d-fuel-tank-sender-question.html

http://www.peachparts.com/shopforum/tech-help/190632-fuel-gauge-sending-unit-threads.html

http://www.peachparts.com/shopforum/diesel-discussion/71819-fuel-tank-light.html

http://www.peachparts.com/shopforum/diesel-discussion/189366-fuel-sender-85-300d-cleaned-pics.html


**********************************************


Algae/Fungus fixation...
Algae/Fungus fixation... - PeachParts Mercedes ShopForum

Biobor, what is it, why do I need it???
Biobor, what is it, why do I need it??? - PeachParts Mercedes ShopForum

Filters, Fungus, Biocide, etc.
Filters, Fungus, Biocide, etc. - PeachParts Mercedes ShopForum

Algae Clogged Filter Pic StarTron WORKS !
Algae Clogged Filter Pic StarTron WORKS ! - PeachParts Mercedes ShopForum

300SD Fuel Filter Replacement Instructions
300SD Fuel Filter Replacement Instructions - PeachParts Mercedes ShopForum

240D fuel tank removal and cleaning
Good for any W123 sedan.
240D fuel tank removal and cleaning - PeachParts Mercedes ShopForum

Check out this fuel pickup screen
Check out this fuel pickup screen - PeachParts Mercedes ShopForum

W123 Fuel Tank Screen Replacement
W123 Fuel Tank Screen Replacement - PeachParts Mercedes ShopForum


.