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This in on an 07 Cls550 w219 with 100k. No traffic in the 219 section & w211 are very similar.
Prior to changing the alternator, I had no charging issues or battery lights. It was replaced with a 180amp reman unit from Car Quest as preventive maintenance. I was changing the water pump & figured while I was in there, might as well change it.
Installed the new one and now I'm getting a red battery light 5 secs after startup. If I clear it, it stays off the entire drive until I start it again.
Icarsoft code reader shows - output for the actuation of the alternator has a malfunction.
Battery shows 12.5v, when starting it drops to 11.3 for 3-5 seconds then goes back up to 13.5 / 14. 5v while charging & driving. All seems normal. I had the battery & charging system tested at autozone, they said everything looks brand new, can't remember the exact #'so but said it look perfect.
The only thing I noticed was it appeared to take the alternator a few seconds to kick in & start charging.
I'm thinking a bad /slow / out of spec voltage regulator but wanted to see what everyone else thought.
This in on an 07 Cls550 w219 with 100k. No traffic in the 219 section & w211 are very similar.
Prior to changing the alternator, I had no charging issues or battery lights. It was replaced with a 180amp reman unit from Car Quest as preventive maintenance. I was changing the water pump & figured while I was in there, might as well change it.
Installed the new one and now I'm getting a red battery light 5 secs after startup. If I clear it, it stays off the entire drive until I start it again.
Icarsoft code reader shows - output for the actuation of the alternator has a malfunction.
Battery shows 12.5v, when starting it drops to 11.3 for 3-5 seconds then goes back up to 13.5 / 14. 5v while charging & driving. All seems normal. I had the battery & charging system tested at autozone, they said everything looks brand new, can't remember the exact #'so but said it look perfect.
The only thing I noticed was it appeared to take the alternator a few seconds to kick in & start charging.
I'm thinking a bad /slow / out of spec voltage regulator but wanted to see what everyone else thought.
Agreed. Retail alternators are junk; try rock auto, OEM, or Euro Parts dealer. I've had good experiences with TYCs, WAI is 'okay' though I can't stress OEM enough. Denso and Bosch do it right; won't touch Remy, BBB industries or ANYTHING remanufactured. Autozone, AAP, NAPA, EBAY and Amazon unless it's OEM alternator I will not touch it. Too many failures in a year or less on those - sounds like yours is exciting slow. Good luck
What symptoms are pointing to a bad alternator? Just curious since it was load tested & passed.
Took it for a ride last night with the scanner hooked up. 1st photo was during start up & idle hence the low 11.63v 2nd & 3rd are while running.
It does seem odd that it takes a few seconds before it starts charging & I see the voltage jump to 13.5 - 14.5. But then again I never paid attention to it before.
Edit.
I drove the car for about 30 mins yesterday. Alternator volt output was always 13.5+, parked the car overnight. Before starting it today I checked the batt voltage & it's only showing 11.8v.
Could I possibly have a short in the batt or is everyone still saying bad alternator?
Last edited by Ken Keith; Mar 26, 2025 at 08:46 PM.
Ken, It shouldn't have dropped into the 11's. I have a Jaguar that was doing the exact same thing your alternator is now doing. Replaced it 2 weeks ago and no issues.
Like the avatar pic...
Agreed. Retail alternators are junk; try rock auto, OEM, or Euro Parts dealer. I've had good experiences with TYCs, WAI is 'okay' though I can't stress OEM enough. Denso and Bosch do it right; won't touch Remy, BBB industries or ANYTHING remanufactured. Autozone, AAP, NAPA, EBAY and Amazon unless it's OEM alternator I will not touch it. Too many failures in a year or less on those - sounds like yours is exciting slow. Good luck
TYC and Wai Global are OK with me. The Bosch/Napa remans are absolute garbage for me
Ken, It shouldn't have dropped into the 11's. I have a Jaguar that was doing the exact same thing your alternator is now doing. Replaced it 2 weeks ago and no issues.
Like the avatar pic...
The 11.8 was with the car off & directly from the battery 24hrs after driving it. I agree it shouldn't be that low and why I'm hesitant to blame the alternator since it appears to be putting out the proper amount of voltage & has a decent wave pattern.
I was hoping someone could point to specific data showing the alt is faulty and not the battery.
Appreciate the comment. It's one car I miss & regret selling. Especially for what I sold it for, 13k. It was a 93, bought it for 10k with 80k back in 2002.
Appreciate the comment. It's one car I miss & regret selling. Especially for what I sold it for, 13k. It was a 93, bought it for 10k with 80k back in 2002.
I still have mine, sitting in the garage haven't driven it in 10 years. I started it up about 6 months ago, ran fine!
TYC and Wai Global are OK with me. The Bosch/Napa remans are absolute garbage for me
Remans period. I don't even warranty them at this point.
Also OP, I've had a known bad alternator pass with flying colors on a bench load tester. 2004? Maxima 3.5, was a reman unit, I even told the customer it may dump out in under a year. 6 months later, guess who was ripping it out. Bad excitement and would only charge over 25-2600rpm generally. Bench test showed no issues - had to argue with the guy.
Load testing the battery won't hurt. They normally sit around 12.3, but you've got an obvious drop there. Cheers man
Last edited by BBBAAUTO; Mar 28, 2025 at 02:38 AM.
I still have mine, sitting in the garage haven't driven it in 10 years. I started it up about 6 months ago, ran fine!
Nice! Love those cars. Can't believe you don't drive it more often. Tracking down a tiny vacuum leaks in a 100 ft of rubber vaccum tube is the worst. Have you had to rebuild the motor/apex seals yet?
I might have to check the auction sites & see what these are going for these days.
Alright, I think I got it figured out. Made a few trips the last 2 days & haven't seen the light, come on.
The 1 signal wire going to the alt kinda loose, I cleaned & tightened that connection & also cleaned the battery terminals, which I believe was the issue. . There wasn't any visible green/white corrosion on the terminals but they did have a sticky funk on them. Cleaned & tightened the terminals & haven't seen the battery light since.
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