2013 GLK350 4Matic 330,000 KM

Alternator and battery failed Dec 23 2024 in cold weather (-20 C, ~ -4F)
Found battery had a bad cell, and alternator regulator wasn't working properly (forget what it exactly was).
Voltage/current status display showed low voltage and negative current. Red battery indicator was displayed.
Replaced alternator and battery. Alternator is a locally rebuilt alternator from a trusted vendor in Ottawa ON.

A few days ago in cold weather (approx. -12 C / 21F), the red battery indicator was displayed. Brought car home, used my charger/analyser to charge battery in car, charged ok. Showed 90% capacity (cold weather, I guess), but fully charged. Started car and used voltage/current status display, showed 12.4 volts with a negative current value.

Waited a few days, weather warmed close to freezing, and poof, no more problems. Changing display showed battery charging up, finished at 15 volts with about 1.5 Amp positive current value. Worked great.

This morning, was -12 again. Used the voltage display again. Was charging up normally, the engine began surging and display showed 12.4 volts and a -35 Amp discharge value. Red battery indicator finally appeared. Got to my local garage (10 KM / 6 miles away) and discussed, set up appointment. Left for home (5 minutes away) and voltage/current display was normal, 14.4 volts and climbing, 4.5 Amp charging current.

Looks like a temperature related fault. I'm thinking that the engine heat warmed something up under the hood a few degrees and charging started again on the way home. Any ideas what might be failing? Maybe the sensors on the battery cable? Maybe a poor connection somewhere? Battery connections seem tight, can't get at alternator.

It's certainly a mystery, and I dont want to go very far with this happening when the temperature changes up and down. It doesn't seem that cold when it fails, but it definitely seems temp related.

Many thanks for your thoughts on this weird issue.

 

Locally rebuilt alternator ? So nothing was probably done. The regulators are what fail on the alternator. Get someone else to scan it , auto stores do it free . I would think it’s the “rebuilt “ alternator. Can you get your old one back ?

 

My mb regulator failed at 80000m , they are known to fail . I will bet the regulator is shot, temperature changes make it apparent, FCP euro has lifetime warranty and regulators for about 100$. But I think you should just get a new alternator with a lifetime warranty from FCP. The problem with just a replacement regulator is the Commutator is still worn, that should be replaced or the brushes might not seat properly.

 

A year or two ago i was having the red battery warning pop up as i was leaving my driveway after the first start of the day. When i got to the end of the street I would turn the car off and restart it and it was fine afterwards. i bought the Ancel BM200 wireless battery monitor and hooked it to the battery so i can see the voltage in real time. I know the car shows it but the battery monitor shows everything on a graph and can see it even with the car off and im in the house. It works with bluetooth and a phone app. With it i was able to see the voltage jumped as i started the car which indicated the alternator was fine and charging.






The warning stopped coming on so I didnt really need to fix anything. Have you scanned the car with a Mercedes specific obd scanner? That may tell you if theres any issues with the bsm or alternator either stored or current.

Have you inspected the belt, idler pulley and belt tensioner to rule those out? On mine I was thinking maybe there was condensation on the belt and causing it to slip first thing in the morning and fixed itself when warmed up. No idea if thats true or not.

 

What do the colored boxes on the graph signify?

I doubt moisture on the belt would cause anything significant.

 

My interpretation in Reply ... "voltage jumped as i started"

 

Once 25 years ago my very qualified mechanic put on a rebuilt Starter on our Cadillac , in a month 7 of his Quality Rebuilt starters failed. 7 that’s SEVEN failed . Stupid putting on a old junk alternator, Fcp euro life time guarantee

 

In Canada, FCP Euro is not a viable option. Their prices are extremely high and they charge exorbitant shipping rates to Canada. You then add in $1.38 per dollar exchange rate. Do you get an advertising fee for your constant pushing of their products?

 

I spent months communicating with them regarding shipping to my U.S. address. Nothing but the run-around, getting handed-off to other people, etc. I've certainly read that there are people that are happy with their service but I think they're far from deserving endless promotion.

In my book they're useless - based on my personal experience.

 

Well, any update @KanataSteve ??
Might be good feedback for others with similar issue.

 

I got new struts from fcp, I hit a curb and bent one , I shipped it back and got another one back no questions asked. I don’t know any other company that would do that . Then i bought fluids I never used , I got cash back. That’s a good reason they are worth dealing with . No I’m not paid or support them . I just was treated well with cash back.

 

Wrong thread again.
P.S. Ooops. Sorry, the second last sentence is relevant.

 

No, it’s not. That was a response to post #8.

 

It has gotten warmer here for the last few days. As the temp increased above -10°C, I have had no further problems. Currently, it is +2°C, roads and sidewalks have fully melted (just in time for 20 cm of snow coming today). Charging is working like a champ. Looks like a teardown project in the spring. I'm betting on a loose connection within a connector (e.g. a pin or lug not crimped tightly).

Charging ok

 

Thanks for the feedback ... it must be a challenge dealing with the extreme cold environment as yours.

I have seen odd behavior with batteries and charging, even in our area (it was almost 80*F in south Texas a couple of days ago, now down to 50*F)
My experience, even down here, when a battery is reaching its age limit, odd behavior happens.

I always use a trickle charger on all our vehicles every now and then (cars, zero turn, etc), which also shows its integrity.

 

Yup, I'm with ya C-C. Been there before too. Curiously though, my battery is 12.5 months old and has tested good on my analyzer- even in -15°. I did test it while connected to the car though. Hmmm. Maybe a good thing to test while disconnected. I think though, that I will take it back to Canadian Tire for a test as well. I wonder if a little jiggling and tapping around on the bench while being tested will highlight a damaged cell that only fails below about -12°C.

 

Missed seeing TimC300's post earlier. Looks like the battery voltage graphed on his battery monitor jumps back up during the recharge cycle and then reduces to the original nominal value. The internal display on my car goes up to 15 V and stays there with a minimal ~1.5 A charge current after the recharge cycle has completed. Anyone know if that is normal?

 

Hmmm. 12 1/2 months old ... should be fine, but ya never know.

I recently replaced the battery in our 2014 GLK350 Base.
If I remember correctly, the original battery lasted ten years!!
( I bragged about it in another battery posting )

I was going to buy another MB-branded battery from the local MB dealership.
However, I bought a top-quality generic from Wally-World. (I think it has a five-year warranty at 1/2 the price).

As far as "jiggling the battery". I'm not so sure that applies to these sealed gel batteries.

And yea, for peace of mind, a quick trip to Canadian Tire for a quick test would be a good idea - shouldn't take long to do.


Personally, I've never paid attention to the voltage output on the dash, thought that might a good idea.
I actually keep the "tire pressure" display on all the time, because I'm paranoid of a leaky tire

I will occasionally do a "battery load test" on all the vehicles around here.
I use a tester bought from Harbor Freight .... I know some folks will laugh.
However, that tester that's 18 dollars USD has been accurate for years !!
(CEN-TECH 100 Amp, 6/12V Battery Load Tester)

Let us know what Canadian Tire thinks ...

 

Yeah! The "toaster tester". Had mine for at least 15 years.

 

My original battery was M-B, it finally died after abiut 10 years. I bought an M-B replacement which failed just slightly after the 1 year warranty. They wouldn't help. Sheesh. Even after paying $700 for something that crapped the bed so early. So, since I was calling them (M-B) from the Canadian Tire parking lot, I bought one there at C-T. C-T was quick and easy, with a 5 year warranty on an 800 Amp glass mat. We'll see what they say on a test.

That load tester sounds pretty good. Unfortunately, sending stuff (e.g. from Harbour Freight or whoever) to Canada gets kinda crazy price wise, due to shipping, duties, taxes, and also these newly added reciprocal tariffs lately (taxes, if you want to speak in layman's language). Sounds like you get a good deal there, even after paying U.S. import duties and taxes at the starting end of the import process from China.

I'll let you know what C-T finds.

 

those type and look of battery load testers can be found worldwide, under various brand names, for not much money. they're very simple/basic and they work.


i know nothing about this seller. legit? who knows?

https://www.ultimatetooldepot.com/pr...y-load-tester/

 

That exact load tester is on "sale" for $36.00 CAD here at Canadian Tire. Sheesh!

 

I'll take two at 5.40 USD each. Then I have the option to use both at the same time to do a heavier load test of 200 amps :-)

okay, I won't actually do that but it's a good option if you can actually get them that cheap.

 

Yea, I bought the new battery from Wally World (Walmart) back in Mar of 2025, so almost a year now.
I paid almost $260 USD for it ... it has a five-year warranty.

Even if it gets weak in another year, Wally will replace it, no hassle.

Here's the battery thread from about a year ago (testing and replacemtn)

https://mbworld.org/forums/glk-class...load-test.html

 

Order 6 and get free world wide shipping.

Most (all?) of those items carry Harbor Freight labels.

Sometimes when a deal looks too good to be true, it is.