04 C240 Alternator?
Last night went to jump in the ol' 240 and started really hard (took a lot of turning over and seemed to be losing power). Thought it was strange but took off anyway. Drove it a couple miles and shut it off for maybe 5 minutes and it wouldn't start. Had it jumped and drove home.

I started researching on here about battery drains from the CANBUS, seat module, blown fuses, etc. Basically made me frustrated and I called it quits till I could have the battery and alternator tested today hoping it was the battery that was still under warranty. I was getting 12.10-12.2 V when I stopped messing with it. I had similar issues on another vehicle in the past when it lost a cell and had only 30% of the CCA.

Tried to start the car this morning and it almost turned over. Was reading 11.99-12.1 V. Jumped it, took the long way to the auto parts store without any lights, radio, or fan on and started the test.

Battery test was good, recommended recharge as it was only at about 500 of the supposed 720 CCA. Next the alternator test that required the car to be on so I got in and viola it started like normal. Did the test and it can back that the alternator was bad. During idle it was at 13.8 V, but under load it dropped to somewhere around 13.2-5 from what I understand which the guy said means the alternator is bad and not keeping up when all the accessories were on. Not that I don't trust him, but I plan to have it tested at a different store to confirm. I like to make sure the equipment that looks like its been beat off the sidewalk actually works since the readings were close to passing (store guy said 13.6 V was minimum).

So that's the story and I wanted to see if any one had any thoughts, maybe how I could test the alternator my self, or recommend what I should/could do to ensure that is actually the problem before I go to the hassle of ordering an alternator. I've changed a couple alternators in my life and its not that difficult, plus it looks like I can get an OEM Bosch for about $120. It may be good maintenance to change it, but I don't want to spend that and still have the problem.

Just looking for some thoughts, I plan to spend some time looking into the alternator install later today. Thanks for the help.

 

Another avenue of failure is the belt. The days of the V belt and tension adjusted by swinging the alternator farther from the crank are over. A multi rib belt is now used and follows a serpentine path to drive all rotating components. The tension is set by a spring. The spring wears out, and the bearings in the tensioner and idler wear out too. It is possible that when the alternator is producing current the belt is slipping on the alternator pulley.

You could also have simply bad regulator brushes. The replacement assembly is about $50. There are two OEM suppliers. Make sure you actually have a Bosch alternator, and using the free online EPC input your VIN to make sure your car was supplied with a Bosch alternator.

Anytime your voltage readings are slightly low, you need to examine battery and ground strap connections carefully. They should be shiny and tight.

 

I'll be looking into those tonight. Figured I'd try a different store and if I get the same result, I'll start digging deeper (checking belt, pulleys, tensioner, connections, etc.) before I decide to pull the alternator. Been doing a lot of looking and seem to come across those items as potential culprits. As a note I'm also not getting any of the warning indicators for the battery/alternator.

Even then I hope to be able to find a place that can bench test just the alternator. I've been down the road once where I replaced the alternator because the store associate was sure it was faulty, only to find out it was something else.

For the regulator brushes, are you talking about the voltage regulator?

Since I'm that far I may just go ahead and replace the tensioner/pulleys to make sure they're good to go.

I know it just maintenance and parts fail, but I was hoping after spending that last couple weeks getting my vehicles in line I wouldn't be doing much of anything for at least a few months. But I guess that's how it goes.

 

How many miles are on the car? Depending on miles, a worn out alternator seems likely. Before you start, I would test the alternator rather than have a parts-shop do it. Testing an alternator is easy, and (since you did the work yourself) you can trust the results. Here is how you do it:

1. Grab your favorite Multimeter. Mine cost $5 at the local discount tool shop.
2. Use your multimeter to check the voltage (at the battery) with the car off.
3. Use your multimeter to check the voltage (at the battery) with the car on.
4. The voltage with the car off should be ~12.5v, and with the car on, the voltage should be higher, normally around 13.2v.

If the voltage with the car on is higher than the voltage with the car off, then chances are the alternator is OK. From there, I would check a few other things to find the problem:

1. Check to see if your getting a good connection between the battery terminals and the battery. Do this by confirming the bolts are tight on the terminals, then use a multimeter to run two tests:
2. Check to make sure you don't have a drain.
   • Make sure your car is off, with every light, accessory, etc. also turned off.
   • Disconnect the negative battery terminal from the battery post
   • Set your multimeter to 'Amps'
   • Put the multimeter probes between the battery terminal and the battery post.
   • You should see a very minimal draw. Investigate further if you see over 1/2 amp.

Now that you know the results, its time to take action: My assumption is that your alternator is not putting out any voltage. If this is the case, its time for a new alternator.

While replacing the brushes may fix the problem for the short-term, chances are your in need for a replacement alternator.

I have tried replacing the alternator brushes (as mentioned above), with poor results. My two experiences included 1) there wear on the rotor shaft causing excessive wear to the brushes (new brushes failed within 50 miles), and 2) the bearings in the alternator were worn, causing the alternator to wear out again within 6 months.

We have the OEM replacement alternator in stock: Bosch Alternator from Oscaro.

Hope you get it fixed quick! Let me know if you need any other help.

 

Thanks Garret.

I have 95,000 miles on the odometer. If it's the alternator, I planned on replacing the whole thing anyways.

What you described was going to be my "digging deeper" approach.

I'm pretty sure I don't have a drain. I've had that experience in the past with another vehicle and the battery would be dead over night. No lights, no radio, no windows, no anything the next day. Not such the case here as it nearly turned over when I went to start it on the second day to take it to be tested and as far as I can tell it still has some charge. Lights, radio, windows, locks all work. Still plan to check it, but I'm not sure its at the top of the culprits list.

 

So test results

1. Car off 12.05v (multimeter) 12.4 (onboard diagnostics)
2. Post voltage, terminal voltage, and remote posts all have same voltage ( within 0.01V)
3. Car on 13.30V at start (multimeter and onboard)
4. Car on with fan, lights, high beam, and radio at idle 12.66V but falling over time (multimeter) bottoms out around 12.2
5. Car on with all the above at 2500-3500 rpm little change in volts, 12.60V
6. Car on but no accessories, starts at 13.3V but falls to 12.33V within a minute and keeps dropping but seems to bottom out around 12.2V. It still drops but about .05-.1V every 20-30 seconds at that point.
7. Holding the rpms at 2500 the voltage doesn't change on the multimeter or the onboard diagnostics

After checking the voltage through multiple scenarios the voltage never increased while the car was running.

I'm guessing that indicates there is no recharging from the alternator. That's isolates my problem. Guess ill pull it this weekend and have it independently tested before I order a new one.

Just forces me to spend some time behind the wheel of my first car love or on one of the bikes (human or gas powered).

 

Make sure to stick with whatever brand alternator you take off you don't want to deal with what in went through a few weeks ago.

 

I haven't had a chance to pull it out yet but I found some rebuilt Bosch alternators that are decently priced. Through some researching I saw some posts where someone would by a Bosch and it would have valeo stamps on it. Somewhere I read that they were interchangeable.

Either way it is listed as an OEM alternator that had been rebuilt.

What problems did you have?

 

You can easily distinguish between Valeo/Bosh IMHO.
Just look at the pictures of both, and compare to what is installed in your car

 

So finally got the alternator out. It's a Bosch 150A. Not that I would put in the generic reman from the local national auto store, that is if they had it. They couldn't even bench test it since they don't have a 150A that would fit the car so no way to program the machine. I found a reman 150A Bosch on rock auto for about $150 with no core charge. Comes with a lifetime warranty for what's its worth. It's rebuilt by TYC but only other option is a Beck/Arnley that's $30 more and wont ship right away with a $50 core charge. Not sure what it would cost or even where I could take it locally to get rebuilt so TYC it is.

 

I think there should be no problem with reman Bosch alts. Especially if they give a lifetime warranty.
It's not very pleasant to R&R it though, but at least you would not have to spend more money if it were to fail.