Quote:
Originally Posted by Diseasel300
The OVP relay can be a source of problems as suggested above. They're not expensive to replace and are a VERY common failure item that will affect several parts of the car. If the car really is idling down around 500-550 RPM, it can cause low alternator output. The normal idle speed when in gear should be somewhere around 650 RPM.
If you want to diagnose low voltage, get a cheap voltmeter that plugs into the cigarette lighter and watch the voltage as you sit. If it heads down and keeps going, you have a charging system problem of some sort. At idle with everything in the car on, you should be 13V+ if the charging system is working correctly.
How old is your battery? Occasionally an old battery can misrepresent an alternator issue.
Has anyone checked the engine ground strap to the chassis and the chassis connection to the battery? Poor contact can trick the alternator into thinking that it is producing adequate voltage due to low load conditions caused by poor cable connections.
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Hi Diseasel, thanks for the input. As I just posted, I made a silly mistake not to include the fact that the dealer sourced an OVP from Mercedes Benz Classic in California to trial fit on the vehicle. They ended up experiencing no change in symptoms.
As for my idle speed, the tach needle usually stays stable just above the 500RPM mark. To me, it looks more like around 600RPM, but I could be wrong. If it helps, here's a picture of the tach around 10 seconds before I begin to experience those symptoms.
As for the cigarette lighter voltmeter, that seems like a very good thing to try (especially because it's so cheap!) When I get a change I will give that a shot.
As for my battery, I am 99% sure it's not to blame. I bought it in December of 2016 (it was actually dated January 2017) so the battery had not been sitting in a store for any time whatsoever. I dropped it off at the batteries plus I purchased it from for them to do a 24 hour test. The results came back stating that the battery was in excellent condition and actually producing 100 more CCA than intended.
The engine ground strap to the chassis and chassis connection to the battery are things over my head. I haven't heard anything about them at all, neither from the dealer or from the garage. I will definitely bring this question up to both of them the next time I am in contact with them.
Do you think I am on the wrong track with replacing the alternator with a higher amperage one?
ALSO - the garage revealed to me today that the alternator they have installed on the car is not actually a 70A, but an 80A one. I wasn't aware of this at all - probably should have took my phone camera down there to try and see the model number of the alternator they installed!
Again, I really appreciate your effort in helping me solve this strange problem!
Winston