2004 420 sport

[vorpefactorx]

I have a 2004 420 sport with Volvo TAMD diesels. 75% of the time when I start the Port engine my battery / alternator warning light / alarm goes off. The gauge is reading correct voltage and a mechanic put a meter on it an it showed correct voltage. I changed the alternator out as a precaution and same thing. Any clues or thoughts?

[Viper]

Do you have a hard time turning the engine over or does it turn over normally? Do a proper load test on all batteries. Also a test with an electronic battery tester will tell you right away if there is a bad cell that might be causing an issue with the charging system. Check all battery cable connections including at the starter. Make sure the connections are clean, tight, and free of corrosion. If there is an issue turning the engine over, also do a voltage drop test while cranking the engine, simply checking voltage at a static state doesn't tell you much if the trouble occurs while starting. Also check all control connections and plug pins including the engine harness plug at the engine and the instrument panel. Look for a charging and a main system circuit breaker on the engine. Corroded internal contacts can cause all kinds of funny symptoms.

I don't have a schematic in front of me but if you provide a spec or serial number in the next day or so, I will see if anything stands out. A serial number would help narrow down the exact build.

[vorpefactorx]

The engine starts and runs fine. It is a ghost problem as the alarm goes off only about 75% of the time. Seams to do it more at low RPM right after I first start it up, the alarm "sometimes" shuts up later in the day. So it can be a battery?

[Viper]

I wouldn't discount the battery but the symptoms are pretty common with a poor connection somewhere.