Date registered: Jun 2009
Vehicle: R129 500 SL 1991
Location: South West, UK
Mentioned: 0 Post(s)
Quoted: 279 Post(s)
How many miles? What is the rpm at idle, and also just before it shuts off?
Battery light will automatically come on if revs drop too low to the point where the engine is about to stall, or when engine has stalled but ignition is still on.
If your OVP is more than 5 years old I would replace it anyway.
You can check the ignition switch by measuring voltage across the fuse box terminals (in the engine compartment) and earth with a multimeter. If one or more are showing lower voltage compared to others, itís usually a sign that there is a problem with the ignition switch, which incidentally is relatively common to early CIS-e V8s.
Although sometimes a faulty ignition switch causes a drop in amperage, not voltage, which is harder to measure.
A faulty ignition switch usually starts out intermittently with either one or a combination of the following symptoms - engine randomly cuts out, random non start, flashing instrument cluster lights, random cluster light outage.