I sometimes get a rough idle when the lights are on. I hope its not a coil breaking down. Anyone knows how to check the coils via the multimeter.

Anyone recommend an affordable code scanner from ebay etc?

 

A ton of folks have had good results going to Autozone to get a code read-albeit it is usually when there is actually a warning light on.

Not sure what year your SC is...but if you are under warranty take it in.

Typically (in my car experience) when loads are put on the charging system this happens when the charging system is not at 100% Do your RPM's dip down then come up a little higher? Does it happen with the a/c as well? Not sure what year your SC is, and we haven't heard of too many alternator issues YET on this forum but around the 8-10 year mark alternators can go for the first time. My 95 SC300 back in 2001 had a premature failure of the alternator which I only found out after replacing with an expensive Optima battery. It had RPM and idle issues when a load was put on the car and even eventually stalled after I installed the new battery too-so that's when I knew it was something more than just the battery. Do you have any starting/igniting issues or hesitation issues?

 

Unfortunately, I live across the pond in Australia. We don't have a Autozone, pepboys where they can scan your car - hence the hand held scanner question.

The idle is dead set at 600rpm, and about 800rpm with the aircon on. I'll put the multimeter on the battery and see what the alternator is charging at. No there is no starting or stalling issues yet.

An alternator rebuild is not too expensive as I can get this done whilst the timing belt is being done.

PS : mine is a 2002 model with 140,000km on the clock, revs smoothly to redline - no hesitation issues.

 

Idle should be at 750 +/- 50 rpms without the air and 800 with. The generator should be putting out between 13.2 and 14.8V at the voltage regulator. Battery voltage should be between 12.5 and 12.9 at 20 degrees C or 68 degrees F.

 

I think the 750+/- 50rpm idle would be when the car is in park or neutral. When my car is in drive the revs is 600rpm.

 

Seems like your jump is a little extreme, as you mentioned in your first post. Just curious...with no a/c on and you turn on lights or several things (try wipers, stereo and put down a window) what do the rpm's do?

 

Thanks, I'll check this out this weekend.