1998 S90 Electrical question

anbran1 · Post by **anbran1** » 17 Mar 2015, 14:59

For some strange reason, after starting my car, the headlights, dashlights, blower, etc. rhythmically dim slightly every 3 seconds. I'm not sure if it continues while I'm driving....(I don't notice it anyway...)

Any ideas?

Its been a very cold winter and the battery has performed very well...So I don't think it's that.

Alternator on the way out? (It can be noisy sometimes)

1998 S90 514,000km (319,000 miles)

lummert · Post by **lummert** » 17 Mar 2015, 15:26

It's easy enough to check the alternator output with a DMM. I don't know if your S90 uses the same relays as my 1988 760, but I had strange electrical issues caused by a main relay that is rectangular in shape and about the size of two standard relays. I dug around in my parts stash and found one from a 92 960.

anbran1 · Post by **anbran1** » 21 Mar 2015, 20:53

On closer observation, I notice the engine drops in rpm slightly at the same time as the dimming...