Pulsing headlights and dashlights on 98 V70?

[dripcandles]

Its been around 20 balmy degrees here in upstate NY. When I first start out driving at night my electrical system has a pulsing. The headlights and dash lights dim, as well as the heater fan slows too. This happens every 5 seconds for 1 second, and repeats. I thought maybe it was the A/C compressor cycling because defrost was on, but it still happens with the defrost off. Any ideas?

[Ozark Lee]

The first place I would look is the battery cables. All of them at both ends.

...Lee

[greasefingerss]

My head lights dim for a second every time the air pump is energized. This is probably due to either the motor pulling too many amps at start-up (bearings probably dry?) or an electrical wire/connection is compromised for this circuit.

Your problem seems to be different as the dashboards lights are also dimming.

Cleaning the battery posts and terminals is an excellent place to start, as Lee suggested.

[JRL]

As was said a good place to start are the battery cables, these DO fail and now after 10 years, many are becoming corroded and fraying apart

[dripcandles]

Thanks for the suggestions. I will check the cables, although they looked clean as can be the last time I looked at them. I had the intake off last year to do the pcv replacement and the cable to the starter didnt look bad. I will check the ground. I did think it could be the air pump because the electric dims in a very cyclical way, 5 seconds then 1 second dimmed, then repeats. I would have suspected water in the air pump froze up and prevented it from turning, but I did the vw air pump swap and when I did I drilled the drains holes, so I dont think that would be the case, but I will have to get under there and look around. I wouldn't know where to begin in chasing a bad circuit, other than check the connectors.