kraabel

After a wonderful summer last year of driving the MY90 around, I thought I had everything figured out. This spring, after driving her for about a week, something funny started to come up, but it's not all the time.

I was sitting in my driveway the other day making sure everything was working. Checking lights I noticed that when the lights were on and I clicked on the high-beams that the car would stall out. I assume it's a short someplace.

Anyone have any suggestions on where to start?

Lizard928

pull the headlight relay and try again.

This will eliminate it being from the relay to the combo switch.

And if the car will not start without the relay then you have some wiring to do.

dr bob

Make sure the battery is charged well. Verify charging voltage at the jump-start terminal in front. It should be greater than 13.5 at idle. I've not seen any that actually make the 14V regulator rating. A deep dip in voltage there as you turn the headlights on can indicate a weak battery or alternator. Try the headlight test again with the engine at 2000 RPM's and see if that helps.

Stupid stuff: Make sure the alternator belt is tensioned adequately. A belt that isn't tight enough will slip and you won't know it by listening. Firm thumb pressure should deflect the belt about half its thickness; That's a lot tighter than many people believe a belt should be, but that's usually what it takes. At full rate,the alternator belt is trying to transfer about three horsepower from the crankshaft, and that driven pulley is pretty small.

Lizard928

Actually Bob, both of my stock S4s produce 14.04V at idle

That is with all accessories off (ie no headlights)

dr bob

Mine doesn't. ;( 13.8 at the jump post or battery, that's at idle with nothing extra running, though. Might make it to 14 at higher RPM's.