mithious

So the idle in my "new" 93' sol drops when I turn on the lights. I haven't noticed it dropping with any other electrical devices, and in writing this just now I realize I should test that. (but I don't think it does)

Google is my friend. And I happen to have a multimeter. So:

First I tested the alternator.
-battery with engine off: 12.5
-battery with engine on: 14.4
-battery with engine, lights, rear defrost: 14.2

So the alternator is fine right? No significant drop. Under 14 and I would have been suspicious.

So I'm thinking ground... All I know to test so far is the engine ground.
-connect lead to positive on battery, negative on engine block with engine off: 12.5
-same with engine running, 14.3 to 14.4

I'm no electrician but that seems to be grounded well.

What's next?

grumblemarc

iTrader: (4)

Nothing. Sounds normal.

mithious

Thanks for the reply. I actually hadn't considered that.

crazyhouse2011

Think about it this way, hoss. When you turn on the lights you are putting a momentary large current draw on your alternator, which in turn increases the resistance of the pulley, and slows your engine down. Mine does it too, with an all original 150k mile alternator in need of eventual replacement. The only reason why i still have it is on a dry day with lights on and heater at max, rear defrost, im putting out 14.0 volts, and battery is always above 12.4 volts when dormant.

mithious

Thanks, it makes sense. If I was a bit less of an airhead I would have realized I've had cars with this before... It's just a log less noticeable on my '97 civic than my '93 sol, and I had gotten used to the civic.

Nobody has ever called me hoss before. For some reason that made my day.

stupidhard

how many rpm does it decrease? possible ELD issue? does it create a drivability issue? my rpms drop pretty low when the brake lights illuminate, cant tell how low cause I have no tach. sorry not tryin to jack the thread.

grumblemarc

iTrader: (4)

His case is normal. ELD issues throw CELs. Start your own thread.

stupidhard

easy marc... I DID say I wasn't tryin to lift the thread.

guess I gotta keep my mouth shut