well, was out playing in the snow tonight and noticed i have a little electrical quirk. when i put my signal on, headlights dim, when i use power windows headlights dim.. voltage pegs at approx 13 whist driving with no radio, heater, rear defogger etc running.. if i turn on the heater goes down to a hair above 12. is my alternator crapping out, or is it something else?? thanks....

A little voltage drop when accessories are turned on is normal. But your headlights shouldn't dim when your turn signals and stuff are on. your alt may be taking a crap. You can have it tested at autozone. but it may just be a loose/corroded grond somewhere. sheck your negative battery cable top begin with. then check the body and engine grounds.

One simple test you could do yourself. Put your multimeter at Volt AC and connect the positive lead to the Alt output and the other one to ground. If you get more than .5 volt AC it's a sure sign the alt rectifier (diodes) is failing. It's often the diodes that fail first (I think) in an alternator.

But consider that if this test is OK it does'nt mean the rest of the alt is OK.

Just one easy test you can do.

as Caleb says, check all bat cables for signs of the greenies

clean as required.

Frag has a nice tip too, it should be checked

but

Another common place for voltage dropping corrosion is the main fusible link. (These are in the little black box on the overflow bottle, The "link" is a wire shaped like an upside down "U"with a spade connector on each end ) The one closest to the strut tower (rear most) is the alternater output to the battery and car circuits. The male to female spade connections like to corrode and drop voltage. If they do, the connection then gets hot (current through any resistance creates heat) This heat can take the "springyness" out of the female spade and cause even more problems.

 

Look for the greenies though, they could be out to get you.

Hope this helps

I'm definitely gonna have to check my fusible link for corrosion. Thanks Skip!

 

What about an old battery?

thanks guys... will do...