mustang_kicker

hey guys i just have a quick question concerning my electrical system. The car is running normal and all and when i drive it for a bit everything is normal, reads 14 volts on the guage, but once i start turning on too many things it seems like the alternator just stops working. Usually it can handle the lights, heat and radio, but once i turn on the rear defrost the guage drops to 12 and wont go back up, even if i turn everything off. If i stop the car and leave it set for a few hours it will work again. I just replaced the battery, and 2 shops checked the alternator, they both said it was fine. But thats the only component that could be not working properly as far as i can tell. Any thoughts ?

texFCturboII

iTrader: (17)

Check the connections to the alternator, is it only when you turn on the defroster? If it is I would check the connections there too.

Azn_Boi

iTrader: (1)

I wouldn't 100% trust the shop for alternator bench test. My alternator passed 2 different shop's test and in the end it was bad alternator It's better if u find someone u know that u can use their alternator for a test. See if same thing happens, if it does then it's not ur alternator - if not then it could be your alternator.

ericgrau

iTrader: (1)

Intermittent problem. Make your alt fail, then have them test it on your car, not pulled. Or wait until the problem becomes permanent. Or just replace it anyway (assuming you don't need to prove it's bad for a warranty claim).

mustang_kicker

well i have checked all the connections and they are all hooked up tight. I think Ill replace the alternator and hope that works then, i dont think i could get any other alternator in there to test.

texFCturboII

iTrader: (17)

+1.... just get a new one

crazyasu

This is one of the very few gauges which you have the option of going analog or digital. Very few people run aftermarket voltmeters in their FC's; the non-turbo FC's already have voltmeters stock in the instrument cluster. It's surprising to see how much the voltage fluctuates while driving.

During driving, the voltage should be at least 12.5VDC. It'll be nicer if it's over 13.0VDC at around 13.5VDC or higher. Do not let the voltage get over 15.0VDC, as this will cause potential problems with electrical components and blow the battery up due to overcharging.

ericgrau

iTrader: (1)

The voltage is supposed to be 14-14.5V when driving. It's ok if it temporarily reaches 12.5-13.5V at idle while under heavy load. That just means that the car is relying on the battery. But if it's relying on the battery most of the time, that means the alternator is getting old. Might still be usable, but it's weaker and may eventually fail. My first '7 had an alt like that for a very long time. Wasn't much of a problem until I put the e-fan in, then every once in a while it wouldn't crank and I'd have to use a jump box. That's the way an alt should blow, btw; slowly after a long long time when the $4 brushes finally give (or maybe the bearings). All these alts blowing all of the sudden shows what lousy rectifiers and voltage regulators they use - or I should say re-use - in remans. Those, OTOH, are $40-$50 new, and I'm sure they won't replace both if they don't absolutely have to. Wouldn't be surprised if they found a cheaper substitute for them too.