How to fix

[namdray]

Hello. I have 91 Corolla and some type of electrical problem. Symptoms: Headlights flash when apply brakes, dome light will dim in rhythm with haz flashers, radio goes off/on when apply brakes or turn signals, etc. Hoping for advice maybe voltage regulator, alternator, battery, or what? Thanks in advance.

[Createdtoburn]

Heh, first, start your car and use a multimeter to check the voltage you alternator is putting out. It should be atleast 13.5, but if its healthy it should be like 14-14.4 volts. Now if its below 13 you should look into getting a new alternator.

If your alternator checks out ok, check the voltage on your battery with the car off, it should be at atleast 12 volts. Do you ever have problems starting? And even if the voltage is good, it could be an old battery and the amperage could still be low and whether or not you charge the battery or not. To check the amperage you could use a good battery tester, or go to your local autoparts store, some places will check them for free. Atleast around here.

And by the way, the voltage regulator is usually built into alternators these days, some older older cars had their voltage regulators seperate from the alternator, I remember my 86 Mustang V6 did.

But yeah it mainly just sounds like a typical low voltage problem. That kind of thing is very common when you have a nice sound system in your car (with subwoofers usually) and the amps draw too much current from the battery. Goodluck.

[REN69]

Easy test too... with your car running, take the positive cable off the battery, if the car shuts off then your alternator is toast, if it keeps running then it's fine so its most likely your battery that's not keeping the charge properly.

I recently had my Protege die on me with similar symptoms... turned out it was both battery and alternator.

[Axxis8203]

alternator

[namdray]

Much thanks for the helpful suggestions. Will report back results!!