voltage going crazy

19mustang65 · Oct 11, 2004

it all started today when i winned out my engine at about 110mph, i had my lights on and as soon as i starting winning and backed down to 70 my volt gauge started bouncing back and forth like crazy between 11 and 14. as soon as i turned my lights off it went back to its normal 13.5 or so. i turned the lights back on and the needle drops to 11 then back up to like 12.5 for about 2 seconds then starts bouncing again. any suggestions on this?

reenmachine · Oct 11, 2004

Drive with your lights off.

Just kidding. Do you drive like that often, or is that a rare occurance? Just wondering if the problem cropping up just then was a coincidence or directly related to spinning the engine up. Check your alternator for proper operation, and check out the voltage regulator as well -- I've seen them cause some pretty bizarre problems.

Is it directly from activating the lights, or just from increased electrical load? Power up the stereo or wipers or something and see what the gauge does.

19mustang65 · Oct 11, 2004

thats the first time ive gone that fast..ive had it up there about 100 so not to far different. it only jumps with my lights... nothing else does it. it has a new voltage reg.

19mustang65 · Oct 11, 2004

i just replaced my alternator and it continues to do the same thing. doesnt seem to hurt anything. it doesnt do it with the running lights... just with headlights. maybe short somwhere?

19mustang65 · Oct 12, 2004

well i just got home from work. its about 1115 pm here. on the way home i got pulled over by a cop because my headlights where flashing on and off. they just happened to be doing it with the beat of the volt needle. hmmmm im guessing i have a short somewhere in my headlights

rbohm · Oct 12, 2004

check your ignition switch, and headlight switch. the ignition switch is likely the cause here. i had the same problem with my old F250 once.

WORTH · Oct 12, 2004

the headlight switch has a circuit breaker built into it, it more than likely has a short in the headlight circuit and the breaker is turning the lights on and off. unplug the bulbs first and see if the short is still there, then trace out the wireing.

19mustang65 · Oct 12, 2004

i unplugged the bulbs and its back to normal. no jumping or anything. circuit breaker?

WORTH · Oct 12, 2004

19mustang65 said:
i unplugged the bulbs and its back to normal. no jumping or anything. circuit breaker?

Yes if you buy a new switch it should be capable of halogen lights, I had to replace mine in the 70 ragtop because the old one couldnt handle the halogens.

19mustang65 · Oct 12, 2004

i do have halogen lights so maybe thats my prob...wheres a good cheap plce to get a switch? pep boys or somthing or do i need to order it from sombody?

19mustang65 · Oct 12, 2004

i unplugged one light and left on in and the volts drop but they dont jump and the headlight doesnt flash.

91conv · Oct 12, 2004

I had the same problem. Was using Halogen bulbs with the stock set-up. I switched back to the stock lights and all is well.

19mustang65 · Oct 13, 2004

i installed a new headlight switch. the volt guage doesnt seem to jump yet with both headlights on but it does drop down to about 12volts at idle..when i drive it raises up. now the volts rise when give it gas and drop when i let off while lights are on.. maybe it is the alt?

19mustang65 · Oct 13, 2004

or maybe my battery is going bad?

jaredgoodwin · Oct 13, 2004

Relays...

Just get some relays for your headlights. That way you can run better headlights than stock. Does your voltage drop to 12 at idle (w/headlights on) and go to 14 when you step on the gas? If it does, your alternator does not put out enough current at idle. This is not really a problem as the alternator will catch up while you are driving. I rewired my headlights with new wires and relays, upgraded to H4 bulbs, my headlights are 10x better now. Before I rewired them (just had the higher wattage bulbs), they started doing the flash on and off thing. After I put in the relays they worked perfect.

19mustang65 · Oct 13, 2004

ok, im gonna go to an auto parts store today, like napa or auto zone. should i just ask them for 2 relays? any kind works?

WORTH · Oct 13, 2004

19mustang65 said:
ok, im gonna go to an auto parts store today, like napa or auto zone. should i just ask them for 2 relays? any kind works?

You shouldn't need the relay setup with the new switch, and low charge at idle is not a problem unless you spend all day idling.

You fixed it with the switch.

notny41 · Oct 13, 2004

Glad the policeman pulled you over for headlights flashing and not for going 110!

19mustang65 · Oct 14, 2004

yeah no kiddin, that would have been real bad

ashford · Oct 14, 2004

check the engine to chassis ground or batt to chassis ground, a weak connection there will drop voltage all over that have body grounds , while the alt and battery see little drop

voltage going crazy

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