Volt gauge jumping low when lights are on.

[dustin_8907]

Exactly as it states. Am I needing a new alternator? It jumps pretty low and irratic when the lights are on to the point that I'm scared to drive at night

Thanks for the help!

 

[undefined0000]

Specific numbers would help a 'lil, but yeah, sounds like its time for a new alt.

 

[dustin_8907]

Specific numbers would help a 'lil, but yeah, sounds like its time for a new alt.

Sorry . It varies a lot. Sometimes down to 8 or 10 but it always pops back up to around 14

 

[casperfast]

a volt meter on your battery will tell you if the alternator is dead or if one of the diodes is gone, should be at least 12.8 min when idling. if you dont have one, turn the lights on, if you give it some throttle the lights should get brighter indicating the alternator is doing something. might even be the battery is going out. u want at least 12.5 with the engine off. 12.3-12.4 can mean the battery is weak and going out.

 

[dustin_8907]

a volt meter on your battery will tell you if the alternator is dead or if one of the diodes is gone, should be at least 12.8 min when idling. if you dont have one, turn the lights on, if you give it some throttle the lights should get brighter indicating the alternator is doing something. might even be the battery is going out. u want at least 12.5 with the engine off. 12.3-12.4 can mean the battery is weak and going out.

Okay thanks!

 

[undefined0000]

Well 12.6 is technically full charge on the battery with the car off. anything less than 12 isn't charging. 10 will barely keep everything going. At 3k rpms you should see from 13.5-14.5 Anything less than 12.6 or higher than 15 would indicate malfunction.

 

[dustin_8907]

Well 12.6 is technically full charge on the battery with the car off. anything less than 12 isn't charging. 10 will barely keep everything going. At 3k rpms you should see from 13.5-14.5 Anything less than 12.6 or higher than 15 would indicate malfunction.

Hmmm.. So do you think my cause of so low of readings could be caused by a poor ground from the alt.?

 

[undefined0000]

Haven't really heard of anything like that, the ground is like hard to not have right. Is it only low at idle? Like mentioned earlier, you battery could be junk too. Take the car to your favorite auto parts store and have them load test your battery and alt. I go once every few thousand miles because the test is free and just lets me know how my electrical system is going. Ever since I lost my first alt in the middle of no-where, I'm kinda anal about it.

 

[dustin_8907]

Haven't really heard of anything like that, the ground is like hard to not have right. Is it only low at idle? Like mentioned earlier, you battery could be junk too. Take the car to your favorite auto parts store and have them load test your battery and alt. I go once every few thousand miles because the test is free and just lets me know how my electrical system is going. Ever since I lost my first alt in the middle of no-where, I'm kinda anal about it.

Okay yeah I'll do that today. It's at idle but it jumps from 14 to 10 back and forth real fast. Never seen it happen before. Lol. I'm kinda scared

 

[casperfast]

i would want to verifye that voltage jumping with a meter on your batt posts. that sounds like a potentially twitchy gauge. real fast switching is not a typical symptom of battery or alternator failure. the alternator ground is almost impossilbe to not have right since it is grounded through its mounting. like undefined stated, most auto parts stores will test it for you for free. but keep in mind the numbers we have told you and pay attention when they test it. they only do it for free so they can make a potential sale, and some employees are told to say all batteries or alternaotrs are bad regaurdless of the test result. if the load test is done it must be set the YOUR batteries specific cca (cold cranking amps) or the test could show a failure, just be careful. like most things free there is often a catch.

oh and one more thing, things like batteries and alternators usually die in pairs since one is working so hard to make up for what the other isnt doing. so dont be surprised if you have a bad alternaotr then all of a sudden your battery goes tits up. they should usually be replaced togather.

 

[undefined0000]

Ugh casper, you are so right. I had my first car, 92 Cadillac deville and I was getting them to load test it to check and it showed a nice 14 volts. I could barely understand this guy to begin with, sounded like he was talking with marbles in his mouth and he said my voltage regulator was bad... wtf.

i would want to verifye that voltage jumping with a meter on your batt posts. that sounds like a potentially twitchy gauge. real fast switching is not a typical symptom of battery or alternator failure. the alternator ground is almost impossilbe to not have right since it is grounded through its mounting. like undefined stated, most auto parts stores will test it for you for free. but keep in mind the numbers we have told you and pay attention when they test it. they only do it for free so they can make a potential sale, and some employees are told to say all batteries or alternaotrs are bad regaurdless of the test result. if the load test is done it must be set the YOUR batteries specific cca (cold cranking amps) or the test could show a failure, just be careful. like most things free there is often a catch.

oh and one more thing, things like batteries and alternators usually die in pairs since one is working so hard to make up for what the other isnt doing. so dont be surprised if you have a bad alternaotr then all of a sudden your battery goes tits up. they should usually be replaced togather.

If the alt is bad and you REALLY can't afford a new battery immediately, just make sure you charge it when the new alt is put in/overnight. A dead battery will kill an alt pretty fast, literally burns it up.

 

[casperfast]

i hear ya, just think of them is a slighty more qualified gas station attendant. but that being said, i did work at an auto parts store full time while attending college, but i also worked at flowmaster as a welder at the same time part time (at 19 years old ) so they arent ALL dip$hits. on the other hand, i do believe a 92 caddy does have a regulator separate from the alternator. ours are internally regulated

 

[undefined0000]

Very true. Some of the guys there have some nice project-looking cars, its just the dumb ones are really dumb . I think it might have been an external regulator too, its just that it was supplying good charge and he still said it was bad.

 

[casperfast]

the dumb ones are really dumb . .

thats awesome. perfect. makes me think " my names forest, forest gump"