rx7speed

just wondering if you guys can give a hand here

the car has a fairly new 100 amp alt but it seems most of them test around 120-130 or so.
the battery is brand new

when I bought the battery (old one was 11 years old) put it in noticed I was having the same issue as I Was before. low voltage readings especially for the larger alt. had him test the batt in the car when the car wasn't running
took the battery back in and he grabbed another one and tested it right there before I put it in the car and it came up good
put it in the car started up same thing voltage around the 13.5 range and easily drops when load is put on the system
well had him come out to my car and it showed unstable voltage again with the car turned off.

I have noticed that when just sitting there car off, ignition off, everything off the voltage will jump around by around .1volts or so sometimes up to a peak of .2v

but it isn't constant flicker just a flicker every now adn then

any ideas as to what can cause the voltage to flick around like that as I assume that might be part of my charging voltage issue?

Trickster

What are you using to check the voltage when you have the car sitting there with the ignition and everything else turned off? Have you had the alternator tested? And are you sure it isn't just the meter that you are using that isn't causing the flicker?

rx7speed

the meter that was checking my car was one of those meters they use at the parts stores.

and by unstable voltage I'm not refering to the meter jumping around..... the meter actually displayed "unstable battery voltage"
but when testing the battery before even putting it in the car it tested good.
though I have taken it home and used my dmm and it does seem to flicker around .05-.1v or so while sometimes hitting a whole .2v flicker.

as far as the alt I tested it about 3 months ago or so and it was good 14.6 volts no load 14.2 or 14.3 under load.
but with the car off the alternator shouldn't be an issue right?

firebirdjosh

iTrader: (1)

.2V flicker is nothing. Most meters aren't going to be accurate enough to consistantly show a .05V difference just by holding the probes to the battery. If it isn't broken...

rx7speed

but any idea why the tester the guy uses at the car poarts store willl say "unstable voltage"

xlwhellraiser

iTrader: (1)

Ya, thats the same problem I am having, however its only under heavy load. I am talking all the accesories and heat and everything. It will drop even under 13 when I have everything on. However, its all good when am running some of them. It like, when I run some of them the voltage would be pretty stable at time, but sometimes it will drop down to 13 and raise up.