Haywire Voltage !

[metal slinger]

I was driving around last night when suddenly my radio went off and then came back on. There also was a noticeable thud in the motor. So I looked down at my scan gauge and noticed that my voltage was fluctuating from 12 volts to 14.8. I had the defroster on (ac) so I shut that off. I then turned the ac back on and again noticed that all my lights dimmed right out and the radio turned off and then on again (not enough juice, no problem with radio or wiring). Here is the deal.......ac off the voltage fluctuates as above....... when you turn the ac on the whole electrical system bogs down and then comes back to normal as if the ac was off until the ac kicks back on again. I also noticed that I had to unplug my scan gauge with the key in the off position as it was lighting up with funny colors. This is not a normal operation and is telling me that something is backfeeding through the OBDII plug.
All electrical connections are clean and dry and tight so is this a alternator or pcm problem I don't know.

[Lou]

Problem with the compressor shaft? -- seized, sticking ?

How's your belt?

[metal slinger]

Compressor shaft is fine. I did some rooting around and on a hunch put in a blue top Optima battery. All is well now. The original battery was only six months old but was not taking a charge very well (internal short-high resistance?). So even though this thing would start fine and all, it was sagging out at times when the ac would kick on (revs drop, alternator output drops,aux fan spikes the battery) which was putting enough of a hurting on the pcm to falter the whole system momentarly. This is also what was causing the battery voltage to go all over the place because there was not enough reserve left in the battery to handle sudden high amp draws.
I put in a Optima D-34m and on another hunch checked the voltage before putting a charge to it. 12.7 volts I checked my other battery right when I took it out and it was 12.3 volts. At 11.8 volts you are considered eighty percent discharged. So there was the problem. Put the old battery in my truck, the truck has no issues with it.\

On another note....I ran the Optima down to 11.5 volts and then started the Jeep for twenty minutes. Let it sit for ten and then checked the voltage..12.7
There is that low internal resistance for you. I would have had to charge the other battery for a good hour and a half to get the same effect only for it to fart out in no time flat.