Thread: Bad Invertor dont fry my computer!

Hi, Ive tried looking at old posts to see if I can answer my own question but I cannot: The problem is well ive got two power invertors and multiple blown fuses.

Heres the senario:
Im running a P2 233 in an atx case with a 250watt power supply (i have a power button wired up front). My car is a Jeep Cherokee and has a cigarette lighter slot and an extra power adapter.

The first invertor I had I got from BGmicro for like 35 bucks and well it worked for a couple days, at first it was plugged into the power adapter but then i moved it to be plugged into the cig adapter due to its proximity to my seat. As far as i know I sometimes turned the engine on with it plugged in and turned on and not, im not positive but i think it experienced various states of being turned on. Anyway a couple of days ago it didnt turn on, and i found out there was a fuse in the dc connector that had blown, thus i went to radio shack

Now the people at radio shack are real good, so this guy found a fuse and even put it in the invertor and tried it out in the store (it worked but i realized later that it had no load on it). So I jubilently went to my car and plugged the computer back in and watched the fuse blow out in seconds. I tried another fuse in the power adapter, same thing. The guy at radio shack suggested it might be my car. (its brand new practically)

I thought that maybe a transistor was blown on the 150 watt power supply so i milked out some money for a Tripp Lite 140 watt power supply, well, it came today much to my reluctance.

Instantly i hooked it up and powered the car on. I flipped the on switch and noticed that the on switch was kind of blinking, i thought, well maybe its supposed to, then i heard a crackling which i though to be radio noise, but i looked back in my trunk and saw my power supply sparking, quickly i did the normal thing and scrambled to turn off the engine. I was really stumped now. Why didnt the fuse blow on this supply and what the hell woulda cause the power supply to start frying? BEsides this invertor is 10 watts lower than the previous one and i havent changed the computer at all.
Ok so i did one final test, I brought a basic alarm clock into the car and plugged it into the invertor, first i tried the invertor in the power adapter with the engine off--it worked, i turned the invertor off and on and it was fine, then with the engine, still fine, then i switched to the cig port and it was still ok, then i turned it off and back on, and finally the fuse decided to blow. Bummer. Now Im confused.
Can anyone sort through this mass of info and come up with any ideas as to whats wrong, I would greatly appreciate it.