Blowing tail light /parking light fuse

I have searched on this subject and have found some answers, but not the exact problem I'm having.

 

I have a 1999 Legacy Postal wagon. The other day, my wife noticed I didnt have any tail lights. Checked the fuse and it was blown. Replaced it and it instantly blew again. Changed all the bulbs (every exterior bulb.) Put a new fuse in, and it blew again.

 

Tore apart the back and found a corroded ground wire and a little cut in the tail light harness. Repaired both, put a new fuse in, and problem solved...for a day.

 

Going to work this morning, and when I backed into my parking spot, I noticed no taillights. So, went home, tore apart the back hatch, and all the panels out. Looked for any broken wire or anything, and it all looked fine.

 

I put a new fuse in, turned off every load in the car...no heat, no AC, no headlights....just the parking lights. Sat for about 30 minutes, idling and fast idling....lights stayed on, fuse was fine. The second I put it in drive, the fuse blows. Turn on all loads (radio, AC, interior lights. Headlamps...everything...changed the fuse and it was perfect...idled low and high for 30 minutes...put it in drive and POP goes the fuse. What am I missing? This is my daily driver, as I work for the post office.

Update: for some reason, my dash lights just stopped working too. Fuse for them is not blown. Weird thing is, both that fuse and the taillight/parking light fuse are good, but I still dont have parking or tails....

 

 

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Update: fixed the interior light issue...one of the fuses wasnt pushed in fully.

 

I also noticed that the voltage was running around 12.5 volts today, and everytime I stepped on the brake, it would dip to around 11.8-12.2 volts. If I turned on any loads, it would dip below 12 volts. So, I figured there was a grounding issue, so I changed all of the battery cables and added a couple more grounds (from engine to battery, from battery to chassis and from chassis to engine.)

 

Voltage now seems to be at 13.4-13.6 idling, and with all the loads, it dips to 12.8-13.2. However, when I put it in reverse or drive, and let it idle, it drops to 11.8-12.2 volts. The second I start driving, it goes to 13.2-13.5.

 

I can let it idle in park for hours, and it wont blow my tailight/running light fuse. I put it in reverse or drive and it is fine. The second I give it gas, it pops the fuse....I'm so lost. Could the alternator be faulty? (I replaced it 2 months go because the original one was shooting fire.) I checked the connections on it, and they seemed ok, however the positive bolt connection on top looked like the plastic was cracked.

 

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Alternator is spiking and blowing the circuit. Generally, it just blows bulbs.

Alternator is spiking and blowing the circuit. Generally, it just blows bulbs.

Yup...replaced the alternator again, put a fuse in, and it has been running for almost a week without popping a fuse....

 

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