Electric issues

So, I bought my first 07 speed3 in the beginning of the summer, and when I bought it I was told it was not running for more than 3 minutes at a time. After months of trying to figure it out, I had it at a mazda dealership where they told me it was just corrosion and a bad connection to the fuse box.

Okay. So now it is running, it had the turbo replaced with a cst4 which I'm in the process of getting it tuned with freektune. BUT, here's the problem I'm having. Everything electrical seems to be all out of wack. For one there are numerous check engine lights which should make the car immobile yet the car runs perfectly fine. The hazards turn on when the fan is at full speed. At night when the headlights are on, occasionally the turn signal would turn the headlights off completely and the dash light will also turn off for some time. And of course lights such as abs, tc, tpms, etc go on and then off at random times.

I have been trying to do some research into what I should do in this scenario. I am fairly certain there is either a) a bad connection to either a specific part or a fuse, b) something is getting grounded or has a bad ground, or c) something else that I am not aware of. I like working and learning on cars, but I'm not mechanic, especially when it comes to electrical problems.

Is there any steps I should take that could figure out a problem such as this? The car did sit for some time, so what would be some common things to replace for said car? Like I said I am in the process of getting it tuned with freektune currently, and would like to take care of this issue asap. Thanks.

 

The Speed6s have a ground grouping on the left frame rail behind the headlight (Bolt with white plastic rectangle). If the MS3s have it check that. I had some funny headlight/signal stoopidity and cleaning that cleared it up.

 

First gen 3's don't have multiple grounds on right fender from the main wire-loom that follows the radiator support. It has a few on pass side fender though.
When I rebuilt my 3, I removed motor from front. Metal membership offers almost all the first gen factory manuals, and there is a electrical system wireloom in them that can tell you the frame body ground points. Mazda uses a subsystem circuit breakout to show which circuit ground via the particular circuit and the chassis wire run and grounding points. You are going to have to check any or all ground points, and really since no one particular circuit is at fault. Everything will have to be visually checked. Sorry if sounds impossible but unless a consistent fault and repeating it's likely a important ground that causes ECU craziness.

 

I'll have to check that out.

 

So what was corroded and what did they replace? Did they just replace the fuse box and not the equally corroded wiring harness that connects to it?

 

All he told me was that he had cleaned up some wires to the fuse box, even the receipt just simply says "fixed wiring issue". I guess he said this was a "common problem", but not one I had ever heard of. I know he didn't replace the fuse box though. For example, after i got it back the following morning i turned the car on and everything was fine, turned it on again and it wouldn't even crank. Pulled out the fuse for the starter and put it back in, car started perfectly. So that's why I am fairly certain that there is still bad connections to fuses that I need to track down.

 

Then I would start by pulling the fuse box and checking it

 

Is there a certain way to remove the fuse box, like a diagram or something perhaps? Also would it be possible to just buy a new fuse box and put it in?

 

Never had to do it myself so I don't know, if you donate to the site there is a copy of the full shop manual available

 

Okay so I think it's just a bad alternator which should have been the obvious answer as I am assuming it has the same alternator since factory. I was locked out of my car the other day and had a mechanic come over and break in, found out the battery was at a super low voltage and was only running off of the jump pack. Gonna get that replaced next week and see if that fixes everything. In the meantime, can anyone tell me what other things I should consider replacing for a car that's been sitting for a while? Maybe some parts that are known for dying or failing regularly?