Hello, I have been trying to get my fc running recently. I bought a new battery, hooked it up and main fuse blew. I bought another main from Atkins and hooked it up and it blew again the second I hooked the battery back up. I'm new to cars in general and new to rotaries, i've owned my fc since 2018 but drove it a handful of times since I was trying to learn to drive manual on it and has been sitting for awhile. I have basic car knowledge, I still have to check if any open wires are touching the body and all, but I can't figure out what else it could be.

Photo i attached is the fuse second after it happened.
(the others look blown too, also the headlights wont go up anymore, no click either when trying to start/jump wont work, rear lights dont work but interiors do)
ty in advance

 

Did you put the battery in backwards? The negative terminal is the one closer to the front of the car, and it has a longer cable on the harness to account for that.

 

If your problem is not reversed polarity, you need to break out the multimeter, remove the battery, replace the main fuse and start by (correct me I’m wrong) checking continuity to ground.

Positive battery terminal to ground should show open circuit. If it reads a closed circuit, you need to start disconnecting each of the main power cables one by one and repeating the test (starter, alternator, etc.)

 

I did something similar one time, installed a customers hard to get to alternator on an old Alfa. Cranked everything down, hooked it up, big flash, lots of smoke.

Turns out when tightening the positive lead to the alternator it rotated as it was being tightened and contacted the alternator case. Huge short, blew the whole wire right up. Not a fun day haha.

 

You have a short somewhere. Since it's the Main Fuse that keeps popping, it's gonna be kind of a pain to isolate, going through the entire power delivery system and playing a game of "one of these things is not like the others". Do you have the S5 (89-91) Factory Service Manual and Wiring Diagrams? If not, you can grab them for free at foxed.ca

Anyway, before doing anything, I'd suggest taking a picture of both fuse boxes for comparison against the stock ratings (see the FAQ) and see if anything is out of order. Based on it popping a 100A fuse repeatedly, this would imply a rather large short on a considerably heavy gauge cable (think 8awg or more). A short on smaller wiring such as the Meter Fuse would pop a smaller fuse due to less current being available. A good rule of thumb is that if a circuit has more than one fuse, the lowest rated fuse will pop first and the short will always be downstream of the popped fuse. For example, if a circuit runs through a 40A fuse under the hood, then a 15A one inside, and the short is at the very end of the circuit, the 15A fuse will pop first. If the short is between the two fuses, the 40A fuse would pop first (closer to battery than the 15A one)

Also, this might sound dumb, but fuses can be found at any parts store. The Main Fuse is a "FLM" type Fusible Link. Here they are at Autozone: https://www.autozone.com/electrical-...E&gclsrc=aw.ds

Roughly where are you at in Ohio? If you're near the IN border, I might be able to lend a hand in a few weeks once work settles down.