atctkd

ls swap in my 79 Malibu. Has been running fine for the last 6 months. I went to wire up the A/C yesterday and ran into a problem with the fans. I have dual fans with the fan 1 and 2 control from the computer. I first wired a relay to jump the ground to fan 2 upon A/C request and that worked fine and everything was running ok. (as per instructions on lt1swap.com) After thinking about just the 1 fan pulling air across the condenser I thought it would maximize efficiency to have both fans turn on upon A/C request. So I took the ground coming from the relay I added, split that one wire into two via a butt connector and spliced into fan 1 as well as fan 2. Car started fine but as soon as I turned the A/C on, the under dash fuse popped and engine died(this was my key on power source for the fuses and relays) I replaced the fuse and now have a crank but no start. Sometimes it will stumble like it's going to fire and has an occasional crazy loud backfire. I have removed all of the fan jumper grounds and have got it to run for a few seconds and then it stumbles and shuts off, and the fans both seem to be running as the engine is running/stumbling.(which is odd to me) I seem to have power at the coil packs and injectors but no spark or injector pulse. Is it a possibility that wiring those two fans from the same ground at the same time somehow damaged the computer's ground circuit? I have pin tested the grounds at blue and red connectors and have continuity from pins to ground. Please help if you can. This is my son's daily driver and he just got a new job he needs to keep to pay his gas and insurance. Thanks a bunch

L92 OLDS

Did you wire in the check engine light and what codes do you have? It's plausible that the fan wiring cooked something in the ECM. Get a scan tool and check for codes. If you can get the car to AutoZone or Advance Auto they will check for free.

atctkd

No codes in the computer. Stored or provisional. What I did just remember is that previously when both fans were on and you shut the key off, the engine would continue to run until the voltage dropped below the point to hold the contacts of the mfi relays. Possibility of this backfeeding through the signal wire of the fan relays and frying stuff? I'm just wondering why the sudden pop of the fuse. I did notice the fans and mfi relay (key on +) were powered by the same fuse. Wonder if this was just too much amperage at one time for the fuse. I have since tapped into a different fuse for all 3 power circuits. I'm getting some diodes to wire into the fan power wires. Does anyone know the amperage of the f-body fans individually? Thanks...I appreciate the reply

atctkd

Finally figured this out yesterday. I originally had the key on power for both fans and the injectors tapped into the same fuse. When the circuit overloaded and popped the fuse, I moved the injectors to a different key on power source. Checked injector pulse again and had nothing while cranking but a small spike of voltage as the key was turned back from the start position(thus the stumbling and backfiring). Upon further diagnosis, I realized that the power to the injectors would disappear while cranking. Ended up separating the power source for each fan and moved the injectors power source back to the original spot with key on power while cranking....problem resolved. Hope this helps anyone else out there that makes the same "derp" move that I made. Anyhoo car is running great again and the A/C is blowing nice and cold just in time for the heat wave in AZ.