Electrical issue after replacing radiator

  • 2009 MAZDA RX8
  • 1.3L
  • 2WD
  • 70,000 MILES
Car listed above is a Series 2 Mazda RX-8. I recently replaced the radiator, which isn't difficult but requires much disassembly of the front end. I got it put back together and running. As I was purging air from the system, I noticed the radiator fans weren't turning on. I was monitoring the coolant temperature via a Bluetooth OBDII scanner and it was hot enough that they should have switched on. I shut the car down and decided to pull the three fan relays from the main fuse block and bench test them. They all functioned properly. I reinstalled them in the fuse block and turned the ignition to ACC. I didn't hear the normal sounds of the fuel pump and air pump starting up. Instead, I heard a relay clicking continuously. This was different from when there is something like a bad battery. This was a constant click. I shut off the ignition and disconnected the battery (which is almost new and never had a problem with it). I waited about 5 minutes and reconnected the battery, and switched the ignition to ACC again. Same result - constant clicking of a relay. I looked around under the hood to see if I could identify the source of the sound. I then heard a loud "click" and everything went dead; nothing, even interior lights, was working. I disconnected the battery again and looked for blown fuses. I found the EGI Comp2 fuse had blown. I have a Mazda service manual for he car and started following the troubleshooting, starting with the radiator fan relays, doing what I could without connecting he battery. For each of the three fan relays in the main fuse block, I discovered there was continuity between one of the relay terminals and the body ground for all three relays, indicating a ground short (most likely melted wires somewhere). The service manual says to repair or replace the wiring harness for corrective action. I do my own work, but I'm not sure where to start.
Do you
have the same problem?
Tuesday, March 31st, 2020 AT 5:08 AM

1 Reply

Sorry for the delay. Not sure why we didn't see this earlier. Looking at this and all the testing you have done, what I would suggest at this point is to create your own wiring for a temporary test. Basically just take some jumper wire and run your own wiring to replace the wiring from the EGI Comp 2 fuse to each of the relays it feeds.

I agree that this appears to be your issue so once you confirm it is with jumper wires, then you can simply solder in new wiring and secure it with zip ties to the existing harness.

Let me know if you have questions. Thanks
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Thursday, April 2nd, 2020 AT 10:12 AM

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