DGblk93

I thought this was kinda odd. I was showing the car to someone the other night and I discovered a 'trick'. When the car was idling in the driveway we had the hood open. I switched on the running lights, and the fans immediately came on. I turned off the lights, and they stayed on for their normal cycle (about 30 seconds). I can do this over and over if I want. Lights on, fans on. I'm kind of a new FD owner (6 months) - does anyone else get this? Does everyone else get this?

patfat

Yep, that's normal.

TwinTurbo93

Hehe, the running light do turn the fans on few degrees before, also the rear glass defroster and the heater fan on 3rd speed do the same... Perfectly normal for an FD but don't ask me why

DGblk93

That's great. I was showing it to an an older muscle car guy (he really admired the car) - and we both laughed at the discovery. Thanks.

FDjunkie

As patfat says this is normal behavoir for the FD whenever the engine coolant temperature is between 100~104 degrees C (212~212 F). The actual trigger is the E/L (electrical load) system that monitors several high-load electrical curcuits as mentioned by TwinTurbo93. Above this temperature the fans are on regardless of the E/L, and the fans speed increases as the coolant temperature goes on up.

DGblk93

^ since you brought it up - what is considered a dangerous coolant temp?
Thanks

FDjunkie

Lots of opinions on this issue, but many might agree that anything above 105 degrees C (220 F) begins to more rapidly increase the potential harm. That's not to say that occasionally reaching 106 or 107 or 108 C will magically cause catastrophic failure. I think this is a time-at-temperature situation; the more time spent at higher temperatures the greater the toll.

Attached is a table I put together from examining FWM, posts, etc. It shows how Mazda designed the cooling fan behavior with respect to coolant temperature. Notice that they progressively increase the fan speeds as the temperature increases, and that above 117 C (243 F) they even disable the A/C.

Also, remimber that what we see on our temperature gauges, and what the ECU monitors, are only average temperature values. There are always higher peaks and hot spots that go un-noticed on all engines, but the rotary with its 'rubber' coolant seals, etc. is probably less tolerant of these real-life situations. Just food for thought...

RX7UP

Wow, really? I didn't know that! Automaticly disabling the AC if temps rise past a certain point.... Sweet!...... Mazda engineers were really using they're heads.... and here I was sweating through the summers with my AC off to prevent accessive heat....