Add-on fan

Fly-In Miata is one source if you really need a bigger A/C fan. As old as a 90 is, I'd wonder about the radiator's efficiency, due to crud build up inside. The A/C compressor is also suspect. One way to add an "extra" fan is to place a "pusher" fan on the front of the radiator.

I have a turbo'd 99, and it uses stock fans with a larger capacity radiator and a 180deg thermostat.

I live in Phoenix, AZ where we have pleasantly warm days of up to 122F. My 150,000 mile 1992 Miata does NOT overheat with the AC on. If yours does, you have a problem and an extra fan is a workaround, not a fix.

Remove the radiator and have it flushed, make sure all components are working correctly and don't forget the often overlooked overheating culprits: brakes dragging and wheel alignment!

To answer your question, the best place to connect would be in parallel with the existing AC fan.

If I had to add a fan, I'd likely use a relay triggered from the appropriate fan circuit, and a separate added power circuit with fuse.

I believe the AC fan already has a relay, connecting in parallel should be no problem if the relay has the capacity, if not, there's higher current relays available.

I can't find current specs on the relay right now but your parts guy would know....

It does, at least on my 99. The concern I have is more related to stock wire size, and a desire to change the stock wiring as little as possible. Adding an additional relay and power side wiring with the relay coil driven from the original wiring seems best to me. I might also add a temperature sensor, so that the added fan comes on only when needed. In addition, I'd likely add the fan to the front of the radiator as a pusher. Remember, my 99 is turbo'd, and there is not a lot of excess cooling capability.

Thanks for the information.

There is another little detail that I ran across on the 99. The gauge temp sensor is at the front of the engine, and the computer sensor at the rear. I use a "Scan Gauge II" to monitor the temperature readings and other stuff that the computer sees via it's sensors. The rear temp sensor generally is higher that the front when the engine is fully warm, and colder than the front when the engine is warming up. This might be part of for the 99 "idle dip" problem, assuming that the computer thinks the engine temperature is uniform.

Anyway, the rear sensor often shows a reading of about 20 deg F higher than the thermostat, so a 200-210 thermostat and "normal" gauge reading can easily result in a rear temperature higher than you would prefer, and one that stresses underhood stuff, due to heat. (No wonder there were problems with the 99-2000 ignition coil packs) A 180 degree thermostat, due to production variations, may not reduce things enough, and a 160 thermostat impacts gas mileage. Given that my 99 has an oversize aftermarket radiator, I'd think things might be even worse in terms of front to back temperature difference with a stock radiator.