One of my radiator cooling fans will not operate on my 1993 Mazda Miata. After I checked the Fan relay, thermoswitch, and the TAF terminal and ground test point. Both will operater only when I use the Air Conditioner. Please give me a solution... tell me which part is bad!=-

Using a test light connect the lid to NEGATIVE and start the engine with A/C on.back probe the positive terminal on the fan.If no power test the fuse. if fuse OK switch the relay with the horn relay and test again. if you have a power to the fan connector switch the test light lid to POSITIVE on you battery and test for good ground to the fan.some times ground wire can corrode and create a lot of problems. If you have good Power and Ground replace the fan.
good luck

Are you talking about the radiator fan? How hot does the engine get in degrees F? Some makes and models, the radiator fan won't turn on till about 220 degrees F. Check for applicable trouble codes, see if any code that refers to the radiator fan circuit or coolant temp sensor? Some of the national brand auto stores will check codes for free.

Of course, as far as overheating in general, you have the thermostat--water pump and other possible issues. Are you losing coolant?

depending on the year, there should be 3 relays that control the fans.
There's a rad fan relay (4 pins), an a/c condensor fan relay (4 pins), and a fan control relay (5 pins). This allows them to be run at low speed or high speed. Check the grounds behind/under the righthand headlamp.
Check Fuses 57, 58 (30 Amps) and fuse 46 (15A) under the hood, and fuse 3 (7.5 Amps) in the driver's underdash fusebox.

I would want to know if the computer is grounding the fan relay to make it come on, or if the relay is faulty. On some models the computer turns the fan on to keep the radiator from overheating when the engine is stopped, but that should only happen with the engine at operating temp.

Here are the cooling system diagnostic steps...First does the cooling fan kick on (with engine hot)? If not, check the fuse, if good then check the thermoswitch in the radiator (it's about an inch and a half in diameter located on the lower part of the radiator with two wires ) by disconnecting the wires and touching them together (again, with engine hot...at least 190 degrees) if the fan comes on, you have a bad switch. If not connect a 10 gauge jumper wire from the battery to the fan itself (there are three terminals,,, one high, one low and ground). With power direct from the battery (and a ground wire, if necessary) fan should run... if not replace the fan assembly... if it does run then you have a bad cooling fan relay. It will be located above the fuses on the fuse block... Hope this helps...;-)

Here are the cooling system diagnostic steps...First does the cooling fan kick on (with engine hot)? If not, check the fuse, if good then check the thermoswitch in the radiator (it's about an inch and a half in diameter located on the lower part of the radiator with two wires ) by disconnecting the wires and touching them together (again, with engine hot...at least 190 degrees) if the fan comes on, you have a bad switch. If not connect a 10 gauge jumper wire from the battery to the fan itself (there are three terminals,,, one high, one low and ground). With power direct from the battery (and a ground wire, if necessary) fan should run... if not replace the fan assembly... if it does run then you have a bad cooling fan relay (under the dash, I believe). Hope this helps... ;-)

problem sounds like either the thermoswitch in the radiator or the cooling fan relay under the dash... test by removing wires from thermoswitch and test for continuity at the terminals with a meter (radiator cold)... if you have continuity the switch is bad... if not it's the relay (fused closed... replace it)... Hope this helps...;-)

check the fuse, if good then check the thermoswitch in the radiator (it's about an inch and a half in diameter located on the lower part of the radiator with two wires ) by disconnecting the wires and touching them together ( with engine hot...at least 190 degrees) if the fan comes on now but didn't before, you have a bad switch. If fan does not come on connect a 10 gauge jumper wire from the battery to the fan itself (there are three terminals,,, one high, one low and ground). With power direct from the battery (and a ground wire, if necessary) fan should run... if not replace the fan assembly... if it does run then you have a bad cooling fan relay. Compressor choice depends on your finance... a rebuilt unit is going to be a lot cheaper... Hope this helps... ;-)

Here are the cooling system diagnostic steps...First does the cooling fan kick on (with engine hot)? If not, check the fuse, if good then check the thermoswitch in the radiator (it's about an inch and a half in diameter located on the lower part of the radiator with two wires ) by disconnecting the wires and touching them together (again, with engine hot...at least 190 degrees) if the fan comes on, you have a bad switch. If not connect a 10 gauge jumper wire from the battery to the fan itself (there are three terminals,,, one high, one low and ground). With power direct from the battery (and a ground wire, if necessary) fan should run... if not replace the fan assembly... if it does run then you have a bad cooling fan relay. If the cooling fan system is working normally and you still are overheating, the next thing to check is for coolant flow. let the engine cool and remove the reservoir cap and start it and let it run to operating temp. The upper hose should warm up and you should see a thin stream of coolant entering the reservoir... if not let it cool again, raise the vehicle, place a drain pan beneath the engine and remove the T-stat from the housing and button it back up. run again to operating temp... if you now have flow, and it doesn't overheat it was the 'stat. If it still overheats look at the water pump... is it noisy while running? is it weeping coolant? if so replace the pump. if not it's time to suspect a radiator blockage... try backflushing, if it seems to take alot of pressure and very little come out the other outlet the radiator is at least partially clogged and should be rebuilt or replaced... Hope this helps...;-)

ground the wire sensor and see if fan work if not change the relay, first check fues.