Cooling Fan Issues

My radiator cooling fan is driving me crazy. I have replaced the relay, fuse, fan motor and I still cannot get it to come on with the engine hot or by grounding the thermoswitch (I can hear the relay click, but fan motor will not turn). The fan motor is brand new and works fine connected directly to a 12 volt source. I believe I may have a wiring issue. Any suggestions?

When the relay clicks do you get 12V at the plug that goes into the fan motor?

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Originally Posted by POS Racing

When the relay clicks do you get 12V at the plug that goes into the fan motor?

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I have not put a meter on the fan connection when grounding the thermoswitch (I assumed if the cooling fan wasn't turning, there was no power) . I will test it this evening.

While doing the test if you haven't already. Inspect the wires going from the switch to the fan, and also ensure that the connections are clean as well. Any type of corrosion can inturupt signal. I don't know how the connect but if there are prongs for the male end make sure they are all straight as well. I had a car that the ac wasn't working on and found on inspection that one of my male prongs was bent side ways so it looked connected but actually wasn't. If you find this carefully straighten the prong and that should fix it. That is if that is the case. Sorry I can't be of more help, new to the Miata world.

Also.... if the fans were rigged to work in parallel by jumpering wires at the fans it could overload the wiring and damage the relay socket.

RJ

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Originally Posted by channelmaniac

Also.... if the fans were rigged to work in parallel by jumpering wires at the fans it could overload the wiring and damage the relay socket.

RJ

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I think I joined this club, but did not check the relay yet. Check pin 1R at the computer for continuity (switches to gnd), then see if you're getting voltage at the fan plugs when the car is hot (gnd pin 1r to test, like a deadshort).

Even if the relay clicks, it could still be toast...wiring issue?

If you have a 1.6 car, this is the proper way to do dual fans:


let us know what happens. The multi meter doesn't lie. Either you're getting current, or not...start from the computer and work your way to the fans. You either have a bad computer (doubtful), blown fuse, bad sensor, bad relay, bad wiring, or bad fan motor. Where does the signal die?

We know the fan motor works. Shorting the fan sensor wire doesn't make the fans come on, so we know that another problem is evident. Check the relay terminal and wiring next because I doubt the computer is toast.

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Originally Posted by Ben

Goal: Have first fan stage circuit excite at 175 F. Have second stage fan circuit excite at 206 F. Do not interfere with A/C control over pass side fan.

Result:
engine temp < 175 F = No fan
engine temp > 175 F & < 206 F = Single stage fan
engine temp > 206 = 2 stage fan (both fans running)
A/C on = A/C fan on, regardless of engine temp

Required items: SPDT relay, primary wire, crimp connectors, electrical tape, 30A fusible link

Instructions: The relay has 5 positions, wire as follows
Pin 30 to A/C side fan black/blue stripe wire FAN SIDE OF WIRE
Pin 85 to thermosensor
Pin 86 to +12V
Pin 87 NO to +12V (high power)
Pin 87a NC to A/C side fan black/blue wire on the CAR SIDE OF WIRE

You need a real automotive SPDT relay with a true NO contact and a true NC contact. The el cheapo $1.49 relays probably won't cut it. It should run $7-10.

You can grab +12V at the underhood fuse box. There are a variety of places. I had an unused position, so I crimped a spade connector onto a 14ga wire, and inserted it into the bottom side of the unused positon. Then reinstall the fuse block and insert a 30A fusible link. *(I ran this wire to both pin 87 (high power input) and pin 86 (switched 12V) so that my relay had power full time. If you wanted the relay to only work key on, you would need to run a switched on +12V source to pin 86.)

The A/C side fan has 2 wires. Leave the black wire alone. Cut the black/blue stripe wire. The side of the wire that goes to the fan connects to pin 30 on the relay. The side of the black/blue wire that comes from the car goes to pin 87a on the relay.

The thermosensor on top of the thermostat housing has only one wire. Cut it and bring it to pin 85 on the relay.

Tape everything up and make sure all your wiring is secured.

Enjoy

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all you wanted to know about fan problems on a 1991

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Originally Posted by channelmaniac

Also.... if the fans were rigged to work in parallel by jumpering wires at the fans it could overload the wiring and damage the relay socket.

RJ

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This whole issue started when I had the timing belt replaced. The mechanic unknowingly knocked off the rubber cap from the manual headlight knob and it got wedged into the rad fan. I am beginning to think this is a relay or relay socket issue (especially after reading another forum thread) . I still need to check to see if I am getting 12v at the fan motor connector.

If the relay clicks and the fan runs when direct wired then I must ask have you checked the fuse? Did you try to direct wire the old motor to see if it ran?

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Originally Posted by Flyin96M

If the relay clicks and the fan runs when direct wired then I must ask have you checked the fuse? Did you try to direct wire the old motor to see if it ran?

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I replaced the fuse initially, but need to recheck. I did direct wire the old fan motor and it would not run without me helping it, so it was bad.

Something you may look at is be sure that the fan blade is not hanging on the shroud or in some way binding up,also be sure that the motor does work have purchased new parts in the past that were bad
Just got through exchanging a throt pos sensor that was bad right out of the box.