cooling fans

[namyenruoj]

Hello,
we own a 91 MR2 Turbo and my cooling fans in front of cars don’t come on even if the car has been running for quite a while. i checked these fan relays 1,2 and 3 for functionality and they all work. but if i disconnect the water temp sensor on the radiator they all come on and stay on even when the ignition is at the on position only. would it be the water sensor the problem? thanks

[immorality]

If the car isn't overheating then it's not really a problem, as in, I don't think they need to come on. The MR2 cooling system is very large and has excellent cooling capacity. The fans should come on if the temp sensor is unplugged, it's meant to be a safety backup.

[camshaft]

Russ is spot on

If you have AC if you turn the compressor on the fans should come on as well

Other possibilities if your thermostat is stuck open the car could a very long time to heat up.

[namyenruoj]

i’ve decided to unplug the water temp sensor so the engine will nit over heat but then i will not resolve the problem. i’m still trying to figure out what make these fans to come on snd what are the sequence. thanks for all your info.

[immorality]

I don't think that's the best solution either. Check through the diagnostic procedures in the BGB, http://staff.osuosl.org/~bkero/bgb/mechanical/volume1/cooling_system.htm

[camshaft]

As russ pointed out your car hasn’t overheated yet?

If you are that sure a issues exists, you can take the sensor out of the rad. And heat it up on your stove with a thermometer
I’m not sure if the bgb has a chart or advanced diagnostics to say when the switch opens.

Sorry forgot to add you will need to have a voltmeter on the contacts to see when it triggers the fans

Or order a new switch and compare them or just replace it. Since you have verified the fans are working

[camshaft]

https://photos.app.goo.gl/HHiWGaMcVvQzjKvn7
I believe left is fan switch and right is coolant temp

[namyenruoj]

thank you guys. i will try to do that. the car will over heat if i left the engine running while the water temperature sensor is plugged in so i turn it off before it over heat and wait until it cools down a bit then restart again.

[entrax]

this turned out to be the thermostat. the coolant was cold on the pass side lines because the tstat was closed and no circulation was going on. Since the fan switch is also on the pass side of the rad, the fan switch area never got too hot enough to trigger the fans on.

when the switch was unplugged, this had the fan on full blast all the time, which was enough to cool down the car through just the one pipe on the drivers side. It helped enough to extend the time before it overheats.

new tstat, was all it took and the sensor turns on/off as normal.

[camshaft]

Thanks for update

I think the confusion was the car overheating, when I’m fact it wasn’t.

And of course thermostat on a Mr2 with AC is fun

this turned out to be the thermostat. the coolant was cold on the pass side lines because the tstat was closed and no circulation was going on. Since the fan switch is also on the pass side of the rad, the fan switch area never got too hot enough to trigger the fans on.

when the switch was unplugged, this had the fan on full blast all the time, which was enough to cool down the car through just the one pipe on the drivers side. It helped enough to extend the time before it overheats.

new tstat, was all it took and the sensor turns on/off as normal.