FC Thermoswitch in 108 degree weather
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FC Thermoswitch in 108 degree weather
I have a fairly stock FD with only reliability upgrades and modifications, and today reached 108 degrees here in Sacramento and I must say that I am impressed at my engine temps.
Everything is stock : radiator, intercooler, engine, stock converters, only cooling mod is the fc thermoswitch and aluminum ast. I didn't even realize that it was that hot outside, but I realized in traffic my coolant temps reached 220 max which was a little warmer then my usual but still considered normal, but when I realized it was about 108 degrees outside, I realized that's not bad!
I ran the car hard for several hours in the extreme heat testing my boost not realizing how hot it was and the coolant temps on average stayed at about 190-205 degrees with hard driving, then the cooling fan stays on for 10 minutes to cool the engine while the car is shut off.
I would strongly recommend every FD owner with a fairly stock FD who wants to slightly upgrade the cooling system without performing extensive and expensive modifications, get a FC Thermoswitch. Totally worth it
BTW it was so hot today my temp gauge was reading 140 degrees after the car had been sitting for 8 hours
Everything is stock : radiator, intercooler, engine, stock converters, only cooling mod is the fc thermoswitch and aluminum ast. I didn't even realize that it was that hot outside, but I realized in traffic my coolant temps reached 220 max which was a little warmer then my usual but still considered normal, but when I realized it was about 108 degrees outside, I realized that's not bad!
I ran the car hard for several hours in the extreme heat testing my boost not realizing how hot it was and the coolant temps on average stayed at about 190-205 degrees with hard driving, then the cooling fan stays on for 10 minutes to cool the engine while the car is shut off.
I would strongly recommend every FD owner with a fairly stock FD who wants to slightly upgrade the cooling system without performing extensive and expensive modifications, get a FC Thermoswitch. Totally worth it
BTW it was so hot today my temp gauge was reading 140 degrees after the car had been sitting for 8 hours
#2
rotorhead
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The fan speeds are increased in steps.
On a stock ECU, the FC thermoswitch will turn the fans on at 207F/97C and keep them on until they drop down to 194F/90C. Then the ECU will speed the fans up at 105C/221F. The A/C will also increase fan speeds independent of coolant temperature. These are pretty much the same trigger temperatures that the Rx-8 uses from the factory.
If you had a stock FD thermoswitch, the ECU would first turn the fans on at 105C/220F. Then the FD thermoswitch will speed them up at 108C/227F. The A/C will also increase fan speeds independent of coolant temperature.
If you have a Power FC you can change the temperature at which the ECU triggers the fans. But that only controls one "step" of fan speed. The other two "steps" are independent of the computer. So the FC thermoswitch is a valuable mod on both the stock computer and the Power FC. The thermoswitch is also used to trigger the aftercool function in the cooling fan control module, so with the FC thermoswitch your fans may be more likely to stay on for a 10 minute period after you shut the car down.
On a stock ECU, the FC thermoswitch will turn the fans on at 207F/97C and keep them on until they drop down to 194F/90C. Then the ECU will speed the fans up at 105C/221F. The A/C will also increase fan speeds independent of coolant temperature. These are pretty much the same trigger temperatures that the Rx-8 uses from the factory.
If you had a stock FD thermoswitch, the ECU would first turn the fans on at 105C/220F. Then the FD thermoswitch will speed them up at 108C/227F. The A/C will also increase fan speeds independent of coolant temperature.
If you have a Power FC you can change the temperature at which the ECU triggers the fans. But that only controls one "step" of fan speed. The other two "steps" are independent of the computer. So the FC thermoswitch is a valuable mod on both the stock computer and the Power FC. The thermoswitch is also used to trigger the aftercool function in the cooling fan control module, so with the FC thermoswitch your fans may be more likely to stay on for a 10 minute period after you shut the car down.
#7
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I agree, the FD stock cooling system is not THAT bad.
I have a stock radiator with a FMIC and i have never seen outrageous temps.
Just recently was i caught in a one hour DEAD stop traffic jam in 95 degree weather. It literally took me 1 hour to travel 2 miles. They completely blocked off the turnpike and everyone had to make the same exit lol
I was very surprised at how my temps steadied.
Of course i had my fans running the entire time but still, it never went past 205F. And i had already been driving 45 minutes prior to that. So almost 2 hours total in 95 degree weather and my temps never went above 205F, with the stock rad and a FMIC.
And yeah there are times when my car has sat for days and i go start it up in this hot weather and temp shows like 120F already lol. But i still warm it up though lol.
I have a stock radiator with a FMIC and i have never seen outrageous temps.
Just recently was i caught in a one hour DEAD stop traffic jam in 95 degree weather. It literally took me 1 hour to travel 2 miles. They completely blocked off the turnpike and everyone had to make the same exit lol
I was very surprised at how my temps steadied.
Of course i had my fans running the entire time but still, it never went past 205F. And i had already been driving 45 minutes prior to that. So almost 2 hours total in 95 degree weather and my temps never went above 205F, with the stock rad and a FMIC.
And yeah there are times when my car has sat for days and i go start it up in this hot weather and temp shows like 120F already lol. But i still warm it up though lol.
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I ran the car hard for several hours in the extreme heat testing my boost not realizing how hot it was and the coolant temps on average stayed at about 190-205 degrees with hard driving, then the cooling fan stays on for 10 minutes to cool the engine while the car is shut off.
#10
Recovering Miataholic
Recently (at ~102 K miles) took the forum advice and installed the FC thermoswitch. Most noticeable effect on this near-stock '94 is the increased frequency of fans running after shutoff. Wife is worried about shortened battery life. I checked battery voltage just after the fans shut down; measured 12.45 volts across battery terminals. Fully charged, the battery sits at about 12.6 volts; I can't see the fan current drain as a future battery problem. Any opinions on this?
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Recently (at ~102 K miles) took the forum advice and installed the FC thermoswitch. Most noticeable effect on this near-stock '94 is the increased frequency of fans running after shutoff. Wife is worried about shortened battery life. I checked battery voltage just after the fans shut down; measured 12.45 volts across battery terminals. Fully charged, the battery sits at about 12.6 volts; I can't see the fan current drain as a future battery problem. Any opinions on this?
#12
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For anyone in NZ - I just bought a FC Thermoswitch PN41-18-840 from John Andrew Ford/Mazda yesterday for $70NZD. Easy to get, but needs to be shipped in from Japan.
#13
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I too have the FC switch. One additional thing that I did during installation was to splice in an additional length of wire--a loop up to the air pump area--with a switch in series. The purpose of this is to be able to defeat the thermoswitch and allow the temps to come up to higher levels to assist in passing emissions tests (and/or for cold weather operation, if you need more heat).
#14
Recovering Miataholic
I too have the FC switch. One additional thing that I did during installation was to splice in an additional length of wire--a loop up to the air pump area--with a switch in series. The purpose of this is to be able to defeat the thermoswitch and allow the temps to come up to higher levels to assist in passing emissions tests (and/or for cold weather operation, if you need more heat).
#15
rotorhead
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Recently (at ~102 K miles) took the forum advice and installed the FC thermoswitch. Most noticeable effect on this near-stock '94 is the increased frequency of fans running after shutoff. Wife is worried about shortened battery life. I checked battery voltage just after the fans shut down; measured 12.45 volts across battery terminals. Fully charged, the battery sits at about 12.6 volts; I can't see the fan current drain as a future battery problem. Any opinions on this?
Here is where the fan control module and the multi-speed fan control system are truly advantegous. The fans run for 10 minutes max due to a timer in the cooling fan control module. The fans are also throttled down in speed. When aftercool begins, the fans run at medium speed. Once the thermoswitch cuts off (temps drop enough) the fans slow down to low speed until the 10 minute timer expires. The system was engineered well enough to prevent a major battery drain on a car with a healthy electrical system. That being said, running the fans after shutdown certainly doesn't do the battery any favors. But one of the reasons Mazda put the fan control module in was to keep the engine bay from getting so hot that hoses would start to bake. FYI the Rx-8 also has an aftercool system that can be triggered by an engine bay temperature sensor:
Anecdotally, some 2nd gen cars with electric fan conversions run off a thermoswitch only and have no timer circuit. So the fan will run continuously (usually a single speed fan) until the temps drop without any throttling or timer circuit. I haven't heard of any battery drain problems occuring even in those kinds of setups.
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Recently (at ~102 K miles) took the forum advice and installed the FC thermoswitch. Most noticeable effect on this near-stock '94 is the increased frequency of fans running after shutoff. Wife is worried about shortened battery life. I checked battery voltage just after the fans shut down; measured 12.45 volts across battery terminals. Fully charged, the battery sits at about 12.6 volts; I can't see the fan current drain as a future battery problem. Any opinions on this?
So...was this with the A/C on or off? My car is currently in pieces 'cause I'm installing the FC thermoswitch and a new thermostat. I'm hoping the thermoswitch will keep my temperatures under 100C when I'm running the A/C. Currently, with the A/C on, my temperatures will ever so slowly creep up to 100 and beyond...and I already have a PowerFC which is set to add a speed at 95C.
I too have the FC switch. One additional thing that I did during installation was to splice in an additional length of wire--a loop up to the air pump area--with a switch in series. The purpose of this is to be able to defeat the thermoswitch and allow the temps to come up to higher levels to assist in passing emissions tests (and/or for cold weather operation, if you need more heat).
#18
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Oh yea it can [affect emissions].
If you are right at the limit, like I am, building all the heat you can will generally improve your chances of passing the tests. Even with a good cat, airpump, ignition, tune and all the emissions controls, etc., my large ported /high overlap motor just squeeked by the CA emissions tests--but only after getting the temps way up.
I grant you this will be less of a concern for a stocker or near-stocker and those with less aggressive porting setups, etc..
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Metan, DaleClark has already made a thread about that.
I'm about to get a FC-switch and do this mod. I also have a stock ECU. But looking at the wiring diagram makes me wounder if the fans really will come on at 97C.
The thermoswitch just adds another grounding point to the fans, there will be no voltage at the fans, thereby no rotation. So an FC-switch with stock ECU should give the following operation,
Those who tried, am I right?
I'm thinking about rewiring the relays to recover the stock way of operation. But I don't understand why the ECU needs to control TWO relays??
I'm about to get a FC-switch and do this mod. I also have a stock ECU. But looking at the wiring diagram makes me wounder if the fans really will come on at 97C.
The thermoswitch just adds another grounding point to the fans, there will be no voltage at the fans, thereby no rotation. So an FC-switch with stock ECU should give the following operation,
Those who tried, am I right?
I'm thinking about rewiring the relays to recover the stock way of operation. But I don't understand why the ECU needs to control TWO relays??
#21
Recovering Miataholic
#22
Recovering Miataholic
I'm about to get a FC-switch and do this mod. I also have a stock ECU. But looking at the wiring diagram makes me wounder if the fans really will come on at 97C.
After installing the FC switch on our '94, the after-switch-off fan running time has not changed much, but the fans operate in that mode much more frequently than during the previous mileage (102K miles) on the FD switch.
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The reason why I know for a fact that the fans do come on at 207F or 97C, is because I put an aftermarket temp gauge and I let the car idle for about 30-45 minutes and watched my engine temp keep rising slowly, until the needle stopped rising around 205ishF and it didn't increase anymore. At that point I did hear the fans kick on.
#24
Racecar - Formula 2000
I do that EVERY time I park in the garage! Good advice!
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I also meant the "Engine Coolant Temperature Switch" when I said "thermoswitch".
Exactly, it just adds ground to the fan motor and two grounds shouldn't make the motor run.
But it seems to run for Ernesto13B, have to short my relay and observe.
But it seems to run for Ernesto13B, have to short my relay and observe.