Fan Operation
05-30-15, 02:54 PM
#1
Fan Operation
I recently overhauled the coolant system in my FD. Everything, including all hoses, radiator, waterpump, etc were replaced. The car has a pettit thermostat (185 degrees) and an FC thermoswitch (Mazda OEM). The issue I'm having, is that the fans still do not switch on as far as I can tell, until 221 degrees F unless I turn on the AC. The car does in fact cool down to 175 to 185 degrees after the fans actually do come on, but I don't like the fact that the car runs up to 221F. I thought that with the edition of the FC thermoswitch, the fans would come on at a lower temperature and the temps would never reach 221F. I read and re-read Dale Clark's cooling thread, but there are 5 different discussions going on, and a lot of disagreement. Any ideas from the older guys, or guys running mostly stock cars?
05-30-15, 05:11 PM
#3
RX-7 Bad Ass
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The FC fan switch should kick on at (I believe) 97 deg. C. Stock is 107 deg. C.
If you want to test things, you can simply unplug the connector to the fan switch and ground the wire with a jumper wire. That should kick the fans on. If not, you have a wiring or connection problem somewhere.
The connector to the fan switch is usually an early casualty on wiring harnesses, so it's possible the wiring or connector is broken.
Dale
If you want to test things, you can simply unplug the connector to the fan switch and ground the wire with a jumper wire. That should kick the fans on. If not, you have a wiring or connection problem somewhere.
The connector to the fan switch is usually an early casualty on wiring harnesses, so it's possible the wiring or connector is broken.
Dale
05-30-15, 06:10 PM
#6
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the service highlights book has a nice chart of how the fans work. page F-60. http://foxed.ca/rx7manual/manuals/93...highlights.pdf
the fan motors have three speeds.
relay 1 is controlled by the a/c. relays 2 and 4 are controlled by the ecu
relay 3 is controlled by the thermoswitch.
relays 1-3 supply power to the fan motors, and relay #3 adds a ground.
so, when you turn on the a/c it turns on relay 1, and puts the fans in low speed. over 105-108c the ecu turns on relays 2 and 4, and with the a/c on this gives medium speed. high speed requires the thermoswitch to turn on, and then that turns on relay 3, which adds a second ground, and high speed.
if you have the a/c off, the fans go back a step, so everything is off until 105-108c, when relays 2 and 4 turn on, and this gives low speed. if the thermoswitch turns on, then you get a middle speed.
so the fan switch shouldn't turn the fans on sooner, it will just make them faster.
the fan motors have three speeds.
relay 1 is controlled by the a/c. relays 2 and 4 are controlled by the ecu
relay 3 is controlled by the thermoswitch.
relays 1-3 supply power to the fan motors, and relay #3 adds a ground.
so, when you turn on the a/c it turns on relay 1, and puts the fans in low speed. over 105-108c the ecu turns on relays 2 and 4, and with the a/c on this gives medium speed. high speed requires the thermoswitch to turn on, and then that turns on relay 3, which adds a second ground, and high speed.
if you have the a/c off, the fans go back a step, so everything is off until 105-108c, when relays 2 and 4 turn on, and this gives low speed. if the thermoswitch turns on, then you get a middle speed.
so the fan switch shouldn't turn the fans on sooner, it will just make them faster.
05-30-15, 08:40 PM
#7
Thats the confusing part and the purpose for my question. Some people say that the FC thermoswitch will turn the fans on at lower temps, and some say it makes them come on at the same temps, but male them spin faster.....if im correctly understanding everyone's replies.
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05-31-15, 10:23 AM
#8
RX-7 Bad Ass
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Each input just adds a fan speed. The thermoswitch at the back of the water pump housing is the most simple of the inputs, when it grounds it kicks up one fan speed, very simple circuit. The AC and ECU control circuits have a lot more to them.
If the fan switch is kicking on like it should, you should have fans coming on at 97 deg. C which you don't. That's why I'm saying to troubleshoot that first. Make sure the circuit is good by grounding out that connector then go from there.
Dale
If the fan switch is kicking on like it should, you should have fans coming on at 97 deg. C which you don't. That's why I'm saying to troubleshoot that first. Make sure the circuit is good by grounding out that connector then go from there.
Dale
06-01-15, 07:51 PM
#9
I have a mostly stock 95--aftermarket mods are downpipe, catback, boost controllers, interior ish (gauges, head unit). ecu OEM. using FC fanswitch
fans DEFINETLY come on before 221. are you sure you have the proper fan switch?
Also, where are you reading the temperature?
Last edited by 00SPEC; 06-01-15 at 07:54 PM.
06-02-15, 12:38 PM
#11
I just replaced the FC thermoswitch about 3 weeks ago, ordered it from Mazda brand new. Harness looked good when I installed it, but I'll check it again. Going to replace all relays in the car, as they are 20 years old anyhow. Thanks for all of the input from everyone.
06-13-15, 09:12 AM
#13
I'm going to start off with replacing the relays #2,3, and 4. They are 20 years old at this point, and with the exception of relay #1, they aren't an expensive part. The fans do operate when in turn the A/C on, so I'm going to hold off on relay #1 for now until I can figure out the problem. I only recently installed the FC Thermoswitch, ordered it from Mazda and inspected the harness upon installation, which looked fine. As of right now, I don't have overheating issues, it's just that the fans aren't turning on as soon as I want them to. I figure that before I dive into taking things apart again, I'll replace those relays. They should probably be replaced due to age anyhow,at this point. I'm going to order them this week, and I'll provide an update.
06-13-15, 11:54 AM
#14
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plan B, you could ground the relays manually, and see what they do.
07-19-15, 04:37 PM
#15
Update.....fixed!!!
Sorry for the delay, but life's been busy. Finally got around to replacing all of the relays. Replaced relay #2,3,4, as I knew that #1 was working when I turned on the A/C. I realize that I could have tested the relays individually, however, those relays are 20 years old, and cheap, so I figured I'd replace them anyway.
After replacing the relays, the fans now come on at 97C, or 206F. Considering that I have the FC thermoswitch, everything is now working perfectly. The way that I have come to understand how each relay plays into the equation, I assume that replacing relay #3 fixed the issue.
Thanks for all of the replies and help! Hope this helps anyone with the same issue.
Sorry for the delay, but life's been busy. Finally got around to replacing all of the relays. Replaced relay #2,3,4, as I knew that #1 was working when I turned on the A/C. I realize that I could have tested the relays individually, however, those relays are 20 years old, and cheap, so I figured I'd replace them anyway.
After replacing the relays, the fans now come on at 97C, or 206F. Considering that I have the FC thermoswitch, everything is now working perfectly. The way that I have come to understand how each relay plays into the equation, I assume that replacing relay #3 fixed the issue.
Thanks for all of the replies and help! Hope this helps anyone with the same issue.
08-09-15, 01:29 PM
#16
......and now not fixed. Worked for a short time, now fans wont activate without turning lights or AC on again. Im thinking bad ground. Anyone know of a list or diagram of all ground points in the engine bay? Or at least related to the fans?
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