E-Fan questions
fails.....
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here is some info that might answer your question. I didn't exactly understand what you were talking about, but I think that is because I've been up all night... lol...
this isn't my words, I stole them from here. it mentions things like RX7s and what not, but the info is generalized enough, it applies to all cars.
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Wiring
This is perhaps the most critical section, and probably the most overlooked and misunderstood. There are many wrong ways to wire an e-fan, and they all are demonstrated during the frequent electric fan discussions on the various forums and mailing lists.
Probably the worst thing that people do is to wire the fan to a switch in the cockpit. This is the Zen concept of your "inner thermostat". Unfortunately, this built in thermostat is unreliable. The idea here is that you watch the temperature gauge, and manually turn the fan on at idle or when the temps begin to climb during low-speed creeping. The flaw in this idea should be obvious. For one thing, people are far from perfect, and can easily forget to engage the fan. In addition, the temperature gauge in the '89+ cars is horrible. By the time it has moved from it's normal (middle) position, the car is already too hot. It is entirely possible to have a defective temperature gauge, and the stock unit is only a relative indication of the true temperature of the car.
The opposite of this is to wire the fan to operate anytime the car is running. It is connected directly to a 12V IGN source, perhaps through a relay. There is a major problem with this setup in that the fan is only required when sitting stationary or driving slowly. At cruise, a spinning fan is just an unnecessary load on the electrical system. The fan loads an already factory-overloaded electrical system since the factory 2nd gen alternator is either rated at 70A ('86-'88 or 90A ('89-'92). These ratings are optimistic, and actual output is somewhat less. Adding a constant 10A draw on this system is quite a bit of stress. In addition, even if you did free up a miniscule amount of engine horsepower by removing the slight inertia of the stock fan clutch, you are now burning it up (and more!) as the alternator puts more strain on the engine to produce the current necessary to run the fan.
Now that we've covered what you shouldn't do, we will explain how to correctly wire your fan.
The most important concepts are: fuse, thermostat, relay. The fuse is perhaps the most important part, as it is all that stands between a wiring problem and electrical meltdown. It is critical that this fuse be located as close to your +12V source as possible, and be rated for "just enough" current to start and run the fan without allowing much overhead. This is one part most commonly missed.
The thermostat (or thermal switch) is simply the control device. The thermostat in your cooling system controls water flow through the rad depending on engine temperature. The fan thermostat controls the fan, turning it on when needed and off when not. These thermostats are available from most electric fan suppliers, as well as Summit Racing. Searching the Summit online catalogue for "thermostat" or "fan switch" will quickly turn up several. The best are all electronic, but the electromechanical work as well. Just be aware that they may stick if they get dirty. As far as I know, all fan thermostats are adjustable, but you might want to verify that the model you are looking at is before you buy. Skipping the thermostat and just using a switch is not recommended, for reasons explained above.
Even though most thermostats have high-current contacts built in, it is important that you use a relay to switch the fan. As mentioned, electric fans pull large startup currents. This causes arcing on the switching contacts, which will wear them out over time. Using a relay means that you will wear the contacts in a cheap relay, and not an expensive thermostat. The relay is also designed for high-current abuse, whereas the thermostat contacts might not be as robust.
Now that we've covered the basics of what you need, let's wire it up. As you can see on the schematic below, it is fairly straightforward.
The schematic above will activate the fan anytime the coolant temperature is above the threshold of the thermostat. This means that the fan could continue to run for a few minutes even after the engine is shut off (on hot days). To avoid this, and set up the fan so that it can only run when the engine is on, use the schematic below instead.
If your car is a 2nd gen RX-7, then switched 12V can come from the green 6 pin diagnostic connector near the battery (black/yellow wire). Otherwise, the black/yellow wire near the leading ignition coil is another good choice.
If your car is a 1st gen RX-7 you will find that the black/white wire around the ignition area to be a good source of a switched 12V signal.
Power for high current devices like fans should be taken directly from the battery. This avoids loading down other circuits which may not be able to handle high currents. The fuse is absolutely necessary, and should be located as close (physically and electrically) to your 12V source as possible. 30A is a typical value, but if you can get by with a smaller fuse by all means use one. You will see that we use the thermostat to activate the relay, which then switches the fan. Grounding can be any common source, but it is best to make your ground as short as possible. If you use the chassis as ground, make sure to scrape away any paint that could interfere with your connection.
The thermostat will typically have a probe that is to be positioned on the radiator somewhere. I like to put mine into the fins in the corner where the upper rad hose connects. This is the hottest area of the radiator, and a generally convenient spot. It should go without saying that the thermostat be located away from moisture, dirt and excessive heat. Now that you have everything wired up, the thermostat will need adjusting. Start conservatively with the fan coming on well below operating temperature, and then gradually increase the temperature setting until the fan maintains the proper (quarter gauge on the '86-'88 cars, half gauge on the 89+ cars) temperature. If you are unsure as to the accuracy of your stock temperature gauge, you absolutely must verify your readings with another source. Either an aftermarket temperature gauge (with it's sender installed before the thermostat) or a thermometer. The fan should turn on around 190 degrees or so in most cases as the thermostat is supposed to open around 177-183 degrees F. The fan should not fight the water-thermostat in maintaining temp, and should only run for a few seconds after the car is turned off (unless the car is very hot).
this isn't my words, I stole them from here. it mentions things like RX7s and what not, but the info is generalized enough, it applies to all cars.
-----
Wiring
This is perhaps the most critical section, and probably the most overlooked and misunderstood. There are many wrong ways to wire an e-fan, and they all are demonstrated during the frequent electric fan discussions on the various forums and mailing lists.
Probably the worst thing that people do is to wire the fan to a switch in the cockpit. This is the Zen concept of your "inner thermostat". Unfortunately, this built in thermostat is unreliable. The idea here is that you watch the temperature gauge, and manually turn the fan on at idle or when the temps begin to climb during low-speed creeping. The flaw in this idea should be obvious. For one thing, people are far from perfect, and can easily forget to engage the fan. In addition, the temperature gauge in the '89+ cars is horrible. By the time it has moved from it's normal (middle) position, the car is already too hot. It is entirely possible to have a defective temperature gauge, and the stock unit is only a relative indication of the true temperature of the car.
The opposite of this is to wire the fan to operate anytime the car is running. It is connected directly to a 12V IGN source, perhaps through a relay. There is a major problem with this setup in that the fan is only required when sitting stationary or driving slowly. At cruise, a spinning fan is just an unnecessary load on the electrical system. The fan loads an already factory-overloaded electrical system since the factory 2nd gen alternator is either rated at 70A ('86-'88 or 90A ('89-'92). These ratings are optimistic, and actual output is somewhat less. Adding a constant 10A draw on this system is quite a bit of stress. In addition, even if you did free up a miniscule amount of engine horsepower by removing the slight inertia of the stock fan clutch, you are now burning it up (and more!) as the alternator puts more strain on the engine to produce the current necessary to run the fan.
Now that we've covered what you shouldn't do, we will explain how to correctly wire your fan.
The most important concepts are: fuse, thermostat, relay. The fuse is perhaps the most important part, as it is all that stands between a wiring problem and electrical meltdown. It is critical that this fuse be located as close to your +12V source as possible, and be rated for "just enough" current to start and run the fan without allowing much overhead. This is one part most commonly missed.
The thermostat (or thermal switch) is simply the control device. The thermostat in your cooling system controls water flow through the rad depending on engine temperature. The fan thermostat controls the fan, turning it on when needed and off when not. These thermostats are available from most electric fan suppliers, as well as Summit Racing. Searching the Summit online catalogue for "thermostat" or "fan switch" will quickly turn up several. The best are all electronic, but the electromechanical work as well. Just be aware that they may stick if they get dirty. As far as I know, all fan thermostats are adjustable, but you might want to verify that the model you are looking at is before you buy. Skipping the thermostat and just using a switch is not recommended, for reasons explained above.
Even though most thermostats have high-current contacts built in, it is important that you use a relay to switch the fan. As mentioned, electric fans pull large startup currents. This causes arcing on the switching contacts, which will wear them out over time. Using a relay means that you will wear the contacts in a cheap relay, and not an expensive thermostat. The relay is also designed for high-current abuse, whereas the thermostat contacts might not be as robust.
Now that we've covered the basics of what you need, let's wire it up. As you can see on the schematic below, it is fairly straightforward.
The schematic above will activate the fan anytime the coolant temperature is above the threshold of the thermostat. This means that the fan could continue to run for a few minutes even after the engine is shut off (on hot days). To avoid this, and set up the fan so that it can only run when the engine is on, use the schematic below instead.
If your car is a 2nd gen RX-7, then switched 12V can come from the green 6 pin diagnostic connector near the battery (black/yellow wire). Otherwise, the black/yellow wire near the leading ignition coil is another good choice.
If your car is a 1st gen RX-7 you will find that the black/white wire around the ignition area to be a good source of a switched 12V signal.
Power for high current devices like fans should be taken directly from the battery. This avoids loading down other circuits which may not be able to handle high currents. The fuse is absolutely necessary, and should be located as close (physically and electrically) to your 12V source as possible. 30A is a typical value, but if you can get by with a smaller fuse by all means use one. You will see that we use the thermostat to activate the relay, which then switches the fan. Grounding can be any common source, but it is best to make your ground as short as possible. If you use the chassis as ground, make sure to scrape away any paint that could interfere with your connection.
The thermostat will typically have a probe that is to be positioned on the radiator somewhere. I like to put mine into the fins in the corner where the upper rad hose connects. This is the hottest area of the radiator, and a generally convenient spot. It should go without saying that the thermostat be located away from moisture, dirt and excessive heat. Now that you have everything wired up, the thermostat will need adjusting. Start conservatively with the fan coming on well below operating temperature, and then gradually increase the temperature setting until the fan maintains the proper (quarter gauge on the '86-'88 cars, half gauge on the 89+ cars) temperature. If you are unsure as to the accuracy of your stock temperature gauge, you absolutely must verify your readings with another source. Either an aftermarket temperature gauge (with it's sender installed before the thermostat) or a thermometer. The fan should turn on around 190 degrees or so in most cases as the thermostat is supposed to open around 177-183 degrees F. The fan should not fight the water-thermostat in maintaining temp, and should only run for a few seconds after the car is turned off (unless the car is very hot).
Sideways Maffia
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thanks, but i know how I'm wiring it, just wondering where to drill and tap in the thermostat sending unit into the cooling system. in order to monitor the proper area of the cooling system, and adjust fan control. I don't think those temp sensors that go in the fins are reliable enough...seems kinda cheap?!
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There are 2 schools of thought on where to put the sensor:
#1. Sensor in the engine. Nissan does this with all their FWD cars that all have e-fans. If the engine gets hot, turn the fans on. The flaw here is that if the engine is hot, it doesn't mean that the radiator is actually hot. Between putting the sensor next to the ECU's sensor or at the radiator outlet, it doesn't matter. The difference is 1* max.
#2. Sensor in the radiator or lower hose. This is where Nissan puts their overheat sensor on the SOHC cars. The idea is that the radiator fans should cool the radiator. If the radiator is cool (and the system is designed properly) the engine will always be fed with proper temp water. A sensor that goes into the water directly (a bung on the endtank or an adapter in the lower hose) is preferable. Those sensors that jam through the fins will work, but that mounting can be prone to fail.
I use a sensor in the stock location (in the engine). That's the cleanest way.
#1. Sensor in the engine. Nissan does this with all their FWD cars that all have e-fans. If the engine gets hot, turn the fans on. The flaw here is that if the engine is hot, it doesn't mean that the radiator is actually hot. Between putting the sensor next to the ECU's sensor or at the radiator outlet, it doesn't matter. The difference is 1* max.
#2. Sensor in the radiator or lower hose. This is where Nissan puts their overheat sensor on the SOHC cars. The idea is that the radiator fans should cool the radiator. If the radiator is cool (and the system is designed properly) the engine will always be fed with proper temp water. A sensor that goes into the water directly (a bung on the endtank or an adapter in the lower hose) is preferable. Those sensors that jam through the fins will work, but that mounting can be prone to fail.
I use a sensor in the stock location (in the engine). That's the cleanest way.
