Ultimate LS Systems 700xx information
I've just run across these.
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There's no CEL wire in the FITech wiring harness accessory bundle and I don't see any other output that might serve that function. Is there a way to illuminate a standalone check engine light (or preferably, the built in icon for a VHX Dakota Digital dash) in the event of a system error?
I'm getting around to wiring up my 70050 for my iron LS3, so I'll probably have to tap into this knowledge base more than once I'm sure, so bear with this newbie.
I noticed in this post that wiring for dual fans is with 3 relays going by the schematic that Paul has posted. My question is I have purchased 2 ground activated relay kits from Painless.
https://www.jegs.com/i/Painless-Performance-Products/764/30109/10002/-1
Are the 2 kits I have okay to use to control the fans or do I need to purchase another kit? Or is there another option to use.
Paul or anyone that can help is much appreciated.
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Single relays like these will control one-or two fans only as on or off. If this is what you want, I would suggest one relay per fan.
You could have one fan come on with the first ECM fan output and have the second fan come on with the second ECM fan output.
However, when the fans run, they'll be at full speed.
The three relay setup will run both fans at half speed then full speed. I do not know of any company that offers this setup already wired. The relay you posted will not do this.
Forget about using a relay to control the fan, I highly suggest using a PWM Fan controller instead. The benefit of PWM Fan control is when it turns on the fan it gradually ramps up the speed to prevent a sudden current draw from the alternator as the current draw is ramped up gradually. It will vary the speed of the fan or fans based on the sensor. The helps prolong the life of the fan. Also it will run the fan after the car is turned off to help cool off the rad and engine and prevent heat soak. I have the one below installed in my car and I swear by it.
SodaPop, that's a stand alone fan controller. The fan on/off temps can't be adjusted. Using the low/high speed fan triggers from the Fitech ECM allows user settable fan run temps-without an additional temp sensor in the other head. Some larger CFM fans draw 25 amps so two of these would be needed. It's kinda pricey at $175.00.
With proper sized fusing and wiring, nobody should have issues with a fan starting at full power.
The two speed three relay series/parallel F-Body setup controlled by the Fitech ECM starts the fans at low speed then it goes to high speed if needed which reduces the inrush current.
Not pricey at all and well worth the benefits. I swear by it. All modern cars use PWM Fan controls. You can adjust the on and off times as they have other different temps sensors. A quality fan draws only 9 to 18 amps depending on size, so the 40 amps is able enough and because they gradually increase and decrease the fan speeds, the 40 amps is fine. Also your setup will not run the fans after the car is shut down to help with heat soak. I find it funny how people will spend a tone of money on engine and engine upgrades and cheap out on a very important function such as cooling......
Guys, thanks to both for your responses. Since I already have the ground activated relays I think I'll use them for now.
SodaPop any additional info on wiring with the Northern unit would be helpful for a down the road project.
Another question I have that's not related to cooling but with Tach wiring. My stock 69 Camaro tach runs off a 12v signal and the Fitech ecm only has a 5v signal to run off of. I know that Dakota Digital has a module to convert the signal but does anyone know of a less expensive fix? Down the road DD in dash speedo and tach are on my list just not right now.
Thanks again
Simon
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Quote from SodaPop on August 8, 2021, 11:12 amNot pricey at all and well worth the benefits. I swear by it. All modern cars use PWM Fan controls. You can adjust the on and off times as they have other different temps sensors. A quality fan draws only 9 to 18 amps depending on size, so the 40 amps is able enough and because they gradually increase and decrease the fan speeds, the 40 amps is fine. Also your setup will not run the fans after the car is shut down to help with heat soak. I find it funny how people will spend a tone of money on engine and engine upgrades and cheap out on a very important function such as cooling......
I consider $175 expensive when the EFI system already has user programmable fan control outputs. For delay shutdown, Hella has an adjustable plug in relay, I use it to keep my water pump running for 90 seconds.
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LS69er, use the diagram that comes with the PWM controller for hooking up the system. You just would not use the fan control on the fitech. You should be fine with just using the relays if they come on half power at first. For me personally I dont like the sudden current spike draw on the alternator even with half power, I prefer gradual increase in fan speed which is less harsh on the alternator and fan. Also I like the PWM adjusting the speed of the fan based on temp, which makes for a quieter fan noise.
Paul Bell thanks for the tip of the of the relay, I didn't know they existed, and can come in handy.
My curious question for both of you would be, since you are running a LS motor, are you not better off using the complete system from GM such as the intake, injectors,sensors, ECU, etc? Just curious, as that is what people here in Canada do. It runs very well based on taking to people.