LS3: Apparently I need three coolant sensors
 

Engine: LS3
Radiator: from Prodigy Customs
Gauges: Dakota Digital Series III

To monitor and make all the systems work correctly, it appears that I need three sensors to make all this happen: one sensor for the ECU, one for the fan controller and one for the Dakota Digital gauges.

After some research, it appears that all three use different signals and there is no way to piggy back or combine any of them.

As far as I know, the LS3 only has two locations for sensors, which is at the back of each cylinder head. Am I going to have to tap into the water pump for another sensor? What is your recommendation?

II Much had 3 coolant sensors too, though my FAST XFI could have shared the Auto Meter gauge sensor (I didn't learn that until later). I tapped the water pump casting without any problem.

I'd double check the ECU and gauges... if they both use 2 wire sensors, I'd bet they can be shared. I don't know anything about the radiator.

You could use the ecu to turn on the fans. Speartech did that for me.

For sure. I've got a 69 Camaro here right now that works that way. Most ECUs have support for that.

I would add that I like external fan controllers, especially if they support PWM-based speeds where the fans run a slower speed to keep the temp right where it's programmed. Most ECUs just have binary support: either the fan is on or off.

I used the stock 02 camaro ECU to run both the fans & turn on one fan when the AC is turned on. It depends on which computer you have, might not work on your setup.

There's also a two output temperature sender from an LS1 Camaro that may work. This was the first link I found with part numbers: http://www.ls1truck.com/forums/lsx-t...re-sensor.html

Yes for any setup you probably will have to run 3 senders, each has their own ohms range. But 2 should be in the engione, one in the radiator (fans)
Mark

The other solution is to weld a pipe thread bung into the radiator assuming it's aluminum. I did that on one of my LS swaps. Placed it down near the bottom of the tank on the drivers side. Welding shop charged me about $25 for some pretty tig welding.

If you want to run those three things, you'll need 3 senders. It's worth noting that the ECU is capable of PWM fan control; all Corvettes have had it since 05. I have this set up with an LS7 in a '68 Camaro. I also use an A/C pressure sensor for the computer to run the fans for that. Without going into too much detail, you'd need the PWM module from a Corvette to make it work and be able to set, or have somebody set, the computer to work it.

As to the third location for a sender, I used the block drain above the starter, but haven't had great success getting accurate readings. It's good until the engine is warm, then it keeps going an extra 20-30* from the ambient heat down there. It could be that the adapter I've used for the sender has it too far out of the water flow to read right, but I haven't tried to fix it yet. Basically buyer beware on using there to read.

Another option I've see is drilling and tapping the water pump by the thermostat, IIRC. I've never tried it, so no first hand experience there.

I have never needed three senders for the three things. Every ECU I've used has a fan control built in, and it uses the same coolant temp sender for the ECU and for determining when to ground the fan relay, controlling the fan.

If your computer doesn't have fan control then the above ideas will work fine.