LS3: Apparently I need three coolant sensors

[ModernMuseum]

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?

[parsonsj]

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.

[79 Camaro]

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

[parsonsj]

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.

[Z06vette]

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.

[Mkelcy]

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-truck-conversions/3316-3-wire-temperature-sensor.html

[marks914]

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

[79 Camaro]

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.

[Chris442]

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.

[camcojb]

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.

[BonzoHansen]

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.that's pretty wild I did not know that. Only corvettes get that?

[Chris442]

that's pretty wild I did not know that. Only corvettes get that?

That's all I know about, for sure. I can say for certain that G8s, GTOs and new Camaros don't have it, though. Based on what's available in HPTuners, I'd guess it could be made to work with any of those computers, but I've never tried it.

It's been working great on the Camaro for the last 3 years and 15k+ for me. With the big Ron Davis and dual Spals, you rarely hear the fans run, since they're almost never at 100%.

[BonzoHansen]

That's all I know about, for sure. I can say for certain that G8s, GTOs and new Camaros don't have it, though. Based on what's available in HPTuners, I'd guess it could be made to work with any of those computers, but I've never tried it.

It's been working great on the Camaro for the last 3 years and 15k+ for me. With the big Ron Davis and dual Spals, you rarely hear the fans run, since they're almost never at 100%.

I have a DCC in my car and even with one of the fan motors having a bad bearing I still don't hear them. At idle on a 90* day they hover around 6-7 volts. I had no idea GM was using PWM.

[68ZClone]

Any reason the fan controller from Dakota Digital would not work?

http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=641/prd641.htm

[ModernMuseum]

Ok, in tying up some loose ends, I decided to just use the sending unit that came with the Dakota Digital and install the sensor in the radiator line.

Do I install it in the large 1.5" line or the smaller 1.25" line? I almost pulled the plug on a 38mm adapter (1.5"), but then remembered that I don't know which line I have to install it in!


Here's a decently priced one for $25.

[ModernMuseum]

I guess I should clarify...should it be the upper or lower radiator hose?

[camcojb]

I guess I should clarify...should it be the upper or lower radiator hose?

the upper hose is water returning from the engine to the radiator and would be the one to use.

[ModernMuseum]

That's what I thought. Thanks Jody.