What temp would you set a electric fan that has the temp probe on the thermostat housing ?

same as the thermostat value ? a little bit under ? a little bit over ?

thanks for your input

Maybe 3 degrees over roughly. You don't want it coming on for no good reason

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05 CRD: H.D.S2 stat,WW Ironrock trilink&LCA's, OX rear,ARB front, 4.10's, ARB bumper, Suncoast,OME 3.5, JBA UCA,rock rails, Moabs&265/75 Duratracs, GDE tunes ,FFD fan,ARP's, 2 micron fuel, new valves,sasquatch battery tray & grid heater, tensioner relocated
Mech fan, VH & AC delete

If you are using a 195F thermostat, I would set the fan to come on at about 200F.

Are you using this electric fan to replace the engine driven fan?
Are you still using the electric fan in front of the AC condenser?

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U.S. Army Retired

I'm presently using 203F thermostat in a HDS model 001

I replaced the engine driven unit for a Flex-a-lite Black Magic 15" electric fan and I'm using a Derale performance high amperage adjustable single electric fan controller. Turn-off temperatures are preset at 10°F below turn-on temperatures and it has a AC override circuit included.

How are you liking that controller? The flexalite one I use works fine, but if it ever fails your high amp one sounds interesting

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05 CRD: H.D.S2 stat,WW Ironrock trilink&LCA's, OX rear,ARB front, 4.10's, ARB bumper, Suncoast,OME 3.5, JBA UCA,rock rails, Moabs&265/75 Duratracs, GDE tunes ,FFD fan,ARP's, 2 micron fuel, new valves,sasquatch battery tray & grid heater, tensioner relocated
Mech fan, VH & AC delete

Very good product, the one that come with the flex a lite fan was the type you put between the fins of the rad and I didn't like it !

That's exactly what I currently have on my jeep (I got a 190F stant though), but I used zip ties to secure the probe on the radiator since I messed up a different radiator with the probe inserted through the fins. I also got a thermostat probe for the hds thermostat that I yet have to install, and you setting it from the start is a good choice imo.

I'm thinking out loud: setting the fan to start at your convenient temperature will take some trial and error attempts, based on your observations. I know that flexalite controller has a small adjustment screw, don't remember the low and high setting but I'd start with setting it in the middle. Then I'd look when the fan starts and observe the temperature with an obd2 scanner or torque pro. Then you can fine tune it till it fits your needs.

I do not know when the thermostat opens (usually its about 20F below the thermostat value, which would be 183F), a 203F thermostat should be fully opened at 203F if I remember correctly, so if the off for the controller is 10F lower than the start, you should set the on for controller at least at the (opening thermostat temp) + 10F. Otherwise your fan will never stop once it starts and the engine doesn't cool off under thermostat opening temperature, which in the summer time will probably not drop that low no matter what you do.

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2005 kj CRD, samco, suncoast tc, provent, Kennedy lift pump, GDE ECO full torque, 2nd gen filter head, 245/70/16 a/t tires, mopar light bar, fumoto oil valve, OEM Skid Plates, ARB Front bumper and HD OME, tru cool LPD47391 40k GVW tranny cooler (stock cooler delete), FF Dynamics e-fan and shroud, rocker arms replaced, HDS2 190F thermostat.

My thermostat is opening exactly @ 203F when I monitor it with the torque pro app, it is obviously not fully open. I will try to set the controller a little bit over and see, my controller goes from 150F to 240F.

I'm thinking about setting a led so I know when the fan is working, I also have the option of a ignition on switch to run the fan from inside the cab.

I gess there is no magic number , more like trial and error

thanks for your input !

What I have found in testing mine is that the HDS tstat can overshoot up to 96-97C(205-207F) and then once the cold fluid from the radiator comes through the motor it drops back below to like 93C(199F) and then settles at 95C(203F). This is here in the mountains so its usually while climbing a hill that I see this.

I am using an custom setup with a two speed Derale electric fan connected to the A/C fan wiring harness and currently have it setup in the tune to turn on low speed at 98C(208F) and high speed at 99C(210F).

The issue with having the HDS with a 203F tstat is that if you are in a high load/extreme cooling situation you dont have a ton of buffer before fueling starts to cut so you dont want to allow the radiator fan to come on too late after the the engine starts to heat up past the t-stat temp. If you are not running the fan, it will heat up under higher loads(not just towing).

Also, Just an FYI, on the stock tuning the A/C fan is set to trigger low at 96.5C(205.7F) and high at 107C(225F), so its possible that in normal driving situations the A/C fan can trigger low speed with the 203F tstat if overshoots a little bit, which I have observed it doing. It seems the T-stat has a small delay in opening and/or the time it takes to get the cold fluid from the radiator through the block is long enough to allow it to go a few degrees over 203. There is a time delay on the A/C fan turning off, so if you do hit 96.5C it will turn on and run for a minute or two before shutting back off, regardless of coolant temp.

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2006 CRD - GTB2056 turbo by Dieselguy86, Eco Trans Tune, Lift Pump, Week's, HDS Tstat, Racor Filter, ARP's, OME 790's+Top Plate, JBA 2.5", JBA UCA, Moab's+265/75R16, ARB Bull Bar, 4.10's, TrueTracs