Unless you changed the thermostat to a cooler one, some of the information being given out in this thread is wrong, with all due respect to other users. The engine is not going to run cooler than the thermostat temp, no matter what the fan is set at. You could turn the fan on at 100 for all it matters, if the thermostat isn't opened the fluid isn't going to flow. Why do you think vehicles run just fine at 30 degrees against 60 mph of wind....?

The Edge is returning the inferred coolant temp, calculated by the PCM, and its pretty close to the actual coolant temp.

The 2 main reasons for setting the fan correctly, imo:

1. You don't run the fan more than you need to which uses a slight amount of fuel due to the load it puts on the alternator, and creates extra, unwanted noise.

2. You don't use up the average MTBF rate of the fan and end up replacing it long before you normally would.

I'd say its time to stop the guessing game and data log the truck. That will tell you right off if its something like a loose ground wire impacting spark or fuel pressure, or something else.

 

Do not use the damn EDGE to read the temps. In 3-5 mins it says the motor is at operating temp. WRONG try 15 mins in 110 degree heat. I went through this man. Use a inferred thermometer and you will see. had my fans come on to early and mileage sucked I turned the fan on 10 degrees hotter than what i had. What do you know a increase or 2 mpg.

 

The Edge (or any other tool which pulls this data from the PCM) is measuring the temps inferred through the cylinder head temp sensor. The thermostat is a by-pass type. Fluid flows circularly through the system, without going to the radiator, until the thermostat opens. That's why the temp the PCM returns and what you are seeing at the radiator are two different things if the thermostat hasn't opened yet. The fans coming at too cool a temp will not cool the engine when the thermostat is closed --- they'll cool fluid in the radiator only because its not flowing into the engine until the thermostat opens (if not, then your thermostat is stuck partially open). Not understanding the theory and operation of a thermostat... or what the Edge is actually measuring seems to be missed here. If the Edge is measuring temps well in excess 195 and the radiator shows cold, then the thermostat is not opening at the proper temp and that needs to be looked at.

It's not much of a job to test it. Simply pull the thermostat, put it in pot of water with a thermometer in it. The thermostat should open after 192. If not, then replace it (they are cheap).

Optimally, electric fans should measure temps at the outlet site of the radiator, and be set about 10-15 degrees cooler than 192. This way, if the ambiant conditions are low enough for the radiator to cool the fluid without the fans coming on, you won't be powering them went not needed. Otherwise, by triggering temps before the fluid passes through the radiator, the fans will cool the system, but depending on ambient conditions it could be too cool. With temp probe placement at the outlet, they will only come on when truly needed. It prevents too much on cycling of the fan.

Your "15 mins at 110 degree heat" says nothing about fluid temps at the engine. It simply means that's how long it took your thermostat to open and start flowing --- its why you need to know what the engine is doing, because it'll help determine if the thermostat is functioning correctly. You need to know both the radiator temp and the actual inferred thems. Otherwise its just guess work.

BTW... I assume you mean an infrared thermometer, not a inferred. Inferred would assume a calculation - which is is what the PCM does, it doesn't have a coolent temp sensor, it infers the number based on cylinder heat temp and other data.

 

I know that after I installed my DC Controller and Lincoln fan, i had i similar problem. I had the fan set to come on way too early by accident (160 i think) and mileage seemed horrible. after re-adjusting it to correlate with the thermostat temp, 202, the truck ran much better and mileage improved. i know that the thermostat controls the truck temp, but that worked for me.

 

Ok if you ever had a nitro rc car you would know that you need the right mix and air to get the most power. So too rich poor consumption of fuel to lean and you run the risk of blowing it up. Than if you take the head temp vs block temp it will be different. So you need to take the temp at the core vs reading away from the core. All I am trying to do is help the guy get better mpg. His motor is not getting to operational temp which therefore is causing crappy fuel milage. So have the fans come on right around 190 and 200 should get better mpgs hopefully.

 

the thermostat will not open if the fans are over cooling.

theoretically you could go in and out of "normal" range but you would have to have some super strong fans to achieve that much of a temperature drop across the 32" wide radiator, you'd probably need an ambient temperature of 0* F and about 20,000 CFMs