Cooling fan specs

According to GM specs, the thermostat opens @ 190 F. I would check to see if the thermostat is stuck by feeling both radiator hoses are warm hot when it's at that temperature. Check to see there are no air bubbles that would cause different measurements (Classic symptoms). Verify current consumption of fan on the relay and on the fan motor. Use the scanner to activate it. This is what I would…

That's my experience with this era of GM LS engines. Last one I had customer with identical complaint I replaced thermostat and did a coolant flush. Personally I think the gauge is getting a bit “sloppy” for lack of a better term. My ECT never got above 200 as well. I do not know what temp the fan should kick on at. Check cooling system description and operation in SI, should be in there.

Every single gm vehicle I have ever seen with an electric cooling fan turns on at 220. If it truly does get to 210 while cruising, it probably needs a thermostat.

I think the exception is some late models with electric thermostat , those can run at 240 at idle before fan operation. What do you think?

The only customer complaint is the gauge operation operation. This vehicle was in another shop and they replaced the water pump, radiator, and thermostat. I need a reference point for when cooling fans are supposed to come on. I could not find it in any service information .

Really there isn't any specific info like that. Good to know those parts were replaced. The only reference you have is the resistance chart of the temp sensor. There have been cases where the sensor after some years of usage has become “sleepy” which does not give an exact precise value. I would do a resistance test doing a bench test in hot water and compare it to the chart. Now I can't stress…

I would be willing to bet that they installed a Motorad, or CST thermostat. If the gauge was reading lower before, either their old thermostat was opening too early, or the replacement is opening too late. If it were my customer, I would dvise them that 210 is normal, but if they wanted, we could install a Stant, or oe thermostat, and see if that makes a difference.

These trucks are notorious for gauges being inaccurate when the stepper motors in the cluster start to fail (most common on gas and coolant temp I'm guessing from them being so dynamic in operation all the time) do a cluster needle sweep from scan tool and see if they line up with the others or off a little this may be your problem

One way to get the turn on temp is to watch the “request” but then you would need to compare it to another truck or two. If the request does not turn to “yes” until 220 that will be where the PCM wants it on, and not before. Then all that's left is try comparing the “actual” temp to what data stream shows to make sure coolant temp sensor is reading correctly.

220 sounds about right to me for fan turn on, although I don't have the actual spec. And just shy of 210 on the gauge is where I see most of these read. However, the instrument reading is essentially a “false” reading. If you look in the Instrument Cluster PIDs you will see “actual temp” and “displayed temp. "They” decided at some point that too many people were upset by the normal fluctuations…

Ran into this a week or so ago on the same type vehicle another tech had. He replaced the intake I believe for unrelated problem. Noticed fans were not cumming on when trying to burp the system . I read the same spec in shop key. We could command the fans on fine with scan tool. After letting it run for a bit ect read 220f fans kick on. Let the vehicle go not

Jo, After fighting Multiple 6.0, with customers who monitor gauges closely, and complain of a Higher than “used to be” temp, The problem was air. Other shops had replaced everything, the issue was the bleed hose going to the pass. side of the radiator and the tubes coming off of the heads. With an obstruction in any of these, it is impossible to get all the air out. How did I figure it out…

Thank you Mike & everyone that helped. Last night we performed a block test and temperature testing with an infra-red thermometer. Everything seemed normal. I'm sure In the near future we will have another similar vehicle to do comparison testing. We'll post if anything new shows up.

As several others have pointed out, the turn on temperature is right at 220 degrees, although I've had them be off a few degrees either way. But that has been the standard for GM vehicles ( most of them) for many years. Duane has this exactly correct. There is nothing wrong with the truck, the customer is a bit anal is all. Gauges are more of a smart ‘idiot light’ than anything else.

I run into this all the time, the actual low speed kick on temp is either 220 or 225, I cant recall. They rely on convective cooling and if the radiator is dirty at all, inside or out, it becomes an issue. I have used HpTuners in the past to change the fan logic to extend the life of radiators. The gauge will read 210 anywhere between 190 and 220. Only at 225ish will the gauge start to move up…

Important: The right and left cooling fan connectors are interchangeable. When servicing the fans be sure that the connectors are plugged into the correct fan. The PCM commands the low speed cooling fans ON under the following conditions: * Engine coolant temperature exceeds approximately 104.25°C (220°F). * A/C refrigerant pressure exceeds 1447 kPa (210 psi). * After the vehicle is shut OFF if…