Your Hummer H1‘s radiator fan has one of the most important jobs on the vehicle. It is the last line of defense between you and an overheating engine. If the radiator fan is not working, it’s a serious problem.
Just because the radiator fan is not on does not mean that it is not working. They are designed to only run when needed. If your H1 is running hot, and the fan is not running we’ve laid out the most common causes of this issue below.
Hummer H1 Radiator Fan Not Working Causes
There are a few simple reasons that the fan would not be cycling on. Although the fan itself can go bad, that’s definitely not the place to start a diagnosis.
Here are the most common reasons that your radiator fan does not turn on:
Before poking your hands around your fan, make sure to treat it like it still could come on, and and keep your hands out of its path.
Wiring
The first thing that you would want to do is locate the fuse for your H1’s radiator fan and make sure that it hasn’t blown. If it is blown, replacing the fuse will only solve the problem for a very limited period of time. Unless the wiring issue is fixed, the fuse will blow again.
The wiring harness itself can go bad. Your author has personally had a shredded tire completely pull the fan wiring out of his vehicle. It can happen. The fan wiring is some of the more vulnerable wiring in your H1.
You can test the voltage going from the fan relay to the fan itself. If it is getting 12+ volts, the fan should be coming on. But if it’s not, which means the fan has gone bad.
This video from Ratchets and Wrenches is a phenomenal resource on how to properly diagnose a wiring problem.
Engine Temp Sensor
Your engine temperature sensor is responsible for relaying your engine temp to the ECU. Once the temp gets so hot, the ECU commands the radiator fan to come on. If your H1 has a bad engine temp sensor the radiator fan won’t know to come on, because the ECU won’t know how hot the engine is.
You’ll need to locate and test the engine temp sensor. Depending on the model year and engine, the location varies. If it does end up being this sensor, they are very affordable.
Low Coolant
If the engine coolant level isn’t high enough to keep pressure in the engine it will run hot. But, there won’t be enough coolant to reach the temperature sensor. Without the coolant hitting the sensor, the temp reading will be significantly lower than the actual engine temp. Your H1’s radiator fan will not kick on.
If you do have low coolant, don’t fill it up until the engine has cooled off. Adding coolant to a radiator dry enough not to trigger the engine temp sensor can cause problems from drastic temperature change. Let it cool down first.
Fan Clutch
Like any other clutch, a fan clutch will wear out over time. If everything else seems on the up and up, the springs in the fan clutch have worn past the point of proper function and can no longer do their job.
Conclusion
There are many reasons why your Hummer H1’s radiator fan is not working. Of all the ones listed above, start with the coolant level, then check the fuse. After that, the order isn’t so important. But, you don’t want to miss the easy fixes before you start testing wiring.
If there is anything that you would like to add, please leave a comment below. Good luck!!