So I have a 1999 Mercury Grand Marquis I've been a fan of the Scotty Kilmer Channel for at least a few years now recently I have bought a 1999 Mercury Grand Marquis and I put a lot of work into it however it seems to have a really big issue I live in Galveston Texas and obviously people from Texas no it's been pretty hot the last few days so recently I've been trying to turn on my AC but every time I do my car seems to overheat I've replaced the radiator hose the coolant reservoir and a few fuses I don't know what else could be the issue the Sam seems to kick on as long as I don't try to turn on the climate control once I turn on the climate control the fan stops working until after I let the car cool down for an hour so what could be the problem I don't want to go to a mechanic cuz I've been charged thousands of dollars and have been screwed over with my last car so I'm really just trying to get this issue fixed myself considering I use this car everyday for work thank you so much for taking time to read this and I hope that you can help me
Sounds like you have the electric fan. It should run on high all the time when Max AC is selected. If regular AC is selected, the fan won't turn on until the car reaches operating temperature and will cycle on/off based on operating temp.
On the fan shroud you should see built into it an electronic module with wires that go to the fan and wires that go back to the computer/hvac controls. These modules are known for failing especially given the age of your car. You pretty much just buy a new fan assembly which is very easy to replace yourself.
That may not be your exact problem, but from my experience with owning these cars that is where I would start if the fan isn't running when it should be as that module is common, well known failure point for the fan.
Alternatively, if you don't want to spend the money for a new assembly, you can get these for cheap at some of the you-pull-it salvage yards which I've also done.
You need a new radiator, not just radiator hose. And while you have it apart, put in a new water pump and t-stat
@gmcdiy The person you are responding to has not been active here for 3 years and is unlikely to see your comment.