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94 Mercury Sable - Fan Comes on, Car won't start

In my Sable, when I turn the key just prior to trying to start the engine (I’m not sure what that position is called, but I’m sure ya’ll do!) sometimes the fan by the radiator starts. It’s blowing hard enough to move my hair from a slight lean by the engine.

When it doesn’t start blowing, the car will start. But every time I hear it, it won’t start. I know the fan is supposed to kick in when the engine heats up a bit, but this happens on a 65 degree day after it’s been sitting for 8+ hours.

Anyone got any thoughts? Any way to diagnose the problem or work around it? So far kicking the tire in anger is the only thing I’ve tried and it’s not working.

Not sure how Sables are wired but suspect it is similar to most cars.
There’s a sensor that determines the car’s temperature. I bet it is telling the car it is overheating so it is having a hard time starting. Your temperature sensor is probably bad.

Most cars have a limp mode where, if you start it enough times, it overrides that fault and starts.
That’s not a fix but certainly another clue that points towards the temperature sensor.

I am assuming that the starter is at least working when the trouble happens and the engine just won’t fire up when cranking it over. The trouble might be due to a faulty chassis ground so it might help to clean the chassis and engine grounds. Try spraying some starter fluid into the intake to see if that helps get the engine fired up. If that doesn’t work then check the ignition system and see if it is working alright.

@RemcoW - Thanks! I guess that’ll (temperature sensor) be the first thing I try tomorrow. Is that something that would be on again and off again? It died at work Monday (it’s done this same thing before though) and now it’s Thursday and it’s still just sitting there.
To get it to limp home, would you recommend actually trying to start the engine or just turning on the auxiliary power? I’d much rather have it dead and at home than dead at work.

@Cougar - As it relates to the starter, and keep in mind I’m an absolute newbie, but the only thing that I and one other person noticed that’s different from when it starts and when it doesn’t is the radiator fan kicking on. When it starts, it starts right up. But it’s something I’ll look into.

Just to clarify: when it doesn’t start, does the starter turn the car over but it doesn’t start?
If the starter doesn’t do anything when you turn the key, it most likely isn’t that temperature sensor. I assumed it was turning over and not starting.

@RemcoW Yeah it’s turning over but not starting, just as you suspected.

Ah, In that case it definitely isn’t the starter.
That radiator blowing is the clue that points to a temp sensor but just to make sure:
When the fan blows, you don’t have your cabin temperature control set to “AC” or “defrost”, right? The cabin temperature control is off?

Select a vent position. Some fords will start with the engine fan going when a defrost mode is selected. Only Ford knows why.

@RemcoW Yup. It’s set to ‘Off’. I think you’re on the right track. Everyone I’ve had look at it (shadetrees) ignores the fact that the fan is blowing. I’m not a car guy, but I have a scientific mind so I notice patterns and consistencies and that’s definitely the one constant every time it doesn’t start.
The battery died now since everyone ignored the fan, but I’m going to replace the temp sensor ASAP and get myself back up and running. Thanks a lot!!

@pleasedodgecan2 That’s insane! Maybe I’ll give that a try once my battery is replenished so that I can drive myself to the parts store!

@RemcoW After a little more research, I’m finding a few different temperature sensors. But I’m assuming this is the coolant temperature sensor?

Thats right. It should be on top drivers side of the engine

The sensor you are looking for is the one used for the engine control module so it knows what the coolant temp is. There is also a different one used for the dash gauge. That one usually has a sigle wire tied to it while the the one for the ECM may have two wires.

@Cougar Still researching. Is this:

what I’m looking for? I’ve seen some that say it controls the dash gauge, but best I can tell this one is for the ECM. This is all new to me and I’m trying to learn, so I really appreciate everyone’s help!

Wish I could post a picture. The temp sensor at your link is a single wire. You want the 2 wire. One wire is green with a red stripe, the other is gray with red stripe.

You’ll find it near the top drivers side of the engine.

Does this help?

It took me a little while to get it handled, but the other day I decided to just bike to AutoZone after work and take care of the sensor. I got the sensor, didn’t have a good wrench or socket with me so I tried just unplugging the old one and seeing if it would start. It did. So I drove it home (about 2 miles) where I found a good wrench and replaced it. The car started right up and I drove it around for about an hour. I drove regularly for a day or two and had no issues.

Then this morning I went out to start it for work and it didn’t start so I turned it to listen for the fan and it was on.
Any thoughts?
The only thing that’s changed since it last drove was that it has been raining. I don’t know that that has anything to do with it, but from what I’ve seen over the years, ever little detail could matter so I like to be thorough.

Thanks to everyone for their help, though! For a few days, I wore my Snoopy bandage on my scraped knuckle from a wrench slip from replacing the sensor with an obscene amount of pride and I couldn’t have done that without you all!