Well summer is here and now when I end up sitting in a little traffic I get to watch in horror as the temperature needle climbs toward red.

I know the culprit is the fan not coming on, and I called my local NAPA where they always seem to know what they’re doing to order a coolant fan switch:

http://napaonline.com/Catalog/CatalogItemDetail.aspx?R=MPEFS110SB_0306485468

I mentioned to the guy my fan never comes on and he said I would need a coolant temperature sensor instead. He said it is near where the upper hose connects to the motor.

Really? A fan switch isn’t the part that switches on the fan?

If I’m wrong about the fan switch being what switches on the fan, than what does that do?

You should add your car to your profile. What year is it? What engine?


- Your not-so-local, untrained, uncertified, backyard mechanic. But my @!#$ runs

I'll be happy to share what I know.
I believe on 4 cyl. OHC & OHV engines the temp switch is on the heads facing the drivers side wheel well. Brazil heads are under the distributor and a bit harder to see at first glance. The 6 cyl.'s I'm not any help with. I bypassed the temp switch and set a toggle switch up on the dash in my wagon - been very happy with it as I can turn the fan on at stop lights or when moving in slow traffic or in parking lots.
The temp coolant switch feeds to a relay that turns on and off the fan - you might want to make sure the relay is OK so you don't waste money on what is already a good switch. Those relays are in different places unfortunately. On the 1.8 Brazil engines, they are next to the battery above the wheelwell. Not sure of the locations on the OHV, I had simply rigged my toggle directly to the fan and added a mechanical temp gauge at that time.
Maybe others can finish the story, be nice to know!! :-)



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I guess I should've mentioned I have the 1.8

Well, Orlen, you seem to have the same info as the guy at NAPA, so that's what I'll go with.

I thought of the toggle switch, but I would rather have it work the way the factory set it up, and the part is cheap.

I would start by rigging up 12V from the battery to fan and see if the fan is good and then work your way back to the relay which like Orlen says is on the drivers side fender wall.

Oppppppssss......

John is 100% right there Wayne! Sure is nice to have my back covered!!

Those fan motors are prone to go.....completely forgot!

Got a couple of spares from the local yard just for that reason. Do check the fan and work back !! If fan is toasty, try to get one from the yard, used fans run around $35 if that much while one from the Zone will set ya back around $100.....OUCH!



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Relay location.....







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Wayne it is pretty simple to test I believe the switch is on the neck of the radiator fill/thermostat housing and has a green single lead plugged into it just unplug and put the green wire to ground the fan should turn on this will check the relay/fan .Let the car idle the fan should kick on when the temp gauge reads about 220 the switch will close ( you can check with a dvm or any device you can read continuity with .Set the volt meter to ohms lowest scale and one end on the spot the green wire plugged into the other to ground if you have a closed circuit or short anything but ol or open loop on the meter then the switch is good if it never closes bad switch the car may need to idle 15-20 minutes depending on tempature the green wire needs to be put back on for the second test .Good luck
k923


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the other thing i would check is if the thermostat housing is full of coolant when you remove the cover the switch uses the coolant as a path to ground to activate the fans I know its basic but its real simple to miss.k923


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Just for future reference in case the above parts become scarce

..and all I was gonna do was replace one simple part, now I have a project on my hands

love that pic orlen, mine has the washer bottle in front of the strut tower, but my relay might be nearby, I'll have to look.

I've had more fan motors fail than anything else.
dennis

Everyone has pointed you in the right direction, my fan motor was the culprit when my fan quit working so good luck with it

My first Hawk, it wasn't the fan motor, it was a switch.

What I'm having a hard time wrapping my head around is the temperature gauge works fine, it stays between 180 & 220 unless it's hot out and I sit in traffic. Then it just keeps going up and I never hear/feel the fan turn on. One of these days that is gonna bite me in the ass, so I want to fix it.

Because the temperature gauge works fine, that's why I have a hard time thinking it could be the temp sensor (not that I actually have a clue what I'm doing).

I went out and looked at the car, found the connector near the thermostat, and the temp sensor under the distributor cap.

Now I gotta go back and read this stuff to learn how to test it.

This is why I love this site, so much info from so many who know willing to teach a no-nothing like me.

Wayne-

On my 84 OHC Turbo, my fan relay used to be where Orlen pictures his. On the turbo car they are on the same bracket with the turbo timer.

Does your car have AC? If so, turn it on and check for fan operation. The fan should be commanded on by the AC. If no AC, I agree with the recommended approach, start backwards from fan (direct power).

It sounds like you have figured out that the sensor on the head is for the ip gauge and the one on the T-stat neck is for the fan. Thats a fun one to learn

I can send you the diagnostic page from the shop manual if you would like.

Well now it makes sense that the temp gauge works fine, but fan still doesn't come on.

OK, so now I know not to look at that one on the head, and I can look at the one on the T-stat neck.

So, Paul, what you're saying is if I turn on the AC (not that it works, but I figure that shouldn't matter as the fan won't know I'm out of freon), the fan will run even if it's right after I start the car? Hope so, since that will tell me if it's the fan motor or not, then narrow it to the relay and sensor on the thermo neck.

At least that test I can do first thing in the morning before I go to work.

Wayne, I had a few minutes to tinker around in the garage myself today.

Just for kicks I popped up the hood on the Pontiac. Disconnected the connector at the T-Stat with just 1 wire. It was Green with either a white or black stripe - but it definitely has only 1 wire going to that sensor. I took my VOM wire and shorted it directly to the Neg terminal of the battery and the fan did light off. The ignition has to be in the "run" position. If you touch the battery rather quick several times, you can hear that fan relay clicking too.
Gave me a nifty idea to splice in a toggle switch at the dash and ground it out - that way I can cut the fan in and out as I would like to, but still have the sensor working if I happen to get absent minded - as I do sometimes....LoL

This would definitely eliminate your fan and relay if it does cut on!!


Like you I was wondering if the fan would cut on if the A/C was out of freon. Amazingly, my system is still fuctioning, so I wasn't any help to you there.



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I think we now have the step one and step 2 of the diagnostic steps covered - Thanks Orlen

You probably have a bad cts. There are two sensors on jbodys one for the gauge and one for the ecu which controls the fan. The cts for the ecu is two wires, yellow and brown I believe.




On the inside my car looks like a fighter jet.

Your help has been invaluable along the way Paul!!

The wonderful folks on here , and the forum itself are always teaching me all kinds of things!!

You can learn a lot from others experiences!!



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Started the car this morning, turned on the AC and lifted the hood.

Fan spinning just fine, so I guess that leaves the sensor at the thermostat neck, I'll go pick that up today.

Now this makes me wonder, for those of us with AC, does that mean we will never need a toggle switch as we can just turn on the AC if the fan doesn't come on by itself?

Of course this would still put a big load on the motor, but would it really keep me from overheating?

Thank you to everyone for their input--we rock!

Since your A/C isn't working, you can simply disconnect the wire going to your A/C compressor clutch. I'm thinking it is green. Then you can use the A/C control as a fan switch anytime you need to!! :-)

Glad to hear you are getting things figured out!!


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Found that wonderful wire (actually, I knew exactly where that AC wire was).

It's kinda like a rubber boot with a household plug style connection, I just squeezed a little and pulled it out. Between this being disconnected and the fact that I don't have the AC belt on the car, it made my heater control a factory installed toggle switch for the fan.

Was out yesterday in the heat and in traffic, slid the switch to AC and enjoyed watching my temp gauge stay in the normal range.

I'm still gonna install the temp sensor at the t-stat neck so it comes on by itself, but what a lovely fix--thank you all!

AC will work fine as a bypass switch as long as your relay doesn't blow. I have a direct wired switch in my car. I was in Maine one year, I live in pa, drove there for 3 days and my car kept overheating and I didn't know why. Only overheated when sitting still. Here it was the relay it melted. Guess what no part stores in 50 miles had a replacement. So I hot wired it to the battery with an online fuse do I could pull the fuse when parked. Got home got another relay and just wired a switch in as backup. My car has never had working AC in 5 years. Last year I gutted like 100lbs of AC crap.




On the inside my car looks like a fighter jet.

Went to NAPA today to order the sensor and a few other things. Just before going in I decided to lift the hood to get a look at the wires going into the sensor.

There are two sensors plugged into the thermostat neck--uh, which one trips the fan?