So I recently bought a 1987 5.0L V8 Firebird Formula. It's a single fan carbeurated car. The car was in pretty rough shape and I've been fixing her up for awhile now. One of my main issues since I have gotten the car to run again is that the fan will not switch on once the engine gets up to 220-240ish. The fan does come on when I run the AC though, and the car cools back down to 195. So far I've replaced the thermostat, the coolant temp sensor, and the coolant temperature sending unit, which fixed my gauge, but not the fan. What else could be the problem? The only thing I can think of is to maybe replace fan switch? the only problem is, I don't know where that could be!

 

Normal operating temps are 200-220. Let the car warm up more,..... 195 is too cold for the fan to come on.

 

The fan switch is near the knock sensor, on the right side of the engine block.

 

Second the fan switch, if u can get to it. Before i went replacing it id try and borrow or buy a temp gun to make sure your temp guage is accurate. Point it at the thermostat housing neck to measure it. It could be it just not reaching operating temp for it to kick on.

 

It's interesting that you say this. I already own that laser gun thingie and my housing neck was reading quite a bit lower than my gauge. But seeing as I just replaced the coolant temp sending unit I assumed the gauge was accurate and something else was amiss. Also, the woman I bought the car from told me that the car overheats without the AC, which I can kind of collaborate bc I can see the temp gauge rapidly approaching the red without the fan running

 

When you say right side, you're referring to my right if I'm inside the car, right?

 

If the coolant isn't boiling over, maybe let it heat up to the temp on the laser gun instead of the temp Guage. If the fans kick on when the laser gun reaches 235 then u know the dash Guage is still off which to me is more likely. U can also test the gun on other things to check it's accuracy.

Not sure if u have the dual fan set up but the primary kicks on first at 235. The aux kicks on at 240 (I think? Can someone verify?) when the AC is turned on as long as it's charged. Its pressure based switch for the aux and won't work if the AC system is empty. My guess is the car was never overheating but due to the bad Guage she thought it was and was constantly running the AC.

Also, Then temp fan switch is on the passenger side

 

Alright, so I tried your experiment. I ignored the temperature on the gauge and relied on the temp gun. According to the temp gun, the thermostat housing neck got up to 235F, while my gauge read 260+. So I can conclude my gauge is in fact inaccurate but my fan still did not come on. I'm back at square one. Pics related.



Thermostat Housing Neck reading a temperature of 235F.





My temperature gauge reading as hot as it can at 260+

 

The base fan relay is controlled by the ECM and a redundant coolant fan switch (lower right hand rear above starter solenoid). The redundant fan switch should turn on at 232 ±°F (238°F for VIN E engines). The ECM is using the coolant temperature sensor (Top LH front of engine) and the fan pressure switch in the AC if you have AC. Since the ECM will turn on the fan relay when the coolant temp is above 222±°F, it appears that both sensor and switch may be bad or the ECM. The coolant temp sensor is also the source for the temperature gauge.

 

The coolant sensor should have 1254 ohms at 100°F and 54 ohms at 260°F if you want to test it. When you turn the key to start, the bulb test function of the ignition switch should cause the gauge to go to full hot as it jumpers the sensor to ground.

 

Replace the gauge sending unit. I say it's bad because your gauge reads 260+ and you didn't describe an overheat condition. ( FYI: Head coolant temps and intake coolant temps are NOT EQUAL ! )

Verify that the radiator cap is a stock rated 15lb cap. ( check spring inside too )

Run the car @ idle until the radiator cap opens and begins to allow boiling coolant back into the overflow.

Check gauge for accuracy.

Shut off the car.



The car will begin to overheat right after 240is and just before 260is with properly mixed coolant. Once the car reaches this temp you will KNOW what temp the coolant is at and will not need to depend on any measuring device other than your own eyes.

If the fan never came on during this check then - with the key turned to RUN - remove the coolant temp sensor plug from the fan switch and touch it to ground. You can do this hot ( be careull ! ) or once the engine cools down. If the fan kicks on then the sensor is suspect...... if the fan doesn't come on then the relay - or power/ground to the relay - is suspect.

 

Hopefully it's only the fan switch because I've just replaced my coolant temp sensor when I replaced the thermostat.

 

It seems like I've been trying to solve this problem a hundred different ways. My thermostat has been replaced, along with the coolant temp sensor attached to it. My radiator cap is brand new and has been tested and is holding pressure. My coolant temp sending unit to the gauge has also just been replaced. My fan will come on when I turn in the AC, although the AC hasn't worked in some years, so I suspect my relay is good. By the process of elimination, my last guess is that my fan switch isn't working. I've just gone under the car and detached the wiring and plan to replace it soon.





Passenger side of the vehicle, under the exauhst manifold. I believe that must be the fan switch. Correct me if I'm wrong.





Should I also replace the connector? It's old and brittle. A small piece of plastic broke off of it when I disconnected it from the fan switch.





Just another angle of the cone tie showing broken plastic. I don't think it will cause a bad connection, but is it worth replacing?

 

yea I would replace it, I actually just did this the other day, mine looked worse than yours, I might be mistaken but when you snip then end of that connector, if you touch it to ground and the fan should come on if its working.

 

How the hell did you get yours out?! I have the car on ramps and I'm trying to get it from the bottom but there's just no room to fit any tools! Should I come from the top? I feel like that looks even more restrictive.

 

Funny u ask me and another member just had this talk lol. Its not a fun job. I had to use a 22m socket and 22m open end wrench. Neither fit very well and just had tobuse which ever one turned it at the time. I had to use a screw driver to wedge the dip stick tube out of the way alittle. Once out it seemed to go back in easier but just took time. Please do it on a cool engine lol

 

Thank you. It took a good half hour but I was able to get it out eventually! Unfortunately, the fan still won't come on. I guess I just gotta give up and drop it off at the mechanic

 

BTW, you guys do this with the coolant empty?

 

A carb'd/tbi engine has no ECM fan control. You can put a million new stock fan switches back in, they will all turn on at the same temp... 238°F (± a few degrees tolerance).

The ONLY way the fan will come on at a lower temperature, aside from using the hvac controls, is with a fan switch that turns on at a lower temperature.

 

Hate to suggest this bc I am not one for throwing parts at a car but I got a bad coolant temp sensor once brand new. Did u ever test it with a multimeter like the other member suggested? If it's cheap enough is it worth buying/trying/returning? Just hate to see u bring it to the shop.

Also this is the primary, not the aux fan were talking about right? FYI I don't think the fan switch controls the primary, only secondary along with the AC pressure switch

Also, Are we sure the fan itself is not just dead? Is there a way to apply voltage to it directly to see if it runs?

 

Again, a carb'd/tbi engine has no ECM fan control. You can put a million new stock fan switches back in, they will all turn on at the same temp... 238°F (± a few degrees tolerance). CTS is irrelevant to a non-ecm controlled fan. I agree to your point of taking car to a mechanic over a stock/normal operating issue, though.

A carb'd/tbi car is single fan. In 87, the secondary fan (if equipped) was dead unless triggered by the fan switch, only.

Same guy... https://www.thirdgen.org/forums/cool...hermostat.html
______________
1987 helms service...

 

I don't think the original poster ever confirmed whether it's a TPI or TBI set up when i asked earlier unless I missed it somewhere. However if it is single fan then u can definitely ignore my last post hah.

 

The car only has a single fan system. Also, I'm sure the fan motor is in burnt out because the fan comes on when I run the AC. However, air-conditioning doesn't work, and I'm not sure whether this is due to a discharged AC system or some other problem because the compressor doesn't spin when the AC is turned on.
And how could I use a voltmeter to test the switch?

 

Someone Bump!!

I'm almost in the same boat as thomas here.... Is there a way to test the fan switch as well? Only way I can think of is taking a lighter or something to it with it plugged in to see if it kicks the fan on at all. Does that fan switch need to be fully threaded into the head also to make for good grounding? I can't see why the fan doesn't kick over if grounding the wire to metal or turning the a/c on kicks the relay on and gets the fan to turn. I also have a single fan system and haven't replaced the CTS or anything else but the fan switch and spliced in a new connector (which I know works cause I've tested it). Maybe we've got faulty "new" switches??

 

To Test the fan switch,........

https://www.thirdgen.org/forums/cool...an-switch.html

 

Hey John,

Thanks for the post.. helpful stuff. I still think I'm going to try it my way first and just heat the switch up while it's plugged into the connector. Should technically work (as it should normally). I don't want to mess with with all the wires and pliers and such. I'll test the "bad" switch that I've pulled out already and see what happens with it. I don't want to pull the new switch from the head just yet since it really is a pain in the a$$ to get to. I'm hoping I end up with your results at least one way or another ha

 

All right fellas,

Sorry to high jack your post tom and did you fix your issue yet? Any who, over the weekend I decided to test the "old" fan switch and to some success it worked... sort of. I vise gripped a lead from the threads of the switch to the ground of the battery, plugged the connector in, and turn the key over. I then used my mini butane soldering pen and heated the switch up slowly and then BAM the fan started to turn but only for a mere moment... My car has had its VATS system disabled with ohm resistors (from the previous owner), so I'm not sure if and when the fan started to kick on triggered something or if the VATS system finally kicked in that the fan shut off and everything went dead.

The interesting part is that after I let the car sit for a few minutes to reset the VATS lights and everything I wasn't able to re-create the result I had from the first test. Now, I haven't had another chance at it yet to see if I could yield the same results from the first go around and I haven't pulled the new switch from the head yet because of the busy weekend...

I guess my questions are, could the old switch operate correctly at all if it were "broken"? And assuming the new switch is good, why wont it kick the fan over now?

Do both heads need a ground wire to the chassis somewhere? I thought the driver head had a ground to the firewall that took care of the entire block?

I know the possibility of my temp gauge being off is highly probable but without a infrared therm I can't tell where my temps at for certain yet.

Any thoughts would be great because I'm puzzled at the moment.