After doing a search, I have found some conflicting information about what is causing my radiator fan malfuntion.

I have a 91 Firebird with the 305 TBI with only one fan behind the radiator.

There are three relays near the firewall, two on the drivers side, one on the passenger side near the A/C condeser.

I bought a new fan realy and installed it in all three different places, but the fan won't come on unless I turn thr air conditioner on, which hasn't actually worked in years. (the controls still work and the compressor cuts on, but no cold air-different problem)

One post said the relay for the fan goes up near the radiator, but I have no such relay there.

I'm going to replece the fan temperature switch next, as I have alrady replaced the engine coolant temperature sensor not too long ago.
(If it broke again, it should throw a trouble code, I think. That's how I figured out to replace it last time. My computer shows no trouble codes.)

From what I've read, the fan temperature switch is on the engine block somewhere near the knock sensor, but I didn't see anything there but the knock sensor.

I have already replced the thremostat.

The fan motor is not burt out, it comes on with the A/C.

The fan switch MUST be the problem, but I dunno where it is. If not, what else could it be? I'd rather not have to install a manual switch.

Thank you for taking the time to read all this. Any suggestions or additional info would be helpful.

-Jason!

 

I think it plugs into the head on the pass side. The switch that is

 

yeah u seemed to narrow it down to the fan switch if anything.

yup fan switch is on the passengers side engine block between 6 & 8 cylinders, way up there around the exhaust manifold.




its the gold sensor thing next to that one spark plug.

 

heres a picture of your fan switch.

 

whoops sorry I hit the button before adding the pic.
That the location of it not the way it looks I just added an elbow so it wouldnt hit my headers, but thats where it is at.

 

Thank you guys a lot for the pics! My car came with headers that take up a lot of room, so I'll have to get it from underneath. (The headers have the AIR tubes on them)

In the event that it's not the fan switch, are there any in-line fuses that I should look for? My fude box fuses are all good.

Thank you again.

 

the one in the cylinder head is for temp guage not fan

the oen for ecm/fan is in intake or in thermostat housing depending on year and engine and is two wire temp fan sensor switch and only available at GM parts counter

 

Randy,
My name is Tim, and I just recently got a 1989 firebird formula 350.....having trouble finding the cooling fan switch that is supposed to be above starter between 6 and 8. No where to be found............only thing I see is a plugged hole between 6 and 8. Do all formula 350s have this switch? All this is new to me, and I appreciate your help.

 

The one in the drivers side head is for the gauge, the one in the passenger side head is for the fan(s).

Sara Lou

 

The relay passes power to the fan when the control lead is grounded. It's grounded by either the fan switch or a switch in the A/C circuit (sometimes a pressure switch, sometimes at the control head). If your fan came on when the A/C was on, the relay is operating fine and doesn't need to be replaced.

If you can't identify which relay it is you can do a continuity check from the fan power wire back to the relay to be certain.

Your problem is somewhere in the control wiring to the fan switch. Pull the lead off the switch and with engine in run ground it. The fan should come on. If it doesn't check your continuity from that wire back to the relay control lead, the wire could be open.

The problem 'could' be the switch but it's pretty much the simplest piece in this system. Is your engine actually reaching the temp at which the switch should close? It's pretty high. Have you verified this?

 

I have a quick question... I own a 91 z28 5.0 TPI, and I was wondering why only one fan is running while my engine is running... when it reaches maybe about 265, the second fan does not turn on... could it be the fan switch or maybe a faulty ground?

 

First thing if your hitting 265 deg. your runnin WAY too hot, but the dual fans are simple. The driver side fan is your main cooling fan, it's the one the comes on normally to cool engine. The passenger side fan is designed to come on ONLY when the engine reaches a certain temperature (I think it's 200deg. or so) AND with the A/C on AND when the A/C reaches a certain pressure inside the system. I bypassed got rid of that crap and wired the passenger side fan into the drivers side fan and it runs both together and works tons better. hope that helped

 

Do you have a picture of how you wired the 2 fans together?

I am having a problem that my passenger fan won't come on at all. Thought is was the motor... Got a new motor and before I installed my buddy jumped the relay and the fan came on.

So I bought a new relay and nothing. Even when I turn the air on only the drivers side fan comes on. Looked at the fan switch on the passenger's side and it looks like my hookers fried it.

So at this point I just want to wire it and not have anymore issues.

 

On a dual fan setup the driver side fan is controlled by the temp sensor in the intake and the ecm. The driver fan will turn on(if factory specs) around 230 degrees. The fan switch in the pass. head controls the pass. side fan if the driver side fan fails to turn on and the pass. side fan will turn on around 240 degrees.

 

yeah i'll take some pics for you and get them to you...it's pretty easy hook up....basically what I did was take the two wires going to the secondary fan and splice them into the power and ground of the primary fan, right there at the fan itself...i'll get some pics though.....the secondary fan only comes on if all of the following apply, the engine is at a high temperature like 200-210 AND the A/C is on AND the pressure in the A/C system reaches a specific pressure...which means it doesn't come on often...but i have had no more problems in wiring the fans together. i'll get back with ya when i have some pics.

 

no that is a knock sensor i believe guys

 

Nah, two years later it's still the fan switch. KS is lower in the block.

 

dont even get me started on fan issues... my secondary fan is the only one that runs and i have it running all the time. it keeps my car at a lil under 220 or right around there but never over. If I told you guys how I did it you would **** yourselves.

 

Guys,
Im just getting to My Fan switch. Definately need to get it from under the car. I dont have a wrench that fits. Im getting one tonight. Before I do. does anyone know if an open ended wrench will fit up there (too long?). a Socket wont fit because of the Brace that is in the way (or do I need to remove that brace).
I couldnt get a short cresent on it last night because of the heat sheild. By the way I got a 5.7. thanks for any suggestions.

 

I'm having the same issue with my car, the fan's not coming on. Replaced the thermostat, coolant sensor and fan motor. I bought a relay but I think I plugged it into the wrong place. I'm going to see what's up this weekend. Not sure what else it could be if it's not the relay. What's the difference between a relay and relay switch?